University of Groningen Adverse life events and overweight in childhood, adolescence and young adulthood Elsenburg, Leonie Koosje

Adverse life events and overweight in childhood, adolescence and young adulthood Elsenburg, Leonie Koosje

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Elsenburg, L. K. (2018). Adverse life events and overweight in childhood, adolescence and young adulthood. Rijksuniversiteit Groningen.

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Overweight!and!obesity!are!a!major!public!health!problem.!Better!insight!into!the!causes!of! overweight! and! obesity! is! crucial! to! prevent! and! reduce! the! burden! of! overweight! and! obesity.! Early! childhood! factors,! even! factors! in! fetal! life,! are! involved! in! overweight! and! obesity!development,!in!children!as!well!as!adults.!In!this!dissertation!the!relation!between! adverse! life! events! and! overweight! and! obesity! in! childhood,! adolescence! and! young! adulthood!is!examined.!!

In! this! introduction,! I! will! highlight! the! prevalence! and! burden! of! overweight! and! obesity,! the! relation! between! overweight,! obesity! and! body! mass! index! (BMI)! and! the! persistent! nature! of! overweight! and! obesity.! Subsequently,! causes! of! overweight! and! obesity!will!be!discussed!and!a!model!of!childhood!overweight!and!obesity!development!will! be!presented.!Next,!the!possible!association!between!psychosocial!stressors!and!overweight! and!obesity!is!explored.!Special!attention!will!be!given!to!adverse!life!events,!a!specific!type! of! psychosocial! stressors,! and! childhood! abuse,! a! specific! type! of! adverse! life! event.! The! general!research!questions!of!this!dissertation!are!subsequently!presented.!Several!factors! that! may! be! involved! in! or! that! may! influence! the! relation! between! childhood! abuse! and! BMI! are! discussed.! This! introduction! will! conclude! with! the! presentation! of! the! cohort! studies!used!in!this!dissertation!and!a!chapterKbyKchapter!description!of!this!dissertation.!! !

OVERWEIGHT!AND!OBESITY!

In!the!last!couple!of!decades,!the!prevalence!of!overweight! and! obesity! among! children! and! adolescents! in! developed! countries!has!risen!dramatically![1].!In!1980,!approximately! 17%!of!children!and!adolescents!in!developed!countries!had!

overweight!or!obesity.!In!2013,!this!number!had!risen!to!23%.!In!the!Netherlands,!at!that! time! 14%! of! children! (2K21! years)! had! overweight! and! 2%! had! obesity! (Figure! 1)! [2].! This! constituted! a! 2K4! times! increase! for! overweight! prevalence! and! a! 4K6! times! increase! for! obesity! prevalence! compared! to! 30! years! earlier.! In! addition! to! an! overall! increase! in! overweight! and! obesity! prevalence,! an! increase! in! the! relative! proportion! of! children! and! adolescents!with!obesity!was!thus!also!apparent![2].!Although!prevalence!rates!of!childhood! overweight!and!obesity!in!the!Netherlands!are!high!with!about!one!sixth!of!this!population! suffering!from!these!conditions,!they!are!low!compared!to!other!developed!countries![1–3].! The!prevalence!of!childhood!overweight!and!obesity!in!the!United!States!is!much!higher![3].! In!2012,!the!combined!prevalence!of!overweight!and!obesity!among!children!(2K19!years)!in! the! United! States! was! 32%,! with! the! prevalence! of! obesity! being! around! 17%! [4].! Overweight!and!obesity!rates!in!young!adults!are!even!higher.!Nearly!60%!of!young!adults! (20K39!years)!in!the!United!States!had!overweight!in!2012!and!half!of!these!individuals!even! had!obesity![4].!In!the!Netherlands,!22%!of!young!adults!(18K34!years)!had!overweight!and! Overweight*and*obesity*2* “Abnormal'or'excessive'fat' accumulation'that'may' impair'health”'[86]*

8%!had!obesity!in!2016![5].!! !

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Figure! 1.! Overweight! and! obesity! prevalence! in! girls! and! boys! (2K21! years)! in! the! Netherlands! in!

1980,!1997!and!2009!(From!Schönbeck!et'al.,!2011)![2].! !

!

BODY!MASS!INDEX!

As! a! proxy! for! overweight! and! obesity,! body! mass! index! (BMI)! is! often! used.! BMI! is! a! measure! of! relative! weight! for! height,! calculated! by! dividing! an! individuals’! weight! in! kilograms!by!the!square!of!their!height!in!meters!(kg/m2_{).!This!measure!is!often!said!to!be!an!} imperfect! proxy! for! overweight! and! obesity! because! it! does! not! distinguish! between! fat!

mass!and!lean!mass,!such!as!muscles![6–8].!Still,!it!has!been! shown!to!serve!as!a!valid!measure!of!fatness!in!children!and! adolescents! [9,10].! Moreover,! other! indicators! of! overweight! and! obesity,! such! as! body! fat,! are! often! too! difficult,!expensive!and!time!consuming!to!measure!in!large! studies! using! adequate! methods,! such! as! air! displacement! plethysmography,! hydrostatic! weighing! and! dual! energy! XK ray!absorptiometry![11].!Measurement!of!height!and!weight! is! safe,! easy! and! inexpensive! and! therefore! BMI! is! often! a! preferred! indicator! of! overweight! and! obesity! in! studies! involving! many! participants! [10].! Adults! are! classified! as! having!overweight!when!their!BMI!is!25!kg/m2_{!or!higher!and!}

classified!as!having!obesity!when!their!BMI!is!30!kg/m2!or!higher.!For!children!no!general!cutK offs!exist,!since!body!mass!index!in!children!is!dependent!upon!age!and!gender!(Figure!2).!In! Figure! 2,! it! can! be! seen! that! the! cutKoffs! for! overweight! and! obesity! in! children! decrease! until!the!age!of!6!years!and!they!gradually!increase!after!this!age.!!

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Figure!2.!BMI!cutKoffs!for!overweight!(≥25!kg/m2_{!at!18!years)!and!obesity!(≥30!kg/m}2_{!at!18!years)!in!} 2K18!year!females!and!males.!The!cutKoffs!are!from!the!International!Obesity!Task!Force!(IOTF).!The! cutKoffs! are! originally! described! in! Cole! et' al.' (2000)! (solid! line)! and! extended! in! Cole! &! Lobstein! (2012)!(dashed!line)!(Figure!is!adapted!from!Cole!&!Lobstein,!2012)![12,13].!

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BURDEN!OF!OVERWEIGHT!AND!OBESITY!

A! higher! childhood! BMI! is! related! to! the! occurrence! of! diseases! such! as! type! 2! diabetes,! hypertension! and! coronary! heart! disease! in! adulthood! [14].! Further,! children! with! obesity! are! more! likely! to! suffer! from! low! selfKesteem! and! behavioral! problems! than! children!

BMI$ (k g/ m 2 )$ BMI$ (k g/ m 2)$ 20$ 25$ 30$ 20$ 25$ 30$ Age$(years)$ Age$(years)$ 2 6 10$ 14$ 18$ 2 6 10$ 14$ 18$ Female$ Male$ 25$ _25$ 30$ 30$ Body*mass*index'='' “A'person's'weight'in' kilograms'divided'by'the' square'of'height'in'meters.' A'high'body'mass'index' (BMI)'can'be'an'indicator'of' high'body'fatness.'BMI'can' be'used'to'screen'for'weight' categories'that'may'lead'to' health'problems'but'it'is'not' diagnostic'of'the'body' fatness'or'health'of'an' individual”'[87]'

without!obesity![15,16].!Except!for!in!Asia!and!SubKSaharan!Africa,!high!BMI!is!now!among! the! top! risk! factors! of! disease! worldwide! [17].! Besides! being! related! to! physical! and! psychological! morbidity,! overweight! and! obesity! in! childhood! and! adolescence! are! also! associated!with!premature!mortality!in!adulthood![14,18].!Globally,!high!body!mass!index!is! estimated!to!cause!about!3.5!million!deaths,!be!responsible!for!about!4.0%!of!life!years!lost! and! be! responsible! for! an! equal! percentage! of! disabilityKadjusted! life! years! (DALYs)! [17].! Overweight!and!obesity!thus!carry!a!huge!health!burden.!

! Overweight! and! obesity! also! impose! a! large! economic! burden! on! individuals! and! societies.! Obesity! in! adolescence! and! young! adulthood! has! an! adverse! effect! on! the! economic!situation!of!the!individual!by!being!related!to!a!lower!educational!attainment!and! lower!income![16,19].!The!economic!burden!of!childhood!and!adolescent!obesity!on!society! consists!of!direct!costs!of!obesityKrelated!healthcare!use,!indirect!costs!of!loss!of!productivity! of!parents!or!guardians!as!well!as!direct!and!indirect!costs!of!obesityKrelated!morbidity!and! mortality!in!adulthood![20].!Prevention!of!overweight!and!obesity!would!thus!go!beyond!the! immediate!benefits!of!reducing!disease!rates!and!would!substantially!reduce!medical!as!well! as!indirect!costs!of!overweight!and!obesity![21].! ! TRACKING!OF!OVERWEIGHT!AND!OBESITY!

The! association! between! childhood! obesity! and! adulthood! disease! partly! results! from! the! association!of!childhood!obesity!with!adulthood!obesity![14].!Children!who!have!overweight! or!obesity!are!likely!to!have!overweight!or!obesity!as!adults![22,23].!It!is!estimated!that!20K 60%!of!adolescents!with!overweight!also!has!overweight!in!adulthood!and!that!25K90%!of! adolescents!with!obesity!has!overweight!or!obesity!in!adulthood![23].!The!phenomenon!that! children!with!overweight!or!obesity!are!likely!to!have!overweight!or!obesity!in!adulthood!is! known!as!tracking!of!overweight!and!obesity!from!childK!to!adulthood.!The!high!prevalence! of!tracking!warrants!prevention!of!overweight!and!obesity!in!childhood!and!adolescence.!!

Adolescence! is! a! particularly! interesting! period! to! study! factors! associated! with! changes! in! BMI,! as! individuals! undergo! major! social,! emotional! and! physical! transitions! in! this!life!phase![24].!In!adolescence,!health!behaviors!may!change!as!they!increasingly!come! under! the! control! of! the! adolescent! rather! than! the! adolescent’s! parents! [25].! Obesity! prevalence! has! been! shown! to! increase! dramatically! as! adolescents! become! young! adults! [26].! Moreover,! adolescent! obesity! is! more! likely! to! track! into! adulthood! than! childhood! obesity![27].!The!fact!that!relatively!few!adolescents!with!obesity!no!longer!have!obesity!in! young!adulthood!shows!the!importance!of!obesity!prevention!in!and!before!this!life!phase! [28].!

!

DETERMINANTS!OF!OVERWEIGHT!AND!OBESITY!

Overweight! and! obesity! are! caused! by! an! imbalance! between! energy! intake! and! energy! expenditure![29].!When!the!intake!of!energy!exceeds!the!expenditure!of!energy,!this!excess! energy!is!stored!in!the!body!as!fat!and!when!this!occurs!repeatedly!overweight!and!obesity! arise.! In! a! statement! in! 2003,! the! American! Academy! of! Pediatrics! (AAP)! encouraged! pediatricians!to!“incorporate!assessment!and!anticipatory!guidance!about!diet,!weight,!and! physical! activity! into! routine! clinical! practice”! [30].! Physical! activity,! dietary! intake! and! patterns! and! sedentary! behavior! have! been! associated! with! overweight! and! obesity,! but! evidence! on! these! factors! having! a! strong! causal! relation! with! overweight! and! obesity! is! limited! [31–34].! The! number! of! factors! associated! with! obesity! indeed! is! larger! and! more! diverse! than! these! three! behaviors! [30].! Moreover,! the! association! of! factors! with! overweight!and!obesity!is!often!dependent!upon!the!presence!or!absence!of!other,!tertiary,! factors.!For!example,!tracking!of!obesity!from!childK!to!adulthood!is!more!likely!in!individuals! who!have!at!least!one!obese!parent![16].!!

To!illustrate!that!overweight!and!obesity!are!the!result!of!many!interacting!factors!at! multiple! levels,! Davison! and! Birch! applied! the! Ecological! Systems! Theory! (EST)! to! the! development!of!overweight![35].!The!application!of!the!EST!to!overweight!development!can! be! used! as! a! general! framework! to! study! the! development! of! overweight! and! obesity.! According! to! EST! human! development! can! be! explained! from! an! interactive! contextual! perspective,! meaning! that! the! different! contexts! in! which! an! individual! develops! and! the! interactions! within! and! among! these! contexts! needs! to! be! taken! into! account! if! one! is! to! explain! developmental! processes! of! an! individual.! The! context! in! which! an! individual! develops! is! its! immediate! environment:! the! family,! school,! community! and! neighborhood,! but!also!the!wider!environment:!the!society.!In!Figure!3!Davison!and!Birch’s!application!of! the! EST! to! overweight! development! is! shown.! It! can! be! seen! that! parental! weight! status,! parental! habits,! peers,! policies! and! knowledge! can! all! contribute! and! interact! with! each! other! and! with! other! factors! to! cause! overweight! and! obesity.! The! more! proximal! determinants! are! the! health! behaviors! associated! with! overweight! and! obesity! development:! dietary! intake,! physical! activity! and! sedentary! behavior,! and! child! characteristics! associated! with! overweight! and! obesity! development,! such! as! age! and! gender.! In! the! two! most! outer! shells,! more! distal! determinants! are! placed:! parenting! characteristics,! demographic! characteristics! and! community! characteristics.! Besides! being! directly!related!to!overweight!and!obesity!development,!the!factors!in!the!model!can!also!be! related! to! overweight! and! obesity! development! in! interaction! with! each! other! and! with! other!factors.!!

! !

Figure!3.!Ecological!model!of!predictors!of!childhood!overweight!as!developed!by!Davison!and!Birch!

(From!Davison!&!Birch,!2001)![35].!!

=! Child! risk! factors! (shown! in! upper! case! lettering)! refer! to! child! behaviors! associated! with! the! development!of!overweight.!Characteristics!of!the!child!(shown!in!italic!lettering)!interact!with!child! risk! factors! and! contextual! factors! to! influence! the! development! of! overweight! (i.e.! moderator! variables).!

!

Application!of!the!EST!to!the!development!of!overweight!and!obesity!emphasizes!the! importance! of! considering! the! environment! in! which! a! child! grows! up! in! overweight! and! obesity!research.!However,!the!list!of!determinants!in!Figure!3!is!by!no!means!exhaustive.! For! example,! a! child! characteristic! that! could! play! an! important! role! in! overweight! and! obesity! development! is! the! psychological! makeup! of! a! child.! Children! with! certain! personality! traits! [36,37]! or! with! a! mental! health! disorder,! such! as! depression,! are! more! likely!to!develop!overweight!and!obesity!as!well![38–42].!!

Another! important! factor! to! consider! with! regard! to! overweight! and! obesity! development! is! socioKeconomic! status! [43,44].! Children! with! a! low! socioKeconomic! status! are! more! likely! to! develop! overweight! and! obesity! and! have! a! higher! BMI.! Low! socioK economic!status!is!related!to!overweight!and!obesity!development!via!other!factors,!such!as! the!types!of!foods!available!in!the!home![45].!A!low!socioKeconomic!status!is!an!example!of!a! psychosocial! stressor! [44].! Psychosocial! stressors! are! psychologically! distressing! events,!

CHILD& WEIGHT& STATUS& Child&characteris8cs&& and&child&risk&factors*& Paren8ng&styles&and&& family&characteris8cs& Community,&demographic& and&societal&characteris8cs& Ethnicity( School(lunch(( programs( Work(hours( Leisure(7me( Accessibility(of(( recrea7onal(facili7es( Accessibility(of(convenience( (foods(and(restaurants( Family(leisure( 7me( School(physical(( educa7on(( programs( Crime(rates(and( neighborhood(( safety( Socioeconomic( status( Child(feeding(( prac7ces( Types(of(foods( available(in(the( (home( Nutri7onal(( knowledge( Parent(( dietary(intake( Parent(food( preferences( _{Parent(weight((} status( Parent(encouragement(of( child(ac7vity( Parent(ac7vity(( paCerns( Parent(preference(( for(ac7vity( Parent(( monitoring(of(( child(TV(viewing( Family(TV(( viewing( Peer(and(sibling( (interac7ons( Gender& Age& Familial&suscep2bility&to& weight&gain& DIETARY( (BEHAVIOR( SEDENTARY( (BEHAVIOR( PHYSICAL(( ACTIVITY(

situations!or!circumstances!that!are!social!in!nature![46].!Psychosocial!stressors!can!threaten! an!individual’s!mental!and!physical!wellKbeing![47].!Other!examples!of!psychosocial!stressors! are!loneliness,!job!strain!and!adverse!life!events,!such!as!childhood!abuse,!death!of!a!friend! or!family!member!and!parental!divorce.!! ! PSYCHOSOCIAL!STRESSORS! Psychosocial!stressors!can!also!influence!weight.!Weight!can! be! influenced! via! two! different! mechanisms! [46,48].! The! first! mechanism! is! by! influencing! health! behaviors,! such! as! dietary!intake,!physical!activity!and!sedentary!behavior.!The!

second!mechanism!is!via!alterations!in!biological!reactions!in!the!body.!Health!behaviors!can! be!influenced,!because!the!availability!of!resources!can!be!influenced:!children!from!a!low! socioKeconomic!status!have!fewer!resources!to!join!sports!clubs!and!eat!healthy!foods!and! often! live! in! less! safe! neighborhoods! with! less! opportunities! for! outdoor! play! [45,49,50].! Secondly,!health!behaviors!can!be!influenced,!because!they!can!serve!as!a!method!of!coping! with! the! psychosocial! stressor.! Eating,! especially! eating! unhealthy! foods,! can! alleviate! feelings! of! stress! [51–53].! Thirdly,! health! behaviors! can! be! influenced,! because! biological! reactions!in!the!body!may!be!altered.!One!such!a!reaction!is!the!stress!response.!When!the! stress!response!is!triggered,!the!hypothalamusKpituitaryKadrenal!axis!(HPA!axis)!is!activated,! ultimately!causing!the!release!of!cortisol!(Figure!4).!Chronically!elevated!cortisol!is!suggested! to!lead,!via!effects!on!other!hormones,!to!increased!appetite!and!food!intake,!especially!of! unhealthy! foods! [51,53,54].! In! addition! to! changing! food! intake! and! thereby! changing! weight,! biological! reactions! in! response! to! psychosocial! stressors! can! also! influence! the! body’s! internal! biology! and! weight! directly! [44,55].! For! example,! cortisol! released! in! the! body!in!response!to!stress!can!increase!fat!deposition!in!the!body!by!stimulating!the!uptake! and!inhibiting!the!release!of!free!fatty!acids!by!adipose!tissue!(i.e.!fat)![53].!!!!!

!

ADVERSE!LIFE!EVENTS!

As!mentioned,!socioKeconomic!status!is!only!one!type!of!psychosocial!stressor.!Adverse!life! events! are! another! type! of! psychosocial! stressor.! Adverse! life! events! are! events! such! as! parental! divorce,! the! illness! or! death! of! a! family! member,! and! the! experience! of! being! bullied.!Another!important!adverse!life!event!is!the!experience!of!abuse!in!childhood.!These! different!adverse!life!events!have!different!prevalence!rates![56].!These!different!events!also! likely! have! a! different! impact! on! individuals! [56].! However,! regardless! of! the! differences! between! events,! they! are! assumed! to! influence! children’s! weight! status! via! the! same! mechanisms!as!other!psychosocial!stressors![56].!! ! Psychosocial*stressors'='' “External'events'or' conditions'that'threaten'an' individual’s'well=being”'[47].''

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! Figure!4.!The!hypothalamicKpituitaryKadrenal!axis!(HPA!axis).!The!hypothalamus!is!under!the!control! of!the!hippocampus!and!the!amygdala.!When!the!HPA!axis!is!triggered,!the!paraventricular!nucleus! (PVN)!in!the!hypothalamus!releases!corticotrophin!releasing!factor!(CRF).!CRF!stimulates!the!anterior! pituitary!to!release!adrenocorticotropic!hormone!(ACTH).!ACTH!moves!through!the!bloodstream!to! the! adrenal! cortex,! where! it! stimulates! the! release! of! glucocorticoids! (cortisol! in! humans).! Glucocorticoids! provide! negative! feedback! to! and! slow! down! the! release! of! hormones! from! the! hippocampus,! hypothalamus! and! pituitary! to! shut! down! the! HPA! axis! (From! Hyman,! 2009! by! Kim! Caesar! [57].! Reprinted! by! permission! from! Springer! Nature:! Nature,! Nature! Neuroscience,! How! adversity!gets!under!the!skin,!Hyman!SE,!copyright!2009).!

!

Indeed,! adverse! life! events! have! been! related! to! weight! status.! The! experience! of! adverse!life!events!has!been!related!to!obesity!in!adulthood.!Adults!who!reported!more!than! four!adverse!childhood!experiences!were!more!likely!to!have!severe!or!morbid!obesity!than! adults!who!reported!no!adverse!childhood!experiences![58,59].!In!addition,!they!were!more! likely! to! display! physical! inactivity! as! well! [58].! While! there! seems! to! be! an! association! between!adverse!life!events!and!weight!status!in!adulthood,!it!is!unclear!whether!there!is!an! association!between!adverse!life!events!and!measures!of!overweight!and!obesity!in!the!first!

decades!of!life.!Research!on!the!relation!between!accumulation!of!adverse!life!events!and! overweight,!obesity!and!BMI!in!childhood!has!resulted!in!mixed!findings.!Different!studies! have!employed!different!methods,!measuring!exposures!and!outcomes!differently,!resulting! in! unclear! associations.! The! association! between! adverse! life! events! and! BMI! in! children,! adolescents!and!young!adults!is!the!focus!of!this!dissertation.!!

The!effects!of!adverse!life!events!on!health!are!often!studied!by!examining!the!effect! of! accumulation! of! adverse! life! events.! This! is! usually! operationalized! as! the! number! of! experienced!adverse!life!events.!In!this!way,!it!can!be!established!whether!the!experience!of! more!adverse!life!events!is!related!to!health!deterioration.!Studying!the!effect!of!isolated! adverse!events!on!medical!conditions!is!suggested!to!overestimate!the!effect!of!that!event! due!to!its!potential!relation!with!other!adverse!events![56,60].!For!example,!individuals!who! reported! the! experience! of! one! type! of! childhood! abuse! (i.e.! sexual,! physical! or! verbal! abuse)!were!also!likely!to!report!the!experience!of!another!type!of!childhood!abuse![58].!In! addition,!individuals!who!reported!the!experience!of!substance!use!in!the!household!before! age!18!often!also!reported!violent!treatment!of!their!mother![58].!Studying!accumulation!of! adverse!events!rather!than!single!events!is!also!done!as!accumulation!of!adverse!events!is! more! likely! to! cause! chronic! stress,! and! set! the! aboveKmentioned! mechanisms! in! motion,! than! a! single! event! [61].! A! first! goal! of! this! dissertation! will! therefore! be! to! study! the! relationship!between!accumulation!of!adverse!events!and!BMI!in!children,!adolescents!and! young! adults.! The! aim! will! be! to! uncover! whether! and! when! the! relation! between! both! factors! manifests! itself! in! the! first! decades! of! life.! The! first! research! question! of! this! dissertation!is:! ! “Is'there'an'association'between'accumulation'of'adverse'life'events'and'measures'of' overweight'in'childhood,'adolescence'and'young'adulthood?”' ' To!examine!the!evidence!for!this!association!in!the!scientific!literature,!a!systematic! review!and!metaKanalysis!will!be!performed!into!the!association!between!accumulation!of! adverse!life!events!and!measures!of!overweight!in!childhood!and!adolescence!(chapter!2).! To! examine! whether! the! association! manifests! itself! in! a! particular! phase! during! the! first! decades!of!life,!the!association!between!accumulation!of!adverse!life!events!in!childhood,!at! the!beginning!of!adolescence!and!at!the!end!of!adolescence!with!measures!of!overweight!at! the!beginning!of!adolescence,!the!end!of!adolescence!and!the!beginning!of!young!adulthood! will!be!studied!(chapter!3).!It!will!also!be!examined!whether!the!association!is!present!only! for!specific!types!of!adverse!events,!such!as!events!regarding!the!health!of!participants!or! loved!ones.!Finally,!the!association!between!accumulation!of!adverse!life!events!in!childhood!

and!different!BMI!development!trajectories!from!adolescence!to!early!young!adulthood!will! be!studied!(chapter!4).! ! CHILDHOOD!ABUSE! Childhood!abuse!is!a!particular!adverse!life!event.!Childhood!abuse!is!shown!to!be!one!of!the! most!severe!adverse!events,!more!strongly!associated!with!conditions!like!depression!and! anxiety,! than! other! adverse! events! are! [62–64].! This! is! possibly! due! to! the! more! chronic! nature!of!childhood!abuse![64].!As!childhood!abuse!is!such!a!severe!adverse!life!event!with!a! specific! character,! studying! the! association! between! this! particular! adverse! life! event! and! BMI! is! important! and! can! provide! insightful! information! regarding! the! effects! of! other! adverse! life! events! in! childhood! on! BMI.! The! association! between! childhood! abuse! and! obesity!in!adulthood!has!been!extensively!studied!and!childhood!abuse!has!been!related!to! obesity! in! adults! [65,66].! However,! there! seems! to! be! no! association! between! childhood! abuse!and!obesity!in!childhood![65].!When!the!relation!does!come!to!expression!is!unclear.! Unraveling! whether! the! association! is! already! present! in! young! adulthood! will! provide! important! information! regarding! the! course! of! the! association! during! life.! Therefore,! the! second!research!question!of!this!dissertation!is:! ! “Is'childhood'abuse'associated'with'body'mass'index'in'young'adulthood?”' ! This!association!will!be!examined!in!a!dataset!of!Dutch!young!adults!(chapter!5)!and!young! adults!from!the!United!States!(chapter!6).! ! MECHANISMS!CONNECTING!ADVERSE!EVENTS!AND!BMI!

Other! factors,! such! as! health! behaviors! and! child! characteristics,! may! explain! or! may! influence!the!relation!between!childhood!abuse!and!BMI.!When!factors!are!involved!in!the! relation! as! explanatory! factors! connecting! childhood! abuse! and! BMI,! these! explanatory! factors!are!called!mediating!factors.!Mediating!factors!give!us!insight!into!the!mechanisms! that! connect! childhood! abuse! with! BMI.! As! previously! mentioned,! one! of! the! proposed! mechanisms! through! which! adverse! life! events! can! exert! an! effect! on! BMI! is! via! health! behaviors![46,48].!Health!behaviors!can!mediate!the!relation!between!childhood!abuse!and! BMI.!When!factors!influence!the!presence!or!size!of!the!relation,!they!serve!as!moderators! of!the!relation!between!childhood!abuse!and!BMI.!For!example,!sweet!food!intake!has!been! shown!to!moderate!the!relation!between!adverse!life!events!and!BMI:!in!children!with!high! sweet! food! intake! there! is! a! relation! between! adverse! life! events! and! BMI,! but! not! in! children! with! low! sweet! food! intake! [67].! Two! factors! that! may! be! of! importance! for! the! relation!between!childhood!abuse!and!BMI,!but!that!have!received!little!attention!thus!far,!

are!mental!health!conditions!and!personality.!The!mental!health!conditions!depression!and! anxiety!can!serve!as!mediators!of!the!relation!between!childhood!abuse!and!BMI![68].!This! means!that!childhood!abuse!could,!at!least!partially,!exert!an!effect!on!BMI!via!changes!in! depression! and! anxiety.! Personality! is! a! factor! that! could! serve! as! a! moderator! of! the! relation!between!childhood!abuse!and!BMI![69].!Someone’s!personality!characteristics!could! influence!whether!a!relation!between!childhood!abuse!and!BMI!is!present,!because!it!could! influence! one’s! appraisal! of! and! one’s! response! to! events! [70].! For! example,! a! relation! between! childhood! abuse! and! BMI! may! be! present! for! individuals! who! are! more! easily! distressed,!but!may!be!absent!for!individuals!who!are!less!easily!distressed.!In!line!with!this! idea,! the! association! between! adverse! life! events! and! daily! hassles! with! depressive! symptoms!is!stronger!in!individuals!with!high!levels!of!neuroticism!than!in!individuals!with! low!levels!of!neuroticism![71].!!

!

THE!ROLE!OF!DEPRESSION!AND!ANXIETY!DISORDERS!

While! there! is! a! relation! between! childhood! abuse! and! obesity! in! adulthood,! the! relation! does! not! seem! to! be! present! when! taking! into! account! depression! [65].! This! means! that! depression! could! explain! the! relation! between! childhood! abuse! and! BMI! in! adults:! childhood! abuse! could! be! related! to! a! higher! rate! of! depression! or! higher! depressive! symptoms! and,! in! turn,! depression! could! be! associated!with!higher!BMI.!Depression!could!thereby!serve! as!an!important!factor!connecting!childhood!abuse!and!BMI.! This!is!in!line!with!the!idea!that!psychosocial!stressors!could! be! related! with! changes! in! body! weight! via! mental! health! conditions![53,72].!This!is!also!in!line!with!studies!finding!a! relation!between!childhood!abuse!and!a!higher!occurrence! of!depression!and!anxiety!disorders!later!in!life![73–76]!and! with! studies! finding! a! prospective! relation! between!

depression! and! obesity! [38,41,42].! Prospective! evidence! on! the! relation! between! anxiety! disorders! and! obesity! is,! however,! limited! [77,78].! Nonetheless,! anxiety! disorders! are! suggested!to!play!a!role!in!the!relation!between!childhood!abuse!and!BMI!as!well![68].!As! mental! health! disorders! often! come! to! expression! before! adulthood,! studying! the! role! of! depression! and! anxiety! disorders! at! the! end! of! adolescence! in! the! relation! between! childhood!abuse!and!BMI!in!early!adulthood!is!of!particular!importance![79,80].!Depression! and! anxiety! disorders! in! adolescence! could! connect! the! occurrence! of! childhood! abuse! to!

Depression'–'' “A'range'of'mental' problems'characterized'by' loss'of'interest'and' enjoyment'in'ordinary' experiences,'low'mood'and' associated'emotional,' cognitive,'physical'and' behavioral'symptoms”'[88]' Anxiety*disorders'–'' “Disorders'marked'by' psychological'symptoms' such'as'excessive'worry,' fear,'apprehension,'and' physical'symptoms'such'as' fatigue,'heart'palpitations' and'tension”'[89]'

changes!in!BMI!in!young!adulthood.!To!examine!this!issue,!the!third!research!question!of!this! dissertation!is:! ! ! “Is'the'association'between'childhood'abuse'and'body'mass'index'in'young'adulthood' mediated'by'depression'or'anxiety'disorders?”' !

Mediation! of! the! association! between! childhood! abuse! and! BMI! by! major! depressive! disorder!(MDD)!and!generalized!anxiety!disorder!(GAD)!will!be!examined!using!a!dataset!of! Dutch!adolescents!followed!into!young!adulthood!(chapter!5).!!

!

THE!INFLUENCE!OF!PERSONALITY!TRAITS!

Another! psychological! factor! that! may! be! important! for! changes! in! BMI! to! occur! in! response! to! childhood! abuse! is! personality.! Personality! traits! have! been! related! to! the! development! of! obesity.! High! conscientiousness! (e.g.! the! tendency!to!be!organized,!prefer!order!and!be!persistent)!is!

associated! with! a! lower! obesity! risk! [36,37,81,82].! Neuroticism! (e.g.! the! tendency! to! experience! negative! emotions)! has! been! related! to! a! higher! risk! of! obesity! [37,81,83].! Besides!being!directly!related!to!obesity!development,!personality!traits!could!also!alter!the! relation! between! childhood! abuse! and! BMI.! Firstly,! personality! traits! could! influence! the! stress! response,! as! they! are! involved! in! evaluating! the! stressfulness! of! an! event! and! activating!the!response![53,70].!Secondly,!personality!could!influence!someone’s!behavior!in! response!to!adverse!events![70].!Whether!personality!traits!influence!the!relation!between! childhood! abuse! and! body! mass! index! is,! however,! unclear.! Thus,! the! fourth! research! question!of!this!dissertation!is:! ! “Is'the'association'between'childhood'abuse'and'body'mass'index'in'young'adulthood' moderated'by'personality'traits?”! ! Moderation!of!the!association!between!childhood!abuse!and!BMI!by!personality!traits!will! be!examined!in!a!nationally!representative!sample!of!young!adults!from!the!United!States! (chapter!6).!The!personality!traits!assessed!in!this!study!will!be!the!Big!Five!personality!traits! (i.e.!extraversion,!neuroticism,!agreeableness,!conscientiousness!and!openness).! ! ! ! Personality*traits'=' “Individual'differences'in' enduring'patterns'of' behavior,'emotion,'and' cognition”'[81]' '

COHORT!STUDIES!

For!this!dissertation,!data!from!two!different!cohort!studies!are!used.!One!of!these!studies!is! performed! in! the! Netherlands! and! the! other! is! performed! in! the! US.! Both! cohort! studies! recruited!adolescents!and!followed!them!into!young!adulthood.!!

!

TRAILS!

Most! of! the! studies! in! this! dissertation! are! based! on! data! of! the! TRAILS! (TRacking! Adolescents’!Individual!Lives!Survey)!cohort.!TRAILS!is!an!ongoing!prospective!cohort!study! on! the! psychological,! social! and! physical! development! of! Dutch! adolescents! and! young! adults.!The!main!aim!of!TRAILS!is!to!contribute!to!the!understanding!of!the!determinants!of! adolescents’! mental! health! and! social! development! during! adolescence! and! young! adulthood,!as!well!as!the!mechanisms!underlying!the!associations![84].!!

Children! were! recruited! for! participation! in! the! TRAILS! cohort! when! they! were! between!10!and!12!years!old![84,85].!The!cohort!included!children!born!within!two!1Kyear! periods!from!five!municipalities!in!the!North!of!the!Netherlands.!In!total,!2230!children!were! included! of! which! 51%! was! female.! Currently,! five! waves! of! data! collection! are! available.! These!waves!took!place!every!two!to!three!years!and!were!performed!between!March!2001! and!July!2002,!September!2003!and!December!2004,!September!2005!and!December!2007,! October! 2008! and! September! 2010! and! April! 2012! and! November! 2013.! At! these! waves,! mean!age!of!the!children!was!11.1!years,!13.6!years,!16.3!years,!19.1!years!and!22.3!years,! respectively!(Figure!5).!Height!and!weight!were!measured!by!trained!research!assistants!at! each!of!these!waves.!At!wave!1,!adverse!events!were!reported!by!parents!in!an!interview.!At! wave! 3! and! 5,! adolescents! reported! on! adverse! events! they! had! experienced! in! a! semiK structured! interview.! At! wave! 4,! adolescents! reported! on! the! occurrence! of! abuse! before! the!age!of!16!using!a!selfKadministered!questionnaire.!Additionally,!adolescents!underwent!a! mental! health! interview! at! wave! 4! to! assess! the! occurrence! and! timing! of! mental! health! disorders!before!this!time.!!! ! ! ! ! Figure!5.!Timeline!of!TRacking!Adolescents’!Individual!Lives!Survey!(TRAILS)! ! ! Wave%1%

11.1%years 13.6%years Wave%2% 16.3%years Wave%3% 19.1%years Wave%4% 22.3%years Wave%5%

2011$

2000$ 2001$ 2002$ 2003$ 2004$ 2005$ 2006$ 2007$ 2008$ 2009$ 2010$ 2012$ 2013$

Wave%1%

10(12%years 12(14%yearsWave%2% 14(18%yearsWave%3% 16(20%yearsWave%4% 20(23%yearsWave%5%

2011$

Add!Health!

The! final! study! in! this! dissertation! used! data! of! The! National! Longitudinal! Study! of! Adolescent! to! Adult! Health! (Add! Health).! Add! Health! is! an! ongoing! longitudinal! study! containing!a!nationally!representative!sample!of!adolescents!in!the!United!States.!The!main! aim!is!to!unravel!how!the!social!environment,!behaviors!and!mental!and!physical!wellKbeing! in!adolescence!and!young!adulthood!are!related!to!health!and!achievement!later!in!life.!!

In! the! 1994K1995! school! year,! adolescents! in! grades! 7K12! were! recruited! for! participation!in!the!Add!Health!study.!These!adolescents!were!recruited!through!their!high! schools.!At!baseline,!80!high!schools!in!the!United!States,!that!had!an!11th!grade!and!at!least! 30! students,! were! selected.! The! sampling! and! stratification! method! ensured! that! the! selected! high! schools! were! representative! of! US! high! schools! with! respect! to! region,! urbanicity,!size,!school!type!and!ethnic!compilation.!For!each!high!school!that!did!not!have!a! 7th!grade,!one!of!its!feeder!schools!(a!school!sending!at!least!5!graduates!to!that!high!school)! was! selected! with! a! probability! proportional! to! the! number! of! graduates! it! delivered.! In! total,!132!schools!were!included!at!baseline.!Students!in!each!school!were!stratified!by!grade! and! sex! and! from! each! stratum! approximately! 17! adolescents! were! selected! for! inKhome! interviews.! Specific! minority! groups! were! oversampled.! In! total,! 20,745! students! were! recruited!for!the!inKhome!interviews!at!baseline.!The!Add!Health!study!was!approved!by!the! institutional!review!board!of!the!University!of!North!Carolina,!Chapel!Hill.!!

At! the! moment,! 4! waves! of! data! collection! have! been! completed.! Wave! 2! was! performed! in! 1996! and! wave! 3! in! 2001K2002.! In! this! dissertation,! data! of! wave! 4! is! used.! Wave!4!was!conducted!in!2008!when!participants!were!between!24K32!years!old!(Figure!6).! At!wave!4,!interviewers!measured!height!and!weight!and!participants!provided!information! on! the! occurrence! of! abuse! before! the! age! of! 18! and! on! their! personality! in! a! selfK administered!questionnaire.! ! ! ! Figure!6.!Timeline!of!The!National!Longitudinal!Study!of!Adolescent!to!Adult!Health!(Add!Health)! ! OUTLINE!OF!THIS!DISSERTATION!

The! outline! of! this! dissertation! is! depicted! in! Figure! 7.! The! association! between! accumulation!of!adverse!life!events!and!BMI,!overweight!and!obesity!is!examined!in!the!first!

Wave%1%

Grades%7,12 Grades%8,12Wave%2% 18,26%yearsWave%3% 24,32%yearsWave%4%

2005$

part! of! this! dissertation.! In! chapter! 2,! the! existing! evidence! for! a! relation! between! accumulation! of! adverse! life! events! and! measures! of! overweight! in! childhood! and! adolescence!is!examined!by!means!of!a!systematic!review!and!metaKanalysis.!All!available! evidence! from! observational! studies! is! summarized! and! the! estimates! from! the! different! studies!are!pooled!to!show!the!overall!association.!In!chapter!3,!a!longitudinal!investigation! into!the!prospective!associations!between!accumulation!of!adverse!life!events!in!childhood,! at!the!beginning!of!adolescence!and!at!the!end!of!adolescence!with!BMI!at!the!beginning!of! adolescence,!in!adolescence!and!in!early!young!adulthood!is!described.!The!study!in!chapter! 4! investigates! the! general! BMI! development! trajectories! from! adolescence! to! early! young! adulthood!and!investigates!the!association!of!accumulation!of!adverse!life!events!with!these! BMI!trajectories.!This!study!serves!to!examine!whether!unhealthy!BMI!development,!and!the! association!of!accumulation!of!adverse!life!events!with!unhealthy!BMI!development,!can!be! detected!at!an!early!stage.!The!remainder!of!the!dissertation!is!concerned!with!examination! of! the! relation! between! childhood! abuse! and! BMI! in! young! adulthood! and! with! the! identification!of!psychological!factors!that!may!serve!an!explanatory!or!moderating!role!in! this! relation.! In! chapter! 5,! it! is! examined! whether! depression! and! anxiety! at! the! end! of! adolescence! explain! part! of! the! relation! between! childhood! abuse! and! BMI! in! young! adulthood.! In! chapter! 6,! it! is! examined! whether! personality! traits! influence! the! relation! between! childhood! abuse! and! BMI! in! young! adulthood.! In! this! way,! it! can! be! established! whether! different! personality! traits! modify! the! relationship! between! childhood!abuse! and! BMI.! Chapter! 7! is! a! general! discussion! of! the! main! findings! of! this! dissertation! and! their! implications,! the! methodological! considerations! of! this! dissertation! and! the! directions! for! future!research.! ! ! ! Figure!7.!Outline!of!this!dissertation! !

DEPRESSION)AND)

ANXIETY)

PERSONALITY)

BODY)MASS)INDEX)

ABUSE)

ADVERSE)EVENTS)

OVERWEIGHT/OBESITY)

REFERENCES!

[1]! Ng! M,! Fleming! T,! Robinson! M,! et! al.! Global,! regional,! and! national! prevalence! of! overweight!and!obesity!in!children!and!adults!during!1980K2013:!a!systematic!analysis! for!the!Global!Burden!of!Disease!Study!2013.!Lancet!2014;384:766–81.!

[2]! Schönbeck!Y,!Talma!H,!van!Dommelen!P,!et!al.!Increase!in!prevalence!of!overweight!in! Dutch!children!and!adolescents:!a!comparison!of!nationwide!growth!studies!in!1980,! 1997!and!2009.!PLoS!One!2011;6:e27608.!

[3]! Wang! Y,! Lobstein! T.! Worldwide! trends! in! childhood! overweight! and! obesity.! Int! J! Pediatr!Obes!2006;1:11–25.!

[4]! Ogden!CL,!Carroll!MD,!Kit!BK,!et!al.!Prevalence!of!childhood!and!adult!obesity!in!the! United!States,!2011K2012.!JAMA!2014;311:806–14.!

[5]! Centraal! Bureau! voor! de! Statistiek! (CBS)! &! Rijksinstituut! voor! Volksgezondheid! en! Milieu!(RIVM).!Gezondheidsenquete/Leefstijlmonitor!CBS!en!RIVM!2016.!Available!at:! http://www.rivm.nl/Onderwerpen/L/Leefstijlmonitor/Cijfers/Gezond_gewicht.!

[6]! Ahima! RS,! Lazar! MA.! The! health! risk! of! obesity! K! better! metrics! imperative.! Science! 2013;341:856–8.!

[7]! Krakauer! NY,! Krakauer! JC.! A! new! body! shape! index! predicts! mortality! hazard! independently!of!body!mass!index.!PLoS!One!2012;7.!

[8]! Nevill! AM,! Stewart! AD,! Olds! T,! et! al.! Relationship! between! adiposity! and! body! size! reveals!limitations!of!BMI.!Am!J!Phys!Anthropol!2006;129:151–6.! [9]! Mei!Z,!GrummerKStrawn!LM,!Pietrobelli!A,!et!al.!Validity!of!body!mass!index!compared! with!other!bodyKcomposition!screening!indexes!for!the!assessment!of!body!fatness!in! children!and!adolescents.!Am!J!Clin!Nutr!2002;75:978–85.! [10]! Pietrobelli!A,!Faith!MS,!Allison!DB,!et!al.!Body!mass!index!as!a!measure!of!adiposity! among!children!and!adolescents:!a!validation!study.!J!Pediatr!1998;132:204–10.! [11]! Horan!M,!Gibney!E,!Molloy!E,!et!al.!Methodologies!to!assess!paediatric!adiposity.!Ir!J! Med!Sci!2015;184:53–68.!

[12]! Cole! TJ,! Bellizzi! MC,! Flegal! KM,! et! al.! Establishing! a! standard! definition! for! child! overweight!and!obesity!worldwide:!international!survey.!BMJ!2000;320:1240.!

[13]! Cole! TJ,! Lobstein! T.! Extended! international! (IOTF)! body! mass! index! cutKoffs! for! thinness,!overweight!and!obesity.!Pediatr!Obes!2012;7:284–94.!

[14]! Park!MH,!Falconer!C,!Viner!RM,!et!al.!The!impact!of!childhood!obesity!on!morbidity! and!mortality!in!adulthood:!A!systematic!review.!Obes!Rev!2012;13:985–1000.!

[15]! Puder! JJ,! Munsch! S.! Psychological! correlates! of! childhood! obesity.! Int! J! Obes! 2010;34:S37–43.!

[16]! Reilly! JJ,! Methven! E,! McDowell! ZC,! et! al.! Health! consequences! of! obesity.! Arch! Dis! Child!2003;88:748–52.!

[17]! Lim!SS,!Vos!T,!Flaxman!AD,!et!al.!A!comparative!risk!assessment!of!burden!of!disease! and!injury!attributable!to!67!risk!factors!and!risk!factor!clusters!in!21!regions,!1990– 2010:! a! systematic! analysis! for! the! Global! Burden! of! Disease! Study! 2010.! Lancet! 2012;380:2224–60.!

[18]! Reilly! JJ,! Kelly! J.! LongKterm! impact! of! overweight! and! obesity! in! childhood! and! adolescence!on!morbidity!and!premature!mortality!in!adulthood:!systematic!review.! Int!J!Obes!2011;35:891–8.!

[19]! Karnehed! N,! Rasmussen! F,! Hemmingsson! T,! et! al.! Obesity! and! attained! education:! cohort! study! of! more! than! 700,000! Swedish! men.! Obesity! (Silver! Spring)! 2006;14:1421–8.!

[20]! Lehnert!T,!Sonntag!D,!Konnopka!A,!et!al.!Economic!costs!of!overweight!and!obesity.! Best!Pract!Res!Clin!Endocrinol!Metab!2013;27:105–15.!

[21]! Wang! LY,! Denniston! M,! Lee! S,! et! al.! LongKterm! health! and! economic! impact! of! preventing! and! reducing! overweight! and! obesity! in! adolescence.! J! Adolesc! Heal! 2010;46:467–73.!

[22]! Simmonds! M,! Llewellyn! A,! Owen! CG,! et! al.! Predicting! adult! obesity! from! childhood! obesity:!a!systematic!review!and!metaKanalysis.!Obes!Rev!2016;17:95–107.!

[23]! Singh! AS,! Mulder! C,! Twisk! JWR,! et! al.! Tracking! of! childhood! overweight! into! adulthood:!A!systematic!review!of!the!literature.!Obes!Rev!2008;9:474–88.!

[24]! Viner! RM,! Ross! D,! Hardy! R,! et! al.! Life! course! epidemiology:! recognising! the! importance!of!adolescence.!J!Epidemiol!Community!Health!2015;69:719–20.! [25]! Daniels!SR,!Hassink!SG.!The!role!of!the!pediatrician!in!primary!prevention!of!obesity.! Pediatrics!2015;136:e275–92.! [26]! GordonKLarsen!P,!The!NS,!Adair!LS.!Longitudinal!trends!in!obesity!in!the!United!States! from!adolescence!to!the!third!decade!of!life.!Obes!(Silver!Spring)!2010;18:1801–4.! [27]! Whitaker!RC,!Wright!JA,!Pepe!MS,!et!al.!Predicting!obesity!in!young!adulthood!from! childhood!and!prental!obesity.!N!Engl!J!Med!1997;337:869–73.!

[28]! GordonKLarsen! P,! Adair! LS,! Nelson! MC,! et! al.! FiveKyear! obesity! incidence! in! the! transition! period! between! adolescence! and! adulthood:! The! National! Longitudinal! Study!of!Adolescent!Health.!Am!J!Clin!Nutr!2004;80:569–75.!

[29]! Barlow! SE.! Expert! committee! recommendations! regarding! the! prevention,! assessment,!and!treatment!of!child!and!adolescent!overweight!and!obesity:!summary! report.!Pediatrics!2007;120:S164–92.!

[30]! Krebs! NF,! Jacobson! MS.! Prevention! of! pediatric! overweight! and! obesity.! Pediatrics! 2003;112:424–30.!

[31]! Janssen!I,!Leblanc!AG.!Systematic!review!of!the!health!benefits!of!physical!activity!and! fitness!in!schoolKaged!children!and!youth.!Int!J!Behav!Nutr!Phys!Act!2010;7:40.!

[32]! Hooper! L,! Abdelhamid! A,! Bunn! D,! et! al.! Effects! of! total! fat! intake! on! body! weight.! Cochrane!Database!Syst!Rev!2015:CD011834.!

[33]! Malik!VS,!Schulze!MB,!Hu!FB.!Intake!of!sugarKsweetened!beverages!and!weight!gain:!a! systematic!review.!Am!J!Clin!Nutr!2006;84:274–88.!

[34]! Biddle! SJH,! García! Bengoechea! E,! Wiesner! G.! Sedentary! behaviour! and! adiposity! in! youth:!a!systematic!review!of!reviews!and!analysis!of!causality.!Int!J!Behav!Nutr!Phys! Act!2017;14:43.!

[35]! Davison! KK,! Birch! LL.! Childhood! overweight:! a! contextual! model! and! recommendations!for!future!research.!Obes!Rev!2001;2:159–71.!

[36]! Jokela! M,! Hintsanen! M,! Hakulinen! C,! et! al.! Association! of! personality! with! the! development! and! persistence! of! obesity:! A! metaKanalysis! based! on! individualK participant!data.!Obes!Rev!2013;14:315–23.!

[37]! Gerlach!G,!Herpertz!S,!Loeber!S.!Personality!traits!and!obesity:!a!systematic!review.! Obes!Rev!2015;16:32–63.!

[38]! Luppino! FS,! de! Wit! LM,! Bouvy! PF,! et! al.! Overweight,! obesity,! and! depression:! a! systematic! review! and! metaKanalysis! of! longitudinal! studies.! Arch! Gen! Psychiatry! 2010;67:220–9.! [39]! Vamosi!M,!Heitmann!BL,!Kyvik!KO.!The!relation!between!an!adverse!psychological!and! social!environment!in!childhood!and!the!development!of!adult!obesity:!a!systematic! literature!review.!Obes!Rev!2010;11:177–84.! [40]! Korczak!DJ,!Lipman!E,!Morrison!K,!et!al.!Are!children!and!adolescents!with!psychiatric! illness!at!risk!for!increased!future!body!weight?!A!systematic!review.!Dev!Med!Child! Neurol!2013;55:980–7.! [41]! Mannan!M,!Mamun!A,!Doi!S,!et!al.!Prospective!associations!between!depression!and! obesity!for!adolescent!males!and!females!K!a!systematic!review!and!metaKanalysis!of! longitudinal!studies.!PLoS!One!2016;11.!

[42]! Mühlig! Y,! Antel! J,! Föcker! M,! et! al.! Are! bidirectional! associations! of! obesity! and! depression!already!apparent!in!childhood!and!adolescence!as!based!on!highKquality! studies?!A!systematic!review.!Obes!Rev!2016;17:235–49.!

[43]! Shrewsbury! V,! Wardle! J.! Socioeconomic! status! and! adiposity! in! childhood:! a! systematic!review!of!crossKsectional!studies!1990–2005.!Obesity!2008;16:275–84.! [44]! Slopen!N,!Goodman!E,!Koenen!KC,!et!al.!Socioeconomic!and!other!social!stressors!and! biomarkers!of!cardiometabolic!risk!in!youth:!a!systematic!review!of!less!studied!risk! factors.!PLoS!One!2013;8:e64418.! [45]! Drewnowski!A,!Specter!S.!Poverty!and!obesity:!the!role!of!energy!density!and!energy! costs.!Am!J!Clin!Nutr!2004;79:6–16.!

[46]! de! Vriendt! T,! Moreno! LA,! de! Henauw! S.! Chronic! stress! and! obesity! in! adolescents:! scientific! evidence! and! methodological! issues! for! epidemiological! research.! Nutr! Metab!Cardiovasc!Dis!2009;19:511–9.!

[47]! Gundersen! C,! Mahatmya! D,! Garasky! S,! et! al.! Linking! psychosocial! stressors! and! childhood!obesity.!Obes!Rev!2011;12:e54–63.!

[48]! Pervanidou!P,!Chrousos!GP.!Stress!and!obesity/metabolic!syndrome!in!childhood!and! adolescence.!Int!J!Pediatr!Obes!2011;6:21–8.!

[49]! Shonkoff! JP,! Boyce! WT,! McEwen! BS.! Neuroscience,! molecular! biology,! and! the! childhood!roots!of!health!disparities.!JAMA!2009;301:2252.!

[50]! Evans!GW.!The!environment!of!childhood!poverty.!Am!Psychol!2004;59:77–92.!

[51]! Dallman! MF.! StressKinduced! obesity! and! the! emotional! nervous! system.! Trends! Endocrinol!Metab!2010;21:159–65.!

[52]! Adam!TC,!Epel!ES.!Stress,!eating!and!the!reward!system.!Physiol!Behav!2007;91:449– 58.!

Rev!2001;2:73–86.!

[54]! Torres! SJ,! Nowson! CA.! Relationship! between! stress,! eating! behavior,! and! obesity.! Nutrition!2007;23:887–94.!

[55]! Danese!A,!McEwen!BS.!Adverse!childhood!experiences,!allostasis,!allostatic!load,!and! ageKrelated!disease.!Physiol!Behav!2012;106:29–39.!

[56]! Kessler! RC,! McLaughlin! KA,! Green! JG,! et! al.! Childhood! adversities! and! adult! psychopathology! in! the! WHO! world! mental! health! surveys.! Br! J! Psychiatry! 2010;197:378–85.!

[57]! Hyman!SE.!How!adversity!gets!under!the!skin.!Nat!Neurosci!2009;12:241–3.!

[58]! Felitti! VJ,! Anda! RF,! Nordenberg! D,! et! al.! Relationship! of! childhood! abuse! and! household! dysfunction! to! many! of! the! leading! causes! of! death! in! adults.! Am! J! Prev! Med!1998;14:245–58.! [59]! Bellis!MA,!Lowey!H,!Leckenby!N,!et!al.!Adverse!childhood!experiences:!retrospective! study!to!determine!their!impact!on!adult!health!behaviours!and!health!outcomes!in!a! UK!population.!J!Public!Heal!2014;36:81–91.! [60]! Dong!M,!Anda!RF,!Felitti!VJ,!et!al.!The!interrelatedness!of!multiple!forms!of!childhood! abuse,!neglect,!and!household!dysfunction.!Child!Abus!Negl!2004;28:771–84.! [61]! Anda!RF,!Butchart!A,!Felitti!VJ,!et!al.!Building!a!framework!for!global!surveillance!of! the! public! health! implications! of! adverse! childhood! experiences.! Am! J! Prev! Med! 2010;39:93–8.!

[62]! Schilling! EA,! Aseltine! RH,! Gore! S.! The! impact! of! cumulative! childhood! adversity! on! young! adult! mental! health:! Measures,! models,! and! interpretations.! Soc! Sci! Med! 2008;66:1140–51.!

[63]! Benjet! C,! Borges! G,! MedinaKMora! ME.! Chronic! childhood! adversity! and! onset! of! psychopathology! during! three! life! stages:! childhood,! adolescence! and! adulthood.! J! Psychiatr!Res!2010;44:732–40.!

[64]! Spinhoven!P,!Elzinga!BM,!Hovens!JGFM,!et!al.!The!specificity!of!childhood!adversities! and! negative! life! events! across! the! life! span! to! anxiety! and! depressive! disorders.! J! Affect!Disord!2010;126:103–12.!

[65]! Danese!A,!Tan!M.!Childhood!maltreatment!and!obesity:!systematic!review!and!metaK analysis.!Mol!Psychiatry!2013;19:544–54.!

[66]! Hemmingsson! E,! Johansson! K,! Reynisdottir! S.! Effects! of! childhood! abuse! on! adult! obesity:!a!systematic!review!and!metaKanalysis.!Obes!Rev!2014;15:882–93.!

[67]! Michels!N,!Sioen!I,!Boone!L,!et!al.!CrossKlagged!associations!between!children’s!stress! and!adiposity.!Psychosom!Med!2014;77:50–8.!

[68]! Francis! MM,! Nikulina! V,! Widom! CS.! A! prospective! examination! of! the! mechanisms! linking! childhood! physical! abuse! to! body! mass! index! in! adulthood.! Child! Maltreat! 2015;20:203–13.!

[69]! van!Reedt!Dortland!AKB,!Giltay!EJ,!van!Veen!T,!et!al.!Personality!traits!and!childhood! trauma!as!correlates!of!metabolic!risk!factors:!The!Netherlands!Study!of!Depression! and! Anxiety! (NESDA).! Prog! NeuroKPsychopharmacology! Biol! Psychiatry! 2012;36:85– 91.!

[70]! Ferguson!E,!Matthews!G,!Cox!T.!The!Appraisal!of!Life!Events!(ALE)!scale:!reliability!and! validity.!Br!J!Health!Psychol!1999;4:97–116.!

[71]! Vinkers! CH,! Joëls! M,! Milaneschi! Y,! et! al.! Stress! exposure! across! the! life! span! cumulatively! increases! depression! risk! and! is! moderated! by! neuroticism.! Depress! Anxiety!2014;31:737–45.!

[72]! Hemmingsson!E.!A!new!model!of!the!role!of!psychological!and!emotional!distress!in! promoting!obesity:!conceptual!review!with!implications!for!treatment!and!prevention.! Obes!Rev!2014;15:769–779.!

[73]! Infurna! MR,! Reichl! C,! Parzer! P,! et! al.! Associations! between! depression! and! specific! childhood! experiences! of! abuse! and! neglect:! a! metaKanalysis.! J! Affect! Disord! 2016;190:47–55.!

[74]! Lindert!J,!von!Ehrenstein!OS,!Grashow!R,!et!al.!Sexual!and!physical!abuse!in!childhood! is!associated!with!depression!and!anxiety!over!the!life!course:!systematic!review!and! metaKanalysis.!Int!J!Public!Health!2014;59:359–72.!

[75]! Norman! RE,! Byambaa! M,! De! R,! et! al.! The! longKterm! health! consequences! of! child! physical!abuse,!emotional!abuse,!and!neglect:!a!systematic!review!and!metaKanalysis.! PLoS!Med!2012;9:e1001349.!

[76]! Li!M,!D’Arcy!C,!Meng!X.!Maltreatment!in!childhood!substantially!increases!the!risk!of! adult!depression!and!anxiety!in!prospective!cohort!studies:!systematic!review,!metaK analysis,!and!proportional!attributable!fractions.!Psychol!Med!2016;46:717–30.!

[77]! Roberts! RE,! Duong! HT.! Do! anxiety! disorders! play! a! role! in! adolescent! obesity?! Ann! Behav!Med!2016;50:613–21.!

[78]! Anderson! SE,! Cohen! P,! Naumova! EN,! et! al.! Association! of! depression! and! anxiety! disorders! with! weight! change! in! a! prospective! communityKbased! study! of! children! followed!up!into!adulthood.!Arch!Pediatr!Adolesc!Med!2006;160:285–91.! [79]! Oldehinkel!AJ,!Ormel!J.!A!longitudinal!perspective!on!childhood!adversities!and!onset! risk!of!various!psychiatric!disorders.!Eur!Child!Adolesc!Psychiatry!2015;24:641–50.! [80]! Oldehinkel!AJ,!Bouma!EMC.!Sensitivity!to!the!depressogenic!effect!of!stress!and!HPAK axis!reactivity!in!adolescence:!A!review!of!gender!differences.!Neurosci!Biobehav!Rev! 2011;35:1757–70.! [81]! Terracciano!A,!Sutin!AR,!McCrae!RR,!et!al.!Facets!of!personality!linked!to!underweight! and!overweight.!Psychosom!Med!2009;71:682–9.! [82]! Kim!J.!Personality!traits!and!body!weight:!evidence!using!sibling!comparisons.!Soc!Sci! Med!2016;163:54–62.!

[83]! Sutin! AR,! Terracciano! A.! Personality! traits! and! body! mass! index:! modifiers! and! mechanisms.!Psychol!Health!2016;31:259–75.!

[84]! Oldehinkel! AJ,! Rosmalen! JG,! Buitelaar! JK,! et! al.! Cohort! profile! update:! the! TRacking! Adolescents’!Individual!Lives!Survey!(TRAILS).!Int!J!Epidemiol!2015;44:76–76n.!

[85]! Huisman! M,! Oldehinkel! AJ,! de! Winter! A,! et! al.! Cohort! profile:! the! Dutch! “TRacking! Adolescents”!Individual!Lives’!Survey’;!TRAILS.!Int!J!Epidemiol!2008;37:1227–35.! [86]! World!Health!Organization!(WHO).!Obesity!and!overweight!K!fact!sheet.!Available!at:!

[87]! Centers!for!Disease!Control!and!Prevention!(CDC).!Body!Mass!Index!(BMI).!Available! at:!https://www.cdc.gov/healthyweight/assessing/bmi/index.html.!

[88]! Penninx!BW,!Milaneschi!Y,!Lamers!F,!et!al.!Understanding!the!somatic!consequences! of! depression:! biological! mechanisms! and! the! role! of! depression! symptom! profile.! BMC!Med!2013;11:129.!

[89]! Gariepy!G,!Nitka!D,!Schmitz!N.!The!association!between!obesity!and!anxiety!disorders! in!the!population:!a!systematic!review!and!metaKanalysis.!Int!J!Obes!2010;34:407–19.