ROB McGEE, PH.D., MICHAEL FEEHAN, DIPCLPS., SHEILA WILLIAMS, B.Sc.,AND JESSIE ANDERSON, F.R.A.N.Z.C.P.
Abstract. Although research into the continuity of disorder from childhood to adolescence is sparse, resultsfrom both longitudinal and cross sectional studies suggest that the prevalence of disorder increases for girls butmay remain more stable for boys. In this paper, the methodologies of two assessment phases of the Dunedinlongitudinal study have been equated to estimate the continuity of DSM-III disorder from ages 11 to 15. Althoughthe overall prevalence of disorder doubled between the ages, this was primarily because of an increase in nonaggressive conduct disorder and major depressive episode. The sex ratios in disorder had largely reversed from a malepredominance at 11 to a female predominance at 15. In terms of persistence, over 40% of those with disorder atage 11 were also identified at age 15. However, over 80% of those identified with disorder at 15 did not have ahistory of disorder at 11. Significant sex differences were also found in the continuity of internalizing andexternalizing disorders, with externalizing disorders showing more continuity for boys, and internalizing for girls.Logistic regression models were employed to evaluate the roles family background, academic and social competence, and early histories of behavior problems may play in the determination of disorder continuity. J. Am.Acad. Child Adolesc. Psychiatry, 1992, 31, 1:50-59. Key Words: DSM-Ill disorder, preadolescence, adolescence,longitudinal.
Estimates of the prevalence of mental health disorders inpreadolescents range from about 7% in the Rutter et al.(1970) Isle of Wight study, to 14% in the Connell et al.(1982) study of Queensland (Australia) children, to 19% inthe Miller et al. (1974) study of children in Newcastle(U.K.), to 25% in the Inner London Borough Study of Rutteret al. (1975). These estimates were based upon samples ofchildren aged about 10 to 11 years old. Investigations ofadolescent samples suggest a comparable range of estimates.For example, Leslie (1974) estimated that about 21% of 13to 14-year-olds in Blackburn (U.K.) had a disorder, whereasRutter et al. (1976) suggested that about 8% of 14- to 15year-olds in a follow-up on the Isle of Wight study had adisorder. However, the latter study also provided a correctedestimate of 21% with disorder. These figures suggest that asignificant proportion of both preadolescent and adolescentchildren have emotional and/or behavioral disorders. Thereis, however, little research to indicate the extent of continuity
Accepted September 5, 1991.Dr. McGee is a Senior Research Fellow and Mrs. Williams is a
Biostatistician, Department ofPreventive and Social Medicine, Medical School, University of Otago, Dunedin, New Zealand. Mr. Feehanis a Research Fellow in the Dunedin Multidisciplinary Health andDevelopment Research Unit (DMHDRU), Department of Paediatricsand Child Health, Medical School, University ofOtago. Dr. Andersonis a Senior Lecturer, Department ofPsychological Medicine, MedicalSchool, University of Otago.
The DMHDRU is supported by the Health Research Council ofNew Zealand and involves several departments of the University ofOtago. The authors are indebted to the many people whose valuablecontributions continue to make this on-going study possible. The authors acknowledge the help of Dr. P. A. Silva in the preparation ofthis report. Collection ofthe mental health data at age 15 and preparation of this report was partially supported by U.S.P.R.S. grants 1-23MH42723-01, l-ROI-MH43746 and MH-45070-03 from the Antisocial and Violent Behaviour Branch of the U.S. National Institutes ofMental Health.
of disorder from preadolescence to adolescence. Yet, a consideration of the degree to which disorders persist is centralto any developmental model of psychopathology. Such amodel would need to specify prevalences in disorder overtime, with particular reference to changes in prevalence,persistence of disorder, and whether or not there are differential predictors of early and late onset disorder.
The Isle of Wight studies provide the best informationconcerning changes in disorder over time in a sample drawnfrom the general population (Rutter et al., 1976). This research suggested that a "slight rise" occurred in the prevalence of disorder from preadolescence to adolescence, basedupon parent interview. The rise reflected an increase indepression and school refusal as a part of anxiety/affectivedisorder. However, if the adolescent interview was considered, then there was a significant increase in adolescence inthe number of girls with emotional disorder based uponself-report. The studies also suggested that persistence ofdisorder was associated with being male, having poor scholastic attainment, and experiencing more family difficulties.In these respects, disorders arising in adolescence differedsignificantly from those in preadolescence.
Cross-sectional studies using samples of different agesalso suggest developmental changes in the prevalence ofdisorders over time. In the Ontario Child Health Study (Offord et al., 1987), the prevalence of disorder in girls increased over one and a half fold from ages 4 to 11 to 12 to16 years. There was more conduct disorder in the older boysand girls and more emotional disorder in the older girls. Inthe same sample, Joffe et al. (1988) report a "dramaticincrease" in suicidal ideation and behavior in the girls aged14 to 16 years. On the other hand, the older boys showedless hyperactivity, less emotional disorder, and less suicidalideation than the younger boys. In the Bird et al. (1988)community survey of Puerto Rican children aged 4 to 16years, there were similar increases in conduct disorder anddepression over time. Finally, Cohen et al. (1987) compared
J. Am. Acad. Child Adolesc. Psychiatry, 31:1, January 1992
the prevalence of DSM-III-R disorders in age groups of 9 to12 and 13 to 18 years. Oppositional, conduct, and overanxious disorders were more prevalent in the older sample ofgirls compared with the younger. For the boys, no disordershowed a marked increase with age; in fact, attention deficit,separation anxiety, and overanxious disorders showed a decrease in the older group.
The above findings suggest sex related changes in theprevalences of disorder as a function of age. However, inthese broader community surveys only Rutter and colleagueshave examined the persistence and prediction of disorderfrom preadolescence to adolescence. This paper examinesmental health disorders assessed at age 11 and again at age15 years. The sample from Dunedin, New Zealand, has beenstudied longitudinally from birth to 15. The first comprehensive assessment of DSM-III using child interview and bothparent and teacher report occurred when the sample members were aged 11. The findings have been reported byAnderson et aI. (1987). At age 15, a substantial percentageof the total sample were reinterviewed, and parent reportsof behavioral and emotional problems were obtained. Theresults from this assessment are reported elsewhere (McGeeet al., 1990). Although the assessment procedures differedat the two ages, it was possible in the present study to equatethe methods for identifying disorder in preadolescence andadolescence. Broadly, the aims of this paper were two-fold.The first was to examine changes in the prevalence of disorder over time, particularly with respect to sex differences indisorder at ages 11 and 15. The second was to examine theassociation between background variables and disorder at11 and 15 years.
Method
Sample
The history and details of the Dunedin study are providedby Silva (1990). To summarize, the sample belonged to acohort born at Queen Mary Hospital, Dunedin, betweenApril 1, 1972, and March 31,1973. A total of 1,037 3-yearolds were enrolled in the Dunedin Multidisciplinary Healthand Development Study, from an eligible sample of 1,139still living in the Otago province. Those not assessed at age3 were either traced too late for inclusion or their parentsrefused cooperation. Subsequently, the sample has been reassessed every 2 years; for this paper the relevant assessments were at age 11 (N = 925, 1983-1984) and at age 15(N = 976, 1987-1988).
The Dunedin sample is primarily of European origin andcompared with the remainder of New Zealand is underrepresentative of children from Maori or other Polynesian backgrounds. Furthermore, the sample is somewhat more advan-
. taged socioeconomically when compared with the rest ofthe country (Elley and Irving, 1972).
Measures of Disorder at Age II
Full details concerning these measures are provided byAnderson et aI. (1987). Those 11-year-olds who came to theUnit were interviewed by J. A., a child psychiatrist, usingthe Diagnostic Interview Schedule for Children or DISC-C
J. Am. Acad. Child Adolesc. Psychiatry, 31: 1, January 1992
DSM-III DISORDERS FROM AGE 11 TO AGE 15
(version XIII-III, Costello et al., 1982). This is a structuredinterview assessing symptomatology for DSM-III disordersin childhood and adolescence. Each response is scored as 0for "no," 1 for "sometimes," and 2 for "yes." After theinterview was tested, the final form used at age 11 contained148 items for assessing the following disorders: attentiondeficit, conduct, oppositional, major depressive episode,dysthymia, separation anxiety, overanxious, avoidant, simple and social phobia, obsessive-compulsive, and psychoticdisorders.
The parent (generally the mother) completed the Rutteret aI. (1970) Child Scale A, a 31-item questionnaire coveringbehavioral and emotional problems. Two additional questionnaires were given to the parents, one to assess attentiondeficit problems based directly upon DSM-III criteria(McGee et al., 1985), and one to assess depression andrelated problem behaviors (Anderson et al., 1987). Thesetwo questionnaires were included to supplement the ChildScale A. Parents were also asked to describe "any othersignificant behavior problems" over the last year and anyhelp or advice they had sought in the last 2 years for theirson or daughter from various medical, social welfare, oreducational agencies. The child's teacher also completed the26-item Child Scale B of Rutter and colleagues and theattention deficit questionnaire.
Measures of Disorder at Age 15
Owing to time constraints on the testing schedule and theauthors' desire to include other measures relating to mentalhealth, the DISC-C for the age 15 assessment was shortened.The modifications are fully described by McGee et al.(1990), and a copy of the briefer measure and some of thepsychometric properties of the DISC-C are available uponrequest. The abbreviated scale consisted of 110 items thatcovered all the disorders included at age 11 except for obsessive-compulsive and psychotic disorders. Questions relatingto these were omitted because of the rarity of the disorders.No preadolescents were identified with these disorders atage 11. The focus in this research has been to concentrateon more commonly occurring conditions.
The parent completed the Revised Behavior ProblemChecklist or RBPC of Quay and Peterson (1987). This is a77-item questionnaire scored for subscales of conduct disorder, socialized aggression, anxiety withdrawal, attentionproblems-immaturity, motor excess and psychotic behavior. The parents were also asked whether they thought theirson or daughter had some "significant behavior or emotional problems at the present time" and to describe thenature and duration of such problems; whether their son ordaughter had been in contact with the police; and, as at age11, whether they had sought help or advice for their son ordaughter. No teacher questionnaires were administered atage 15; at this age, adolescents have several teachers anduse of a questionnaire was deemed inappropriate.
Identification of Disorder at Ages 11 and 15
To best examine the nature and continuity of disorder atthese two ages, the authors believed it desirable to equateas far as possible the methods used to identify disorder at
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both ages. Essentially this required the reidentification ofdisorder at age 11 with the criteria used at age 15. Consequently, the method used to identify disorder at age 15 isbriefly described and then how this method at age 11 wasapplied is explained.
At age 15, the identification of disorder was based primarily on the adolescent's own self-report meeting DSM-IIIcriteria for the disorder. The parent measures were essentially used to confirm the adolescent's self-report. This procedure was used because the RBPC and other measures didnot provide full diagnostic criteria. In the case of adolescentself-report on the modified DISC-C, only responses of "2,"a definite "yes," were used to indicate the presence of acriterion symptom. Disorder was identified where the requisite number of DSM-III criterion symptoms were present.
For the parent report, six "rules" for confirmation of theadolescent self-reported disorder were developed, and theserules and the rationale for this approach are fully describedby McGee et al. (1990).
1. Disorder was considered confirmed if the relevantRBPC subscale score fell at or above 1.5 standard deviationsfrom the same sex mean. The 1.5 standard deviation cutoff identified about the upper 10% of the score distributionsand was consistent with cut-off scores in the RBPC manual.Although the RBPC does not have an "oppositional" scaleper se, such a scale was constructed from the items relatingto "staying out," "tantrums," "disobedient," "negative,""impertinent," "argues," "persists-nags,"and "refuses directions" (these are conduct disorder subscale items). Thisscale was used for the confirmation of oppositional disorderand nonaggressive conduct disorder only.
2. Disorder was considered confirmed if the total scoreon the RBPC fell at or above a similar criterion (43 or morefor boys and 39 or more for girls) and relevant subscaleitem(s) were scored "2," "yes, certainly applies."
3. The parent reported a significant behavioral or emotional problem relevant to the adolescent self-reported disorder.
4. The parent reported referral for help.5. Conduct disorders could be specifically confirmed by
parent report of police or judicial contact.6. We also identified disorder in those instances where
the diagnostic criteria were met by combining the adolescentself-report and the parent report.
Anderson et al. (1987) identified disorder at 11 on thebasis of the full DISC-C and both parent and teacher report.To equate the two ages, the data at age 11 were reanalyzedusing only the DISC-C and parent scales. As teacher reportswere unavailable at 15, they were not used in the reexamination of the age 11 data. In the first instance, only thoseDISC-C items that had formed the briefer DISC-C at age 15were used. Consequently, criteria for self-reported disorderwere the same at both ages. For parent confirmation, similar"rules" to those outlined above were used. However, itwas not possible to use exactly the same items to constructsubscales. Rather, all the parent report items were pooledfrom the Child.Scale A, attention deficit and depressionscales, and then scales were constructed measuring "con-
52
structs" similar to those at 15. A worry-fearful scale wasformed from the eight items: "worries," "miserable,""fearful," "fussy," "withdraws," "feels worthless,""feels hopeless," and "tearful at schooL" This scale consisted of the "core" items from the "worry-fearful" factoridentified by McGee et al. (1985) together with items fromthe age 11 depression scale. Coefficient alpha, a measure ofthe internal consistency of the scale, was 0.72. A score of 5or above for boys and girls confirmed anxiety or depressivedisorders at age 11 (cut-off criterion: mean + 1.5 SD). Aninattention-hyperactivity subscale was formed from the 15inattention, impulsivity, and hyperactivity items assessingattention deficit disorder based directly on DSM-III criteria;cut-off scores were 15 or above for boys and 13 or abovefor girls. Coefficient alpha for the subscale was 0.90. Anantisocial scale was formed from the 12 items: "destructive," "fights," "steals," "bullies," "lies," "tantrums,""irritable," "disobedient," "not liked," "talks back,""provokes arguments" and "truants." This scale was madeup of nine core items from the McGee et al. (1985) "antisocial behavior" factor together with the latter three items.Coefficient alpha for the antisocial scale was 0.83. Cut-offscores were 9 or above for boys and 8 or above for girls.Finally, cut-off scores were obtained for a total score basedon the sum of the above three subscales of 26 or above forboys and 22 or above for girls. Parent reports of significantbehavior problems and help-seeking at age 11 were used inthe same way as had been done at 15 years. Once again,disorder was identified in those instances where the combined child and parent report fulfilled DSM-III criteria.
Background Variables
Four main variables were chosen to investigate the relationship between disorder at the two ages, and family background, academic and social competence, and a history ofearly behavior problems. A measure of cumulative familydisadvantage to age 11 was used to assess family background. The measure is described by Williams et al. (1990)and was based upon indicators of family disadvantage suchas low socioeconomic status, solo parenting, parental separations, poor maternal mental health, poor family social support, parents seeking marriage guidance, low maternal cognitive ability, mother being young, and frequent changes ofaddress and/or school. A score of 6 orabove on this measureidentified 15% of the sample and was used to indicate highfamily disadvantage. A cut-off score of 6 or more was alsoassociated with higher levels of disorder (Williams et aI.,1990).
Academic background was assessed by reading performance at ages 9 and 11, and McGee et al. (1988) identified80 reading disabled boys and girls over these two ages,representing 9% of the sample. Social competence at age 11was based upon a lO-point index described by McGee andWilliams (1991). This index assessed attachment to familyand friends, involvement in activities or hobbies, attitude toschool, having a part-time job or regular chores, and levelof self-esteem. A score of 6 or less identified 30% of thesample and was used to indicate low social competence.This level of cut-off score was used in the authors' earlier
TABLE 1. Prevalence of DSM-lll Disorders at Ages11 and 15 Years
over the two ages, there was a different pattern for parentconfirmed disorder. Girls showed a two-and-a-half fold increase in confirmed disorder from age 11 to 15; for boysthe prevalence of confirmed disorder at each age was similar.
Have there been differential increases in the numbers ofboys and girls with particular disorders from age 11 to IS?An examination of sex differences by individual disorderswas restricted because of the small number of boys and girlsin several of the categories shown in Table 1. Overall, boysoutnumbered girls at age 11 in each of the 10 categories ofdisorder except for separation anxiety and simple phobia.By age 15, girls outnumbered boys in all categories exceptattention deficit and aggressive conduct disorder. The disorders were grouped into four, mutually exclusive, generalordered categories of attention deficit, conduct oppositional,depression, and anxiety disorders. Adolescents with "multiple" disorders across categories were assigned to the attention deficit group in the first instance, those with disordersof conduct were assigned to the conduct oppositional groupand so on, as appropriate. Table 2 shows the numbers ofboys and girls in each category at the two ages. For bothconduct oppositional and depressive disorders, there was areversal of the sex ratios from 11 to 15, with proportionallymore girls showing these disorders at age 15. For anxietydisorders, on the other hand, both boys and girls had moresuch disorders (primarily overanxious and phobia disorders)at the later age.
Disorder from Age 11 to 15
Of the 66 preadolescents with any DSM-III disorder atage 11, 28 or 42% also had a DSM-III disorder at age 15;there was no sex difference in the proportion with disorderat both ages. Of the 147 adolescents with disorder at 15, 119or 81% had not been identified as having a disorder at age11. Similarly, in the case of confirmed disorders at age 15,the majority of adolescents were not identified as showinga disorder at 11. That is, whether parent confirmed or selfreported, most disorders at age 15 had risen de novo.
To examine more closely changes in disorder from 11 to15, two wave-two variable models were fitted to the data(Plewis, 1985). The aims of the models were as follows: (1)to provide an estimate of the strength of the associationbetween disorder at 11 and disorder at 15; and (2) to examine
work on the association between competence at age 11 andlater disorder (McGee and Williams, 1991). Finally, a history of early problem behaviors was based upon parent andteacher reports using Rutter et al.'s (1970) Child Scales Aand B, respectively, at ages 5 and 7. McGee et al. (1983)identified 11% of the sample as showing persistent parentand/or teacher reported problems over these two ages.
General Procedure
The general procedures for assessment were similar atboth ages. The questionnaires, explanation of procedures,and consent forms were sent to the parents a few weeksbefore the child's attendance at the Dunedin Unit. Writtenconsent was obtained from the parent at both ages (theauthors also obtained written consent from the adolescentsat age 15). Those able to attend the unit did so for a day ofhealth, cognitive, motor, educational, physical, and mentalhealth assessments. At age 11, those unable to attend theunit were assessed wherever possible by Department of Education psychologists. This assessment could not include theDISC-C interview. At age 15, the mental health assessmentsincluding the brief DISC-C were given to those who wereinterviewed elsewhere. Consequently, fewer were interviewed at 11 (N = 792) than at 15 (N = 962).
Results
Prevalence of Disorder at Ages 11 and 15
Self- and parent reports at both ages were available for750 adolescents (393 boys and 357 girls). At age 11, 66sample members or 8.8% had a total of 98 DSM-III disorders. At age 15, 147 adolescents or 19.6% of the sample hada total of 182 disorders. Over time, there was a two-foldincrease in the proportion of the sample with disorder. Table1 shows the prevalence of individual disorders at the twoages. To compare the prevalences over time, 95% confidence intervals for each disorder were calculated, basedupon the assumption that presence of disorder conformedto a poisson distribution. On the basis of nonoverlappingconfidence intervals, there was a significant increase in theprevalence of nonaggressive conduct and major depressiveepisode from 11 to 15 years.
Sex Differences in Disorder
At age 11, the ratio of boys to girls with any kind ofdisorder was 1.3:1; at age 15, a reversal in the sex ratio ofthose with disorder occurred and the ratio of boys to girlswas 0.7:1. Figure 1 shows the prevalence of nonconfirmed(i.e., self-reported) and parent confirmed disorders for boysand girls separately at each age. The results were analyzedusing a cumulative logit model for repeated, ordered categorical data (Agresti, 1989). For this analysis, it was assumed that the categories of disorder (i.e., none, nonconfirmed, and parent confirmed) were ordered categories. Theanalysis indicated a significant sex X age interaction withX2 (1 df) = 7.15, p < 0.05. This interaction was due to thedifferential pattern for parent confirmed and nonconfirmeddisorders over time. Although the prevalence of the latterincreased approximately four-fold for both boys and girls
FIG. 1. Sex differences in the prevalences of confirmed and nonconfirmed disorder at ages 11 and 15.
the association between the background variables in childhood and preadolescence and disorder at the two ages. Giventhe changes in externalizing disorders (particularly conductand oppositional disorders) and internalizing disorders (anxiety and depression) over the two ages as shown in Table 2,it was decided to examine the persistence of these two typesof disorder. It was not possible to simultaneously includethe distinction between confirmed and nonconfirmed disorders in the models. However, by examining internalizingand externalizing disorders, it was possible to look at "whattype of disorder leads to what." For this analysis, thoseadolescents with coexisting externalizing and internalizingdisorders were identified as externalizing.
The basic path diagrams for the models are shown inFigure 2, with the results presented separately for boys andgirls. The' 'paths" show the strength of the predictive relationships between type of disorder at age 11 and type ofdisorder at age 15.The overall analysis is based upon logisticregression; the figures shown for the various paths are oddsratios (OR), each indicating the odds of showing an externalizing or internalizing disorder at 15 given the presenceof an externalizing or internalizing disorder at age 11. Asmay be seen from the two diagrams, persistence of disorderdiffered for boys and girls. Externalizing disorder at age 11did not predict externalizing disorder at 15 for girls, andfor boys, internalizing disorder at 11 was not significantlypredictive of internalizing disorder at 15. However, girlswith an internalizing disorder at age 11 were over six timesmore likely than those without disorder to have an internalizing disorder at 15. For boys, externalizing disorder at 15was strongly predicted by both types of disorder at 11.
Unfortunately, cell sizes were too small to include morethan one background variable in the models simultaneously.
54
Consequently, it was possible only to examine the four background variables in separate models. The inclusion of familydisadvantage, reading disability, poor social competence,and history of early behavior problems as "exogenous"variables in the models depicted in Figure 2 did not substantially alter the obtained OR. For this reason, the adjustedOR are not presented. The implication of this finding is thatthese background variables did not significantly alter thestrength of the predictive relationship between disorder atage II and disorder at 15.
The next phase of the analysis was to examine the relationships between each of the four background variables anddisorder at 11 and 15. Table 3 shows the OR for disorder atboth ages for the four preadolescent background variables.The OR for age 15 were adjusted for the relationship at age11. Inspection of the table indicates a similar pattern forboys and girls at age 11, with all four variables being associated with an increased rate of disorder in preadolescence . Ahistory of early problem behavior was most strongly associated with disorder at age 11; children with behavior problems in the early school years were nearly six times morelikely to have a disorder at age II than those with no problems. This relationship was somewhat stronger in the case ofexternalizing disorder at age II. Furthermore, boys showingbehavior problems in the early school years were twice aslikely to have a disorder at age 15, after adjusting for disorder at age 11. (They were over three times more likelyto have an externalizing disorder at age 15.) Early familydisadvantage was also strongly associated with disorder atage 11 (overall sample OR = 4.3) and was also predictiveof disorder in boys at age 15. Poor preadolescent socialcompetence was significantly related to disorder at age 11(overall OR = 3.3). Although not predictive of disorder in
FIG. 2. Path diagrams for internalizing (INT) and externalizing (EXT) disorder from ages 11 to 15. Paths are shown as odds ratios; * indicatesodds ratio significant, p < 0.05.
general at age 15, preadolescent competence may be moreassociated with later externalizing problems (McGee andWilliams, 1991). After adjusting for the association withdisorder at age 11, boys with poor preadolescent social competence were three times more likely to have an externalizing disorder at age 15 compared with boys having goodsocial competence (p < 0.05). Reading disability, althoughassociated with disorder at age 11 (overall OR = 3.1), wasnot predictive of disorder at age 15, after adjusting for age11. Comparisons between externalizing and internalizingdisorders at age 11 were somewhat hampered by small cellsizes in several instances (e.g., by the low prevalence ofexternalizing disorders among the girls). In general, however, the four background variables were more strongly related to externalizing disorders.
New Disorders at Age 15
A total of 119 adolescents (12% of the boys and 20% ofthe girls) had a disorder at age 15 but not at 11. The relationships between background variables of family disadvantage,reading disability, and poor social competence at age 15 anddisorder were examined. Family disadvantage was definedin terms of a score of 2 or more on a six-point index at age15 (McGee et al., 1990). Reading disability at age 15 wasdefined in terms of a reading score on the Burt Word Reading Test (Gilmore et aI., 1981) at or below the readinglevel of 12-year-old boys and girls. Finally, poor socialcompetence at age 15 was defined by a score from 0 to 9on a 13-point index similar to that used at age 11 (McGeeand Williams, 1991). Family disadvantage was significantlyassociated with disorder for both boys (OR = 3.9) andgirls (OR = 3.3). Reading disability at 15 was significantlyassociated with disorder for boys (OR = 2.2) but not for girls(OR = 1.1). Finally, poor social competence was related todisorder for both boys (OR = 3.0) and girls (OR = 2.4), P< 0.05 in all cases. Once again, these relationships betweenbackground variables at age 15 and disorder were strongerfor externalizing types of problems.
Some Methodological Issues
The comparison of the present findings at age 11 with
J.Am. Acad. Child Adolesc. Psychiatry, 31..1, January 1992
those reported by Anderson et al. (1987) indicated that theauthors were potentially underestimating the prevalence ofattention deficit disorder and oppositional disorder. Anderson et aI. identified disorder at age 11 based upon self-,parent, and teacher report; the present study was restrictedto self- and parent report for comparability with age 15.Closer inspection of the age 11 results indicated that byexcluding teacher reports the authors were not identifyingsignificant numbers showing attention problems in the classroom. On the other hand, the methodology in this paper didnot appear to be underidentifying large numbers of childrenwith parent-identified attention deficit disorder.
A second concern was that the procedure would underestimate the prevalence of oppositional disorder by failing toidentify children on the basis of parents' report. Inspectionof the latter at ages 11 and 15 indicated that this was trueto some extent. Based upon ratings of irritability, tantrums,disobedience, talking back, and argumentativeness at bothages, 1.7% of the sample was identified as showing parentreported, oppositional behaviors at age 11, and 2.5% atage 15 who were not already identified with disorder wasidentified. These findings parallel the increase in oppositional behavior over time reported in Table 1.
Finally, it was possible to compare the prevalence ofDSM-III disorder at age 15 in the 750 adolescents for whomcomplete data were available and the 193 for whom selfand parent report were available at age 15 but not age 11years. Overall, the prevalence of disorder of 19.6% in thesample of 750 compared with 28.5% in the sample of 193with missing data, with X2 (l dj) = 6.70, p < 0.05. Thissuggests that those adolescents with missing mental healthdata at age 11 had significantly more overall disorder at 15years. However, a comparison in terms of the prevalence ofconfirmed disorder (9.2% vs 11.4%, respectively) was notsignificant with X2 (1 dj) < 1.0, p > 0.05. This suggests thatthe difference in prevalence of disorder at 15 was associatedwith nonconfirmed (primarily anxiety/depression) disorder.
Discussion
At the outset, it should be noted that there are some
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T ABLE 2. Numbers of Boys and Girls in the Attention Defi cit,Conduct Oppositional, Depressive, and Anxiety Categories at
11 and 15 Years
Age 11 Age 15
Disorder Boys Girl s M:F Boys Girls M:F
Attent ion deficit II 2 4.7:1 7 2 3.0:1Condu ct oppositional 14 5 2.6:1 24 33 0.7 :1Depression 5 I 4.3:1 7 15 0.4:1Anxiety 9 19 0.4 :1 24 35 0.6:1Total 39 27 1.3: I 62 85 0.7:1
TABLE 3. Preadolescent Background Variables and Disorder atAges 11 and 15 (Results are Shown as Odds Ratios)
Risk of Disorder (odds ratios)
Age 11 Age 15
Background Variable Boys Girls Boys Girls
Family disadvantage 4.1* 4.6* 2.1* 1.5Reading disability 2.9* 3.5* 1.2 1.4Poor social competence 4.2* 2.3* 1.5 1.2History of behavior problems 6.4* 4.7* 2. 1* 1.9
*Odds ratio values significant, p < 0.05.
methodological limitations in the present study that willinfluence the conclusions. Both Anderson et al. (1987) andMcGee et al. (1990) have presented prevalence data formental health disorders at age 11 and 15 years, respectively.The aim of the present study was not to report two newsets of prevalence figures. Rather, the aim was to examinechanges in the prevalence of disorder over time. One strategy open to us was to simply examine prevalence changesbased upon the different methodologies described in the twooriginal papers. However, Rutter (1989) has emphasized theimportance of having comparable measures and proceduresacross different ages to study such prevalence changes , andthis approach was adopted in the present study.
In identifying disorder, a gre ater emphasis has beenplaced on the child/adolescent report . The main reason forthis has been a pragmatic one; the parent questionnaire s donot provide DSM-III criteria for disorder. Nevertheless, thereis evidence to suggest that child and adolescent reports ofdisorder are reliable (Reich and Earls, 1987). By focusingupon self- and parent report at age 11, it is clear that manyof the preadolescents with attention deficit disorder according to teacher report were not identified. Furthermore ,oppositional disorder may well have been underidentifiedby emphasizing self-reports. Loeber et al. (1989) found that7- to 12-year-old boys underreport (at least in comparisonto parents) oppositional behaviors. Examination of parentaldata in the present study suggested some discrepancies between parent and self-report , but parent identified oppositional disorder showed the same increase over age. Finally,the authors' analysis of missing values suggested that thosel l- year-olds with incomplete data had higher rates of DSMIII disorder (particularly nonconfirmed disorder) at age 15.It is possible that they may have had a higher rate of disorderat 11.
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Overall, there was a clear increase in the prevalence ofDSM-III disorders with age; some 9% of the sample had oneor more disorders at age 11 compared with nearly 20% byage 15. The increase was most apparent with self-reporteddisorders; these increased nearly four-fold for both boysand girls. At age 11, about two-thirds of all self-reporteddisorders were confirmed by parent report, and, as Figure 1indicates, parent confirmation was particularly evident forpreadolescent boys. By age 15, less than half of all adolescent reported disorders were being confirmed by the parent.Girls also showed a marked increase in the prevalence ofparent-confirmed disorders over time, suggesting that theincreased rate of disorder among girls was not simply because of a change in girls' "response bias" with age. Theproportion of boys with parent-confirmed disorders, on theother hand, was similar at the two ages.
The results of this study confirm and extend the originalfindings of Rutter et al. (1976) on the Isle of Wight insuggesting an increase in the prevalence of self-reporteddisorders among adolescents of both sexes. The two disorders to show the most marked increases in prevalence weremajor depressive episode and nonaggressive conduct disorder. The change in the prevalence of major depressive episode is of some interest. First, it stands in contrast to dysthymia, which had a similar prevalence at the two ages. Second,at age 11, depression in general showed a male predominance, whereas, by age 15, there was a female predominance. In the Isle of Wight, there was a similar increase inaffective disorder (Rutter et aI., 1976). Pearce (unpublishedthesis quoted by Rutter, 1988) found that in a clinic sample,depressive disorder was more common among boys beforepuberty, but after puberty, it was more common among girls.The authors observed this same pattern in their sample fromthe general population. Third, the findings in the presentstudy suggest that major depressive episode is relatively rarein childhood and that it tends to coexist with other disorders.By age 15, although depressive disorders in general showedhigh comorbidity with other disorders, major depressive episode was much more likely to occur as a single disorder.
These differences raise the important question as towhether major depressive episode in childhood is a similardisorder to later onset depressive episodes in adolescenceand adulthood. Seifer et al. (1989) have recently argued thatthere is little empirical support for a construct of majordepressive episode in childhood . Rather, there is better support for a dimension of dysthymic symptoms. Anderson etal. (1987) reported that among the Ll- year-olds in theDunedin study, dysthymia was about four times more prevalent than major depressive episode. The findings of the present study add to these earlier results from the Dunedin research that call into question the assumption that child andadolescent/adult depression are qualitatively similar disorders (also McGee and Williams, 1988).
The other disorder showing perhaps the clearest increasein prevalence over time was nonaggressive conduct disorder .In part, this reflects the greater availability of alcohol andillicit drugs (primarily marijuana) at adolescence . However,in the sample as a whole, there have been considerableincreases in the occurrence of petty theft, truancy, glue sniff-
J.Am. Acad. Child Adolesc. Psychiatry, 31: 1, January 1992
ing, and the use of cannabis, other illegal drugs, and alcoholacross the adolescent years (Moffitt and Silva, 1988). Thisseems to have been particularly so for adolescent girls. Thefindings with respect to nonaggressive conduct disorderstand in contrast to the aggressive type, which showed noincrease in prevalence over time and was a disorder of boys.Furthermore, inspection of individual aggressive behaviors,such as using weapons, threatening others, setting fires, anddamaging property, indicated little increase across the adolescent years.
Whereas no single anxiety disorder showed a significantincrease in prevalence from age 11 to age 15, it is worthnoting that as a group, the prevalence of anxiety disorders(i.e., overanxious disorder, and simple and social phobias)doubled over time. In general, there has been little researchon anxiety disorders and developmental trends (Rutter,1989). In contrast to depressive disorders, anxiety disorderswere more common among girls at both preadolescence andadolescence. Ollendick et al. (1985) have reported a slightdecrease in fears from childhood to adolescence, usingcross-sectional data. The results in this study suggest anincrease in both fears and worries from 11 to 15 years.Furthermore, the nature of these fears changed from primarily fears of the dark, heights, and animals at age 11 to fearsspecifically relating to social situations and "agoraphobic"situations. This pattern of change agrees with the findingsof studies investigating retrospective recall of age of onsetof specific phobias in patient groups (e.g., Marks and Gelder,1966). By contrast, separation anxiety showed equivalentprevalence at the two ages.
How persistent are disorders over time? Overall, four ofevery 10 preadolescents with a disorder at age 11 also hada disorder at age 15. Although the authors were unable toinvestigate the continuity of individual disorders, they wereable to provide some information on "what leads to what."For boys, externalizing disorders showed significant continuity across the ages. What is also of note is that the boyswith an internalizing disorder at age 11 were nearly sixtimes more likely than those without disorder to have anexternalizing disorder (possibly in combination with an internalizing one) at 15. Thus, for at least some adolescentboys, internalizing problems precede the antisocial ones.Elsewhere, the authors have documented the long-term association between depression and antisocial behavior in boys(McGee and Williams, 1988). Puig-Antich (1982) hypothesized that depressive syndromes may play an important roleas triggers for the development of conduct disorder, and theresults in the present study are consistent with this hypothesis. Girls showed little continuity of externalizing problems,which may be a function of the low number of girls withsuch problems at 11. However, girls with internalizing disorders at age 11 were six times more likely to have a similarkind of disorder at age 15.
An examination of preadolescent family disadvantage,reading disability, poor social competence, and a historyof problem behaviors indicated that these variables weresignificantly associated with preadolescent disorder. However, they did not affect the strength of the predictive relationships between disorder at ages 11 and 15. That is, these
variables may have their greatest influence on the onset ofdisorder rather than the course of disorder. This is preciselythe conclusion drawn from the Isle of Wight research (Rutteret aI., 1976). Although these early background variableswere largely unrelated to disorder at age 15 in girls, oncetheir relationship with disorder at 11 was taken into account,a history of early problem behavior, family disadvantage,and poor preadolescent social competence remained independently predictive oflater externalizing disorders in boys.At preadolescence, few differences were noted between boysand girls in the strength of relationships between backgroundvariables and disorder. Williams et al. (1990) have recentlyexamined risk factors for preadolescent disorders in moredetail and have reported similar results for boys and girls.However, the present findings suggest that the continuedinfluence of early behavior problems, family disadvantageand poor social competence into adolescence is moremarked for boys. The determinants of later externalizingbehaviors in adolescent girls do not appear to be found inchildhood.
New disorders at age 15 were strongly associated withboth family disadvantage and poor social competence at thatage. The critical components of family disadvantage appearto be poor family interpersonal relationships, maternal depression, and parental separations (Mcflee et aI., 1990;McGee and Stanton, unpublished manuscript). Similarly,poor social competence reflects low involvement and attachment to family, friends, school, work, and activities. Thesefindings are hardly surprising, and the more crucial questionis "what leads to what?" McGee and Williams (1991) pro-
. vided some evidence that early poor social competence onlypredicts later disorder among those already with a disorderamong those already with a disorder at preadolescence. Furthermore, at least for boys, poor social competence in adolescence may flow from antisocial behavior. Whereas Rutteret al. (1976) found no relationship between late onset disorder and later reading problems, the present results suggestthat poor reading skills at age 15 are associated with lateronset antisocial behavior among boys.
A question to be posed but perhaps not answered concernsthe reason for the reversal in sex differences from a male tofemale ratio of 1.3:1 in preadolescence to 0.7:1 in adolescence. In particular, why do girls show a marked increasein depressive disorders and nonaggressive conduct and oppositional disorders at this age? The results in this studyindicate that girls are more anxious in preadolescence andremain so in adolescence. This would suggest that depressive and anxiety disorders are either qualitatively different disorders or that anxiety disorders precede depressivedisorders in girls. The latter is clearly a testable hypothesis.One avenue being explored is the idea that girls in adolescence are more susceptible to stress and disorder becausegirls' self-esteem at that age is more narrowly based thanboys (Williams and McGee, 1990). Self-esteem and depression are significantly associated for both boys and girls. Theresults in this study suggest that adolescent girls may bemore vulnerable than adolescent boys to threats to their selfimage.
With regard to clinical implications, the results in this
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report indicate that early intervention may have longer-termbenefits beyond the immediate amelioration of presentingproblem behavior or psychiatric symptomatology. Given thedegree of continuity between disorder at 11 and 15, it islikely that effective treatment obtained in preadolescencemay have benefits in reducing the risk of subsequent disorder (particularly for boys). Similarly, as early problem behavior was strongly predictive of disorder at age 11 andat age 15, intervention in early childhood may reduce theincidence of disorder in preadolescence and adolescence.In terms of community-centered intervention, the authors'results would suggest that efforts aimed at prevention inchildhood could well have significant gains in reducing theprevalence of externalizing disorders for boys in adolescence. This would be true for secondary prevention aimedat identifying "at risk" children and primary preventionprograms whereby all children receive training in life skillsor "social competence" (Zax and Specter, 1974). Empiricalevidence for the effectiveness of primary and secondaryprevention models with children is favorable (Kendall andNorton-Ford, 1982). Although some researchers have recently argued that contact with mental health professionalsin childhood can have adverse longer-term outcomesthrough labeling effects (Palamara et al., 1986), results fromthe Dunedin study suggest that childhood contact with helping professionals serves to reduce the risk of disorder up to5 years later (Feehan et al., in press). The findings of thepresent study also suggest clear developmental changes inthe pattern of psychopathology between preadolescence andadolescence. Given such changes and associated developmental differences in cognitive ability and social functioning, intervention techniques may have different appeal, compliance, and effectiveness across these periods ofdevelopmental change (Harris, 1983). Further clinical research is warranted to determine the effectiveness of alternate treatment technologies in dealing with psychopathologyat different developmental periods.
In summary, this longitudinal study found an increase inthe prevalence of DSM-lII disorders from the preadolescentto the adolescent years. Disorders evident at age 11 showed arelatively moderate level of persistence across the adolescentyears, but many new disorders appeared in adolescence. Thenext phase of this study will be to examine the continuityof disorders as these adolescents become 18 years old.
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