bullied children and psychosomatic problems: a meta...

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Bullied Children and Psychosomatic Problems: A Meta-analysis abstract BACKGROUND AND OBJECTIVE: A previous meta-analysis showed that being bullied during childhood is related to psychosomatic problems, but many other studies have been published since then, including some longitudinal studies. We performed a new meta-analysis to quantify the association between peer victimization and psychosomatic complaints in the school-aged population. METHODS: We searched online databases up to April 2012, and bibliog- raphies of retrieved studies and of narrative reviews, for studies that examined the association between being bullied and psychosomatic complaints in children and adolescents. The original search identied 119 nonduplicated studies, of which 30 satised the prestated inclusion criteria. RESULTS: Two separate random effects meta-analyses were performed on 6 longitudinal studies (odds ratio = 2.39, 95% condence interval, 1.76 to 3.24) and 24 cross-sectional studies (odds ratio = 2.17, 95% condence interval, 1.91 to 2.46), respectively. Results showed that bullied children and adolescents have a signicantly higher risk for psychosomatic problems than non-bullied agemates. In the cross- sectional studies, the magnitude of effect size signicantly decreased with the increase of the proportion of female participants in the study sample. No other moderators were statistically signi cant. CONCLUSIONS: The association between being bullied and psychoso- matic problems was conrmed. Given that school bullying is a wide- spread phenomenon in many countries around the world, the present results indicate that bullying should be considered a signicant inter- national public health problem. Pediatrics 2013;132:720729 AUTHORS: Gianluca Gini, PhD, and Tiziana Pozzoli, PhD Department of Developmental and Social Psychology, University of Padua, Padua, Italy KEY WORDS bullying, peer victimization, psychosomatic problems, health, meta-analysis ABBREVIATIONS CIcondence interval N fs fail-safe N ORodds ratio SESsocioeconomic status Dr Gini contributed to protocol design, literature search, data extraction, statistical analysis, and writing the manuscript; Dr Pozzoli contributed to literature search, data extraction, and writing the manuscript; and both authors approved the nal manuscript as submitted. www.pediatrics.org/cgi/doi/10.1542/peds.2013-0614 doi:10.1542/peds.2013-0614 Accepted for publication Jul 10, 2013 Address correspondence to Gianluca Gini, PhD, Department of Developmental and Social Psychology, via Venezia 8, 35131, Padova, Italy. E-mail: [email protected] PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275). Copyright © 2013 by the American Academy of Pediatrics FINANCIAL DISCLOSURE: The authors have indicated they have no nancial relationships relevant to this article to disclose. FUNDING: No external funding. POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conicts of interest to disclose. 720 GINI and POZZOLI by guest on June 11, 2018 www.aappublications.org/news Downloaded from

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  • Bullied Children and Psychosomatic Problems:A Meta-analysis

    abstractBACKGROUND AND OBJECTIVE: A previous meta-analysis showed thatbeing bullied during childhood is related to psychosomatic problems,but many other studies have been published since then, including somelongitudinal studies. We performed a new meta-analysis to quantify theassociation between peer victimization and psychosomatic complaints inthe school-aged population.

    METHODS: We searched online databases up to April 2012, and bibliog-raphies of retrieved studies and of narrative reviews, for studies thatexamined the association between being bullied and psychosomaticcomplaints in children and adolescents. The original search identified119 nonduplicated studies, of which 30 satisfied the prestated inclusioncriteria.

    RESULTS: Two separate random effects meta-analyses were performedon 6 longitudinal studies (odds ratio = 2.39, 95% confidence interval,1.76 to 3.24) and 24 cross-sectional studies (odds ratio = 2.17, 95%confidence interval, 1.91 to 2.46), respectively. Results showed thatbullied children and adolescents have a significantly higher risk forpsychosomatic problems than non-bullied agemates. In the cross-sectional studies, the magnitude of effect size significantly decreasedwith the increase of the proportion of female participants in the studysample. No other moderators were statistically significant.

    CONCLUSIONS: The association between being bullied and psychoso-matic problems was confirmed. Given that school bullying is a wide-spread phenomenon in many countries around the world, the presentresults indicate that bullying should be considered a significant inter-national public health problem. Pediatrics 2013;132:720729

    AUTHORS: Gianluca Gini, PhD, and Tiziana Pozzoli, PhD

    Department of Developmental and Social Psychology, Universityof Padua, Padua, Italy

    KEY WORDSbullying, peer victimization, psychosomatic problems, health,meta-analysis

    ABBREVIATIONSCIconfidence intervalNfsfail-safe NORodds ratioSESsocioeconomic status

    Dr Gini contributed to protocol design, literature search, dataextraction, statistical analysis, and writing the manuscript; DrPozzoli contributed to literature search, data extraction, andwriting the manuscript; and both authors approved the finalmanuscript as submitted.

    www.pediatrics.org/cgi/doi/10.1542/peds.2013-0614

    doi:10.1542/peds.2013-0614

    Accepted for publication Jul 10, 2013

    Address correspondence to Gianluca Gini, PhD, Department ofDevelopmental and Social Psychology, via Venezia 8, 35131,Padova, Italy. E-mail: [email protected]

    PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).

    Copyright 2013 by the American Academy of Pediatrics

    FINANCIAL DISCLOSURE: The authors have indicated they haveno financial relationships relevant to this article to disclose.

    FUNDING: No external funding.

    POTENTIAL CONFLICT OF INTEREST: The authors have indicatedthey have no potential conflicts of interest to disclose.

    720 GINI and POZZOLI by guest on June 11, 2018www.aappublications.org/newsDownloaded from

    mailto:[email protected]

  • Being bullied during childhood or ad-olescence is a risk factor for a personswell-being and adjustment. Studieshave shown that peer victimization isrelated mainly to internalizing prob-lems, including low self-esteem, highanxiety, and depression,14 and it alsois linked to suicidal ideation and at-tempt.5,6 Moreover, it is increasinglyrecognized that bullied students canalso be affected by poor physical healthand show a variety of symptoms, suchas headache, backache, abdominal pain,skin problems, sleeping problems, bed-wetting, or dizziness.711 Given that insuch circumstances psychosocial pro-cesses seem to act as a key factor neg-atively affecting childrens health, thesesymptoms are often called psychoso-matic problems.710

    To date, the only meta-analysis12 spe-cifically conducted on this issue waspublished in 2009. That meta-analysissynthesized the results of 11 studiesthat have analyzed the association be-tween being victimized by peers atschool and the prevalence of symp-toms among children and adolescentsbetween 7 years and 16 years of age.Bullied students were found to havea significantly higher risk for psycho-somatic problems than were the con-trols, that is, the agemates who werenot involved in bullying (pooled oddsratio [OR] = 2.00, 95% confidence in-terval [CI], 1.70 to 2.35). Although im-portant, those results were limited bythe small number of studies includedin the meta-analysis (which also pre-cluded the possibility of testing forpossible moderators), and the resultswere also limited by the fact that only 2of them used a longitudinal design.

    Subsequently, another meta-analysis3

    has analyzed data from longitudinalstudies that measured a variety ofinternalizing problems, including psy-chosomatic symptoms. Overall, thismeta-analysis has confirmed that peervictimization is positively associated

    with poor well-being. However, Reijntjesand colleagues review included only 2studies that measured psychosomaticsymptoms; unfortunately, these symp-toms were not distinguished from othertypes of internalizing problems (eg, de-pression, anxiety, or loneliness), but apooled correlation for each study wascomputed, with no comparison betweenbullied and nonbullied children.

    Since the publication of the first meta-analysis in 2009, several other studiesthat assessed the risk for psychoso-matic problems in bullied children havebeen added to the literature, includingsome studies that used a longitudinaldesign. This new meta-analysis seeksto update and expand both Gini andPozzolis and Reijntjes and colleaguesmeta-analyses3,12 by (1) including thesubsequently published studies thatallowed to estimate the risk for psy-chosomatic problems in children andadolescents who are bullied by peers(ie, cases) compared with nonbulliedpeers (ie, controls), (2) performingseparate meta-analyses of longitudinaland cross-sectional studies, and (3)testing for potential moderators of vari-ation in the magnitude of effect sizes.

    METHODS

    Literature Search

    Four methods were used to identify rel-evant studies. First, electronic searchesin PsycINFO, PubMed, the Cochrane Li-brary database, the Campbell Collabo-ration database, and Scopus wereconducted inApril 2012with the followingkeywords: bullying, peer victimiza-tion AND somatic, psychosomatic,and physical health. Second, the citedby function in Scopus was used to re-trieve empirical articles that have citedthe previous meta-analysis.12 Third, re-view articles about consequences ofbullying were reviewed for possible rel-evant citations. Finally, the referencesections of the collected articles weresearched for relevant earlier references.

    This meta-analysis was planned, con-ducted, and reported in adherence tothe Meta-analysis of Observational Stud-ies in Epidemiology guidelines.13

    Inclusion Criteria

    A study had to meet the followingapriori criteria tobe included. Themostbasic requirement was the inclusionof measures of peer victimization atschool in childhood or adolescence andof psychosomatic symptoms. Thesemeasures could include self-reportquestionnaires; peer, parent, or teacherreports; or an interview that resultedin a quantitative rating of peer victimi-zation and health problems. Second,studieswere required to have reportedeffect sizes and related confidenceintervals or enough information to cal-culate these data, for example, by re-porting comparisons between bulliedchildren and a control group (definedas children from thesamepopulationofvictims who were classified as notbullied). We excluded the followingtypes of studies: studies that did notinclude a control group; studies thatmeasured psychosomatic symptomswith items included in a larger scale,because these symptoms could not beclearly distinguished from other prob-lems; studies with duplicated data;studies that did not report analyses onthe variables of interest; and studieswith adults or psychiatric patients. Theauthors independentlyassessedwhetherarticlesmet the inclusioncriteria. In thecase of disagreement, a consensuswasreached through discussion.

    Coding of Studies

    Studies were coded on design (cross-sectional versus longitudinal), lengthof follow-up for longitudinal studies, typeof bullying measure (self-report ques-tionnaire versus peer or adult reportsversus interview), typeofpsychosomaticsymptoms measured, type of samplingprocedure, sample composition and char-acteristics, and geographic location of

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  • study. Quantitative data were extractedfrom text and tables; for the sake ofcomparability with the results of theformer meta-analysis,12 the data thatwere adjusted for important con-founders (eg, gender, age, ethnicity, orparental education) were preferred.

    Statistical Analyses

    Eleven studies reported an effect basedon a single composite score for psy-chosomatic complaints, whereas theremaining studies reported data fora number of different symptoms dis-tinctly (eg, headache, stomachache,backache, abdominal pain, dizziness,sleeping problems, poor appetite, bed-wetting, skin problems, vomiting; seeTable 1). Because the number and thetype of symptoms varied systemati-cally across studies, following Gini andPozzolis original procedure,12 the ORfor each symptom was extracted, andthen a pooled OR was computed fromeach study. (Items that referred topsychological problems, such as anxi-ety or depression, were not included inthis computation.) This procedureallowed a direct comparison with theresults of the former meta-analysis.The case group included victims, thatis, children who are bullied by peers.The control group featured childrenwho have not been bullied. With veryfew exceptions, studies did not reportresults for boys and girls separately;therefore, we were not able to compareeffect sizes for these two groups ofchildren. Because most of the studiesreported the proportion of girls in thesample, we used this information totest for possible moderation by gender.

    Analyses were done using Compre-hensive Meta-Analysis.14 We extractedthe OR and 95% CI from each study. Datafrom individual studies were pooled byusing a random effects model. Eachstudy was weighted by the inverse of itsvariance, which, under the random ef-fects model, includes the within-study

    variance plus the between-studiesvariance t-squared (2). The z statis-tic was calculated, and a two-tailedP value of ,.05 was considered to in-dicate statistical significance. Statisti-cal heterogeneity was assessed byusing the Q statistic to evaluatewhether the pooled studies representa homogeneous distribution of effectsizes. Also reported is the I2 statistic,indicating the proportion of observedvariance that reflects real differencesin effect size.15

    Toaddress thepossiblepublicationbias(ie, the fact that studies with non-significant results are less likely to bepublished), we computed the fail-safe N(Nfs) according to the method Orwin16

    proposed, which is more conservativethan the traditional Rosenthal Nfs.17,18

    Orwins Nfs determines the number ofadditional studies in a meta-analysisyielding null effect sizes that wouldbe needed to yield a trivial OR of1.05. Researchers suggest that meta-analysts calculate a tolerance levelaround a fail-safe N that is equal to 5times the number of effects included inthemeta-analysis plus 10 (the 5k + 10benchmark).18,19 Moreover, the associ-ation between the standardized effectsizes and the variances of these effectswas analyzed by rank correlation withuse of the Kendall t method. If smallstudies with negative results were lesslikely to be published, the correlationbetween variance and effect size wouldbe high. Conversely, a lack of a signifi-cant correlation can be interpreted asthe absence of publication bias.20

    RESULTS

    After the removal of duplicates, a list of119 potentially eligible studies wasgenerated (Fig 1). Based on titles andabstracts, 55 articles were excluded atthe first screening because they werequalitative studies, reviews or commen-taries, or studies that did not measureschool bullying. Full-text copies of the

    remaining 64 potentially relevant stud-ies were obtained. Fourteen studieswere excluded because they did notmeet the inclusion criteria (eg, they didnot have a control group). Fifteen stud-ies did not report enough data to com-pute effect sizes or confidence intervals.Five studies were not available in fulltext. The remaining 30 studies were in-cluded for this meta-analysis. Six stud-ies were longitudinal studies, and 24used a cross-sectional design.

    Table 1 summarizes the characteristicsof the studies included in this meta-analysis, including sample size andresponse rate, age and gender com-position of the sample, type of mea-sures, symptomsmeasured, studydesign,and type of sampling. A total of 219 560children and adolescents participatedin the 30 studies. Across the 26 studiesthat provided information about thesamples gender composition, 50.2%(range, 32.8% to 62.4%) of the partic-ipants were girls.

    Five studies were from Norway, 2 ofwhich were from the same publi-cation28,34,35,38; 4 from the UnitedStates22,23,27,43; 3 from Australia8,11,37; 2from the United Kingdom44,45; 2 from theNetherlands7,25; 2 from Finland31,36; 2from India33,40; and 1, respectively, fromAustria,26 China,29 France,30 Germany,41

    Greenland,42 Italy,10 Mexico,21 and Tur-key.32 Two articles reported data frommultiple countries.24,39 Information aboutrace or ethnicity and socioeconomicstatus (SES) of the participants was notsystematically reported in all studies.Overall, the heterogeneity of racial andSES classification within and across thestudies was such that it precluded anal-ysis by race and ethnicity or SES.

    Meta-analysis of LongitudinalStudies

    Six studies used a longitudinal design.The follow-up duration ranged from 9months to 11 years. Across the 6 sam-ples, bullied children were found to

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  • TABLE1

    Characteristicsof

    StudiesIncluded

    intheMeta-analysis

    Source

    SampleSize

    (responserate)

    AgeRange,

    y(%

    girls)

    BullyingMeasure

    Symptom

    Measure

    Symptom

    sReported

    Adjustmentfor

    Confounders

    StudyDesign

    Type

    ofSampling

    Albores-Gallo

    etal(2011)

    21340(n/a)

    711

    (n/a)

    Peer

    nomination

    questionnaire

    Self-report

    questionnaire

    Singlescore

    None

    Cross-sectional

    Convenience

    sample

    Biebletal(2011)22

    65(n/a)

    1220

    attim

    e3(52.9)

    Time1:play

    session;

    time3:self-report

    questionnaire

    Self-report

    questionnaire

    Singlescore

    Gender

    Longitudinal

    Convenience

    sample

    Burk

    etal(2011)

    23344(60%

    )715

    (52.3)

    Multi-inform

    ant(self-,

    teacher-,parent

    report)

    Multi-inform

    ant

    (self-,teacher-,

    parent

    report)

    Singlescore

    None

    Longitudinal

    Convenience

    sample

    Dueetal(2005)

    24123227(.

    90%)

    1115

    (51)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache,stomachache,

    backache,sleeping

    difficulties,tired

    inthe

    morning,dizziness,

    irritable,feelingnervous

    Age,family

    affluence,

    country

    Cross-sectional

    Clusterrandom

    sampling

    Fekkes

    etal(2004)

    72766

    (100%)

    912

    (50)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache,skinproblems,

    abdominalpain,tense

    muscles,feelingtired,

    badappetite

    Gender

    Cross-sectional

    Unknow

    n

    Fekkes

    etal(2006)

    251118

    (70%

    )911

    (50.3)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Abdominalpain,sleeping

    problems,headache,

    feelingtense,feelingtired,

    poor

    appetite,bedw

    etting

    Gender,age,having

    friends

    Longitudinal

    Unknow

    n

    Forero

    etal(1999)

    83918

    (86%

    )1115

    (54.3)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Singlescore

    Clusters

    within

    schools

    Cross-sectional

    Clusterrandom

    sampling

    Gini(2008)

    10565(94%

    )811

    (52.9)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache,abdom

    inalpain,

    feelingtired,feelingtense,

    sleeping

    problems,

    dizziness

    Gender,age

    Cross-sectional

    Simplerandom

    sampling

    Gradinger

    etal(2009)

    26761(95%

    )1419

    (51.5)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Singlescore

    None

    Cross-sectional

    Convenience

    sample

    Gruber

    andFineran

    (2008)

    27522(51%

    )1217

    (42.9)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Singlescore

    None

    Cross-sectional

    Convenience

    sample

    Haavetetal(2004)

    288316

    (88%

    )15

    (54.4)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache,painfrom

    neck

    orshoulder

    None

    Cross-sectional

    Populationstudy

    Heskethetal

    (2010)

    292191

    (80%

    )912

    (44)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache,abdom

    inalpain

    Gender,age,residence,

    parentaleducation

    Cross-sectional

    Simplerandom

    sampling

    Houbre

    etal(2006)

    30291(95%

    )912

    (n/a)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Skinconditions,sleeping

    disorders,digestive

    disorders,somaticpain,

    vegetativesymptom

    s,diarrhea,and

    constipation

    None

    Cross-sectional

    Convenience

    sample

    Kaltiala-Heino

    etal(2000)

    3117

    643(87%

    )1416

    (49.3)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Singlescore

    Age,gender,fam

    ilystructure,parental

    education

    Cross-sectional

    Convenience

    sample

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  • TABLE1

    Continued

    Source

    SampleSize

    (responserate)

    AgeRange,

    y(%

    girls)

    BullyingMeasure

    Symptom

    Measure

    Symptom

    sReported

    Adjustmentfor

    Confounders

    StudyDesign

    Type

    ofSampling

    Karatasand

    Ozturk

    (2011)

    3292

    (82%

    )1012

    (51.1)

    Self-report

    questionnaire

    Parent

    report

    questionnaire

    Headache,abdom

    inalpain,

    stom

    achache,backache,

    skinproblems,restlessness,

    nervousness,sleeping

    problems,dizziness,

    respiratoryproblems,poor

    appetite

    None

    Cross-sectional

    Simplerandom

    sampling

    Kshirsagar

    etal(2007)

    33500(100%)

    812

    (62.4)

    Semistructured

    interview

    Semistructured

    interview

    Headache,tum

    myaches,

    body

    ache,has

    failed,bites

    nails,sleep

    problems,

    vomiting,bedwetting

    Notspecified

    Longitudinal

    Simplerandom

    sampling

    Lien

    etal(2009)

    (sam

    ple1)

    343790

    (88%

    )1516

    (49.3)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache;paininneck

    orshoulder;paininarm,

    leg,or

    knee;abdom

    inal

    pain;backpain

    SES,family

    structure,

    ethnicity,exposure

    toviolence,having

    closefriends

    Cross-sectional

    Populationstudy

    Lien

    etal(2009)

    (sam

    ple2)

    343790

    (80%

    )1819

    (55.9)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache;paininneck

    orshoulder;paininarm,

    leg,or

    knee;abdom

    inal

    pain;backpain

    SES,family

    structure,

    ethnicity,exposureto

    violence,havingclose

    friends

    Cross-sectional

    Populationstudy

    Lhreetal(2011)

    35419(100%)

    716

    (n/a)

    Multi-inform

    ant

    (self-,teacher-,

    parent

    report)

    Self-report

    questionnaire

    Stom

    achache,headache

    Gender,grade

    Cross-sectional

    Convenience

    sample

    Luntam

    oetal(2012)

    362215

    (91%

    )1318

    (50)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache,abdom

    inalpain,

    sleepproblems

    None

    Cross-sectional

    Populationstudy

    McGee

    etal(2011)

    371806

    (n/a)

    1421

    (51.8)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Singlescore

    Childhood

    aggression,

    socialor

    thought

    problembehaviors,

    poverty,physical

    punishment

    Longitudinal

    Populationstudy

    Natvigetal(2001)

    38856(83.7%

    )1315

    (50.6)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache,stomachache,

    backache,feelingdizzy,

    irritability,feelingnervous,

    sleeplessness

    Gender,age,school

    Cross-sectional

    Unknow

    n

    Nordhagen

    etal(2005)

    3917

    114(68%

    )217

    (49.1)

    Parent

    report

    questionnaire

    Parent

    report

    questionnaire

    Singlescore

    Gender,age,country,

    livingarea,fam

    ilysituation,education

    Cross-sectional

    Stratified

    random

    sampling

    Ramya

    andKulkarni

    (2011)

    40500(n/a)

    814

    (32.8)

    Interview

    Interview

    Headache,tum

    myache,

    bedw

    etting,fever

    None

    Cross-sectional

    Simplerandom

    sampling

    Richteretal

    (2007)

    415650

    (70%

    80%)

    1115

    (49.8)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Singlescore

    None

    Cross-sectional

    Clusterrandom

    sampling

    Rigby(1999)

    1178

    (28.3%

    )Time1:13.8,

    Time2:16.7(44.9)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Singlescore

    None

    Longitudinal

    Convenience

    sample

    Schnohrand

    Niclasen

    (2006)

    42891(n/a)

    1115

    (n/a)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache,stomachache,

    sleeping

    difficulties

    Gender,age

    Cross-sectional

    Clusterrandom

    sampling

    724 GINI and POZZOLI by guest on June 11, 2018www.aappublications.org/newsDownloaded from

  • have a significantly higher risk forpsychosomatic problems than non-bullied agemates were (OR = 2.39, 95%CI, 1.76 to 3.24, Z = 5.62, P , .0001).Figure 2 shows the forest plot for thismeta-analysis. Studies were highly ho-mogeneous (Q = 4.94, P = .42, I2 = 0%).Furthermore, no evidence of publica-tion bias was present. Kendalls t was.53 with two-tailed P = .13. An additional102 studies with null effect sizes wouldbe needed to attenuate this omnibus

    effect size to a trivial effect (5k + 10benchmark = 40).

    Meta-analysis of Cross-SectionalStudies

    Across the 24 samples that were in-cluded in the cross-sectional studies,bullied children were found to havea significantly higher risk for psycho-somatic problems than were non-bullied peers (OR = 2.17, 95% CI, 1.91 to2.46, Z = 12.09, P , .0001). Figure 3

    TABLE1

    Continued

    Source

    SampleSize

    (responserate)

    AgeRange,

    y(%

    girls)

    BullyingMeasure

    Symptom

    Measure

    Symptom

    sReported

    Adjustmentfor

    Confounders

    StudyDesign

    Type

    ofSampling

    Srabsteinetal

    (2006)

    4315

    305(83%

    )1115

    (53.5)

    Self-report

    questionnaire

    Self-report

    questionnaire

    Headache,stomachache,

    dizziness,backache,

    irritability,feelingnervous,

    sleeping

    problems

    Gender,age,race,

    overweight,maternal

    education

    Cross-sectional

    Clusterrandom

    sampling

    Williamsetal

    (1996)

    442962

    (93.1%

    )710

    (n/a)

    Semistructured

    interview

    Semistructured

    interview

    Sleeping

    problems,bed

    wetting,headache,

    tummyache

    Notspecified

    Cross-sectional

    Populationstudy

    Wolke

    etal(2001)

    451639

    (82%

    )69(49.6)

    Interview

    Parent

    report

    questionnaire

    Sore

    throat,coldor

    coughs,

    breathingproblems,

    nausea,poorappetite

    Gender,schoolyear,

    ethnicminority

    Cross-sectional

    Convenience

    sample

    n/a,notavailable.

    FIGURE 1Flow diagram of study inclusion.

    FIGURE 2Forest plot for random effects meta-analysis of the association between being bullied and psycho-somatic problems: longitudinal studies. Note: Effect sizes are expressed as odds ratios. Studies arerepresented by symbols whose area is proportional to the studys weight in the analysis.

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  • shows the forest plot for this meta-analysis. Effect sizes within this groupof studies were not homogeneous (Q =103.06, P , .001, I2 = 77.7%). Again, noevidence of publication bias was pres-ent. Kendalls t was .05 with two-tailedP= .75. An additional 325 studieswith nulleffect sizeswould be needed to attenuatethis omnibus effect size to a negligiblevalue (5k + 10 benchmark = 130).

    Moderator analyses with gender com-position of the sample, geographic lo-cation, and type of informant wereperformed to explore possible explan-ations for heterogeneity in the effectsizes across cross-sectional studies.The proportion of girls in the samplewas available for 20 of the 24 cross-sectional studies, and it was used asa continuous predictor in a weightedmixed-effects metaregression. Themagnitudeof theeffect sizesignificantlydecreased with an increase in thenumber of female participants in thestudy sample (B =20.04, 95% CI,20.07to 20.02, P , .002). The studys geo-graphic location (coded as Europeversus other countries) was not a sig-nificant moderator (k = 15, OR = 2.19,95% CI, 1.82 to 2.62, and k = 8, OR = 2.16,

    95% CI, 1.61 to 2.90, respectively; Q =0.004, P = .95).

    Moreover, thepotentialmoderatingroleof amethodological feature, namely thetype of informant, was tested. Twentystudies used the participant as an in-formant for involvement in bullying (ie,used self-report questionnaires orinterviews with the child), and only 4studies collected data through otherinformants (ie, peers or parents). Effectsizes did not vary as a function of thetype of informant associated with bul-lyingexperiences (OR=2.17,95%CI, 1.86to2.53 for self-reports, OR=2.18, 95%CI,1.55 to 3.06 for other informants; Q =0.00, P = .98). Similarly, 19 studies col-lected information about symptomsfrom the participants themselves (OR =2.21, 95% CI, 1.90 to 2.58), whereas 5studies asked other informants (OR =2.00, 95% CI, 1.47 to 2.72). Also, the ef-fect of this moderator was not statis-tically significant: Q = 0.37, P = .57.

    Finally, as in the formermeta-analysis,12

    a sensitivity analysis was performedbased on the quality of the studies.Quality was assessed through 2 crite-ria (beyond those required as inclusioncriteria): the use of a randomized

    sampling design or a whole populationof students and a good response rate(.80%). Twelve studies satisfied bothcriteria. We then performed a separatemeta-analysis of this subgroup ofstudies, and the results were OR = 2.10,95% CI, 1.87 to 2.46.

    DISCUSSION

    Our meta-analysis showed that bulliedpupils are at least two timesmore likelythan nonbullied agemates to havepsychosomatic problems. Thus, thisupdated meta-analysis confirmed thefindings of the former meta-analyticsynthesis12 with a much larger sampleof studies. Importantly, the same resultwas found not only with cross-sectionalstudies but also in a meta-analysis of 6studies that used a longitudinal design.Finally, the meta-regression analysisshowed that the strength of the re-lationship between being bullied andhaving health problems is higher whensamples contain proportionally moreboys. Given the explorative nature ofthis analysis, a significant finding is notto be considered definitive, but it doessuggest a direction for additional re-search. A possible explanation mightdeal with the fact that a school orclassroom environment with a higherproportion of male students is a con-text in which bullying behavior is morelikely to happen and where supportiveand helping behaviors in favor of thebullied pupils are less frequent.46 Thiscould increase the negative impact ofbeing bullied on childrens health. Theinfluence of the school environmentsgender composition on peer victimiza-tion and its consequences for child-rens well-being is a topic that warrantsadditional research.

    Since the former meta-analysis, thenumber of studies testing the associ-ation between bullying experiences andpsychosomatic problems has tripled.We can reasonably conclude that thisassociation is established, and we call

    FIGURE 3Forest plot for random effects meta-analysis of the association between being bullied and psycho-somatic problems: cross-sectional studies. Note: Effect sizes are expressed as odds ratios. Studies arerepresented by symbols whose area is proportional to the studys weight in the analysis.

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  • for new research efforts aimed atelucidating the mechanisms throughwhich bullying affects childrens health.We also call for research that inves-tigates how other environmental fac-tors interact with peer victimizationexperiences to determine health risk.However, not all children are at thesame risk for developing health prob-lems: Some children may be more re-silient than others against a high-riskenvironment. To explain this adaptivesuccess, protective factors must beconsidered. For example, supportiveparentchild relationships, character-ized by parental warmth, supervision,support, and involvement, may protectchildren from adverse life experiencesat school, such as being bullied bypeers, and thus reduce negative con-sequences. Similarly, attachment toschool, sense of belonging, and schoolsupport may be related to better stu-dent health. Longitudinal studies thataddress the mediating role of theseand other environmental factors on thepeer victimizationhealth problemslink are much needed.

    Strengths and Limitations

    The strengths of this meta-analysis in-clude the much larger number ofstudies that were available this timecompared with the former meta-analysis. Another strength is the widegeographic distribution of the samples,which were derived from several dif-ferent countries around the world.Furthermore, we were able to performseparate meta-analyses of longitudinaland cross-sectional studies, whichyielded the same results. Finally, we didnot find evidence of publication biasthat may have led to overestimating theassociation between bullying and psy-chosomatic problems.

    Meta-analysis is an invaluable tool forintegratingprior research, illuminatingresearch gaps, and defining prioritiesfor future research. However, the fact

    that the major limitations of the liter-ature that were highlighted in the firstmeta-analysis are still present is star-tling to see. Forexample,much variabilityexists in the methods and instrumentsused to assess the prevalence of symp-toms and peer victimization experiences.The majority of studies used a variety ofself-report questionnaires, both for peervictimization and for childrens healthcomplaints. In some cases, these mea-sures were reduced to a single-itemquestionnaire. Self-report measuresare very common in bullying researchand are usually considered to be validand reliable.47 However, possible pro-blems with these instruments are thatthey require a good level of respond-entsself-consciousness and that somebullied children may deny their condi-tion. Finally, associations between dataderived from the same source (ie,when children self-report both bullyingexperiences and health problems)might be inflated by the commonmethod variance. For these reasons,we stress the need for future studies tocollect information through multipleindependent informants, such as chil-dren themselves, their peers within theclass, and their teachers or parents.Moreover, it is important that research-ers choose validated and widely usedinstruments rather than ad hoc or newlydeveloped scales with no evidence ofreliability or validity. Also, the assess-ment of childrens physical health mustbe improved. For example, none of theavailable studies included independentobjective information, such as childrensschool absenteeism extracted fromschool attendance records or their visitsto the school nurse office.

    Furthermore, thestudies includedin thismeta-analysis, and in the former meta-analysis, did not measure differentforms of victimization separately (ie,physical and relational victimization) ordid not report separate analyses fordifferent forms of victimization. Despite

    their overlapping, research has dem-onstrated the importance of dis-tinguishing the 2 forms of victimizationbecause they may be differentially re-lated to personal adjustment.48 Futurestudies should analyze the negativehealth consequences of physical andrelational victimization experiences.

    Finally, our meta-analysis shares thesame limitations of all meta-analyses ofobservational studies. Because indi-viduals cannot be randomlyallocated togroups, the influence of confoundingvariables cannot be fully evaluated.Although many studies controlled forimportant confounding variables, suchas parental education and socioeco-nomic status or exposure to violenceoutside of school, other unknown con-founders could be partially responsiblefor the effect observed.

    Implications for Practitioners

    Thestudiesreviewedsupported the factthat bullied children have more fre-quent psychosomatic problems thannonbullied pupils. Moreover, this meta-analysis significantly complements thegrowing body of research that docu-ments the poor personal adjustment ofbullied children and adolescents, interms of both internalizing and exter-nalizing problems, which other recentmeta-analyses on the psychosocialconsequences of peer victimization3,4,49

    summarize. Altogether, these resultshave significant implications for pedia-tricians, child psychologists, and otherhealth care professionals. It is very im-portant that these professionals beready to identify children who are atrisk for being bullied because the po-tential negative health, psychological,and educational consequences of bul-lying experiences are far-reaching.

    Pediatricians can play an important rolein detecting potential victims of bullyingif they consider bullying as a possiblerisk factor in any patient with recurrentheadaches, breathing problems, poor

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  • appetite, sleeping problems, and so on.Any recurrent and unexplained somaticsymptom can be a warning sign of bul-lying victimization. Because children donot easily talk about their bullyingexperiences, pediatricians could ap-proach the issue of bullying throughgeneral questions, for example, by in-quiring about the childs experience andfriends in school. If the child seems to bewithdrawn from peers, the pediatricianshould ask for the reason and de-termine whether teasing, name calling,or deliberate exclusionmay be involved.

    Asking whether the child feels safe atschool can also allow the pediatrician togain insight into the level of concern thechild is experiencing.

    Moreover, pediatricians could rou-tinely review the warning signs ofbullying with parents to help themidentify problems with bullying theirchild may be experiencing. Preventivemeasures can also include counselingparents about bullying experiences asa risk factor for childrens well-beingand the importance of promoting

    development of social skills and as-sertiveness in their children. Pedia-tricians suggestions are likely to beparticularly effective given the highconfidence that parents usually put inthese professionals. Furthermore, par-ents should be encouraged to ask forschool support when a case of bullyingemerges. Breaking the cycle of victimi-zation through early identification andprompt intervention may prevent per-sistent physical and mental healthproblems in children who experiencebullying.

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    A Message From the Editor of Pediatrics: In its January 2013 issue, Pediatricspublished a case report entitled Lethal Effect of a Single Dose of Rasburicase ina Preterm Newborn Infant. The authors included two physicians (Patrizia Zar-amelia, MD, and Alessandra DeSalvia, PhD, MD), who disclosed that they served aspaid expert witnesses in the case reported in this article. Although the authors ofthe case report refer to the infant as our patient, Pediatrics has since learnedthat none of the authors of the case report treated the infant who is the subject ofthe case report. Pediatrics has also learned that this case is the subject ofpending criminal and civil proceedings in Italy, that Drs. Zaramelia and DeSalviawere appointed as expert witnesses for the prosecution in the criminal pro-ceedings and that the medical conclusions in the article are being contested bythe opposing parties and their experts.

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