Department of Child and Adolescent Psychiatry, Institute of Psychiatry, London
Office for National Statistics, London
Department of Child and Adolescent Psychiatry, Institute of Psychiatry, London
Correspondence: Isobel Heyman, Department of Child and Adolescent Psychiatry, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK. Tel: 020 7848 0481 ; fax: 020 7708 5800; e-mail: i.heyman{at}iop.kcl.ac.uk
Declaration of interest None; the epidemiological study was funded by the Department of Health.
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ABSTRACT |
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Aims To establish the prevalence and associates of OCD in young people aged 5-15 years.
Method A nationwide (UK) epidemiological study of rates of psychiatric disorder in 5- to 15-year-olds (1999 British Child Mental Health Survey): 10 438 children were assessed.
Results Twenty-five children with OCD were identified (weighted overall prevalence 0.25%; 95% CI 0.14-0.35), with prevalence rising exponentially with increasing age. Compared with normal controls, children with OCD were more likely to be from lower socio-economic class and of lower intelligence. Only three of these children had been seen by specialist children's services.
Conclusions Although OCD is rare in young children, the rate increases towards the adult rates at puberty. Children with OCD have additional psychosocial disadvantage. The majority of the childhood cases identified in this survey appear to have been undetected and untreated.
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INTRODUCTION |
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METHOD |
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Sample
The parents of children in the UK are entitled to receive child benefits.
The centralised computerised records from the Child Benefit Register (CBR)
were used as a sampling frame to select children aged 5-15 years throughout
England, Wales and Scotland. Families with no detailed postal code in the
database or those subjected to a current revision of their record (i.e. death
of the child, changing address) were excluded. The total number finally
included in the sampling frame was 6 422 202, representing an estimated 90%
coverage of the whole population. The sampling frame was stratified further by
the Regional Health Authority, and within that by socio-demographic groupings.
Postal sectors then were selected at random within that frame, with a
probability proportional to the size of the sector. To facilitate the
logistics of the survey, a few areas were oversampled but weights were
introduced in the analysis to adjust for unequal sampling probabilities. From
the final list of 475 postal sectors selected from the 8265 sectors covering
the whole country, the CBR was instructed to sample 30 children within each
postal sector and a letter subsequently was sent to the families by the CBR on
behalf of the Office for National Statistics (ONS) survey team. Of the 14 250
families contacted, 931 parents (6.5%) chose to opt out by calling the CBR and
a further 790 addresses (5.5%) were found to be incorrect. This left a sample
of 12 529 children eligible for interview.
Instruments
The diagnostic interview used in this survey is a new instrument
(Development and Well-Being Assessment: DAWBA) combining the features of
structured and semi-structured interviews
(Goodman et al,
2000). The DAWBA is administered by trained interviewers, who
interview parents about psychiatric symptoms and their functional impact.
Interviewers also enter on the computer a verbatim account of parental
descriptions of positive symptoms, which are elaborated by open-ended
questions and supplementary prompts. A teacher questionnaire on common
symptoms and their impact is included. A DAWBA module for direct interview of
subjects is available for 11- to 16-year-olds. Most common psychiatric
disorders are covered by the DAWBA. Diagnoses subsequently are generated by
computer algorithms based on DSM-IV
(American Psychiatric Association,
1994) and the Tenth Revision of the International Classification
of Diseases (ICD10 Diagnostic Criteria for Research;
World Health Organization,
1993) using the information from all available informants. These
computer-generated summary sheets and all interview data subsequently are
reviewed by experienced clinicians, who confirm or overturn the
computer-generated diagnoses. The reliability of clinical diagnosis was
assessed by two clinicians who, independently, rated 500 randomly chosen
subjects. The kappa statistic for chance-corrected agreement for the presence
or absence of any DSMIV diagnosis was 0.86 (95% CI 0.78-0.95).
Although the main focus of the survey was on common child psychiatric disorders, a screening question was introduced in the DAWBA to detect possible obsessivecompulsive symptoms. This question was preceded by an explanation as follows: "Many children have some habits or superstitions, such as not stepping on the cracks in the pavement, or having to go through a special goodnight ritual, or having to wear lucky clothes or to have a lucky mascot for exams or football/netball matches. It is also common for children to go through phases when they seem obsessed by a particular subject or activity. I want to ask whether [Child] has rituals or obsessions that go beyond this". If there was a positive response to the screening question "Overall, does [Child] have rituals or obsessions that upset him/her, waste a lot of his/her time, or interfere with his/her ability to get on with everyday life?" then more detailed parent and child descriptions of the child's past and current levels of obsessivecompulsive phenomena were obtained.
Other survey instruments used in this analysis were the parent, teacher and youth (for children aged 11 years or more) extended versions of the Strength and Difficulties Questionnaire (SDQ; Goodman, 1999). The SDQ is a brief screening measure enquiring about psychiatric symptoms and positive attributes and assessing the impact of the psychiatric symptoms. In addition to the total score, five sub-scores are derived that tap emotional state, conduct, hyperactivity, prosocial behaviour and peer relationships. The behaviour and the impact scores have been shown to have good reliability and validity (Goodman, 1999). If children had obtained a high score on the emotional sub-scale of the SDQ, parents were also asked in more detail about OCD symptoms, irrespective of whether the response to the OCD screening question in the DAWBA was positive. In addition, parents completed a 12-item self-report measure that assesses common psychological symptoms for the current period (GHQ12; Goldberg & Williams, 1988).
Intelligence
Survey children of all ages were administered the British Picture
Vocabulary Scale (BPVS11; Dunn
et al, 1997) and reading and spelling tests from the
British Ability Scales (BASII;
Elliott et al, 1996).
The BPVS IQs were available for all 25 of the children with OCD.
Data collection procedure
Lay interviewers (about 300) regularly involved in the Office for National
Statistics surveys were used to collect survey data. Special attempts were
made to trace families whose addresses or names had changed. Interviewer
training emphasised the need to obtain respondents' descriptions of any
problems and concerns in their own words. Interviewers first completed the
face-to-face interview with the main caregiver (90% mothers) and permission
subsequently was sought to ask questions of the sampled child. Children aged
11-15 years had a private face-to-face interview. At the end of the interview,
parents were asked to nominate a teacher who knew their child well and to whom
the SDQ subsequently was mailed, with a reminder letter if necessary.
Statistical analyses
Two weights were devised to adjust for unequal probability of postal sector
selection in the sampling frame and to compensate for differential response
rate by region. Then, adjustment weights were used to correct for non-response
bias, with the age and gender distribution of survey respondents being equated
to the population structure as determined from the 1991 Census. All prevalence
estimates were calculated with the weighted sample, and asymptotic 95%
confidence intervals were obtained with Stata version 6 software
(Stata Corporation, 1997). The
remaining analyses were conducted on unweighted data because further analyses
of the survey showed small design effects on most estimates. A conventional
P value of 0.05 was retained as the level of statistical
significance.
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RESULTS |
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All the cases given a diagnosis of OCD by the survey team were reviewed by an independent child psychiatrist with a special interest in OCD (I.H.). The initial diagnostic evaluation was confirmed in 96% of the cases. One child was excluded from the original subset thought to have OCD, and one child from the survey in whom the diagnosis had been uncertain was added to the final sample. Of the remaining children, 9509 had no psychiatric diagnosis, and 904 received another psychiatric diagnosis. For the purposes of this analysis, the children with OCD are compared with the normal controls and a psychiatric control group consisting of 421 children with emotional disorders, some of whom also had an additional non-emotional disorder such as a conduct disorder.
Prevalence, age and gender
Of the 10 438 subjects included in the survey, 25 children received a
diagnosis of OCD. After weighting the sample for differential response, this
gives an overall prevalence of 0.25% (95% CI 0.14-0.35). Although overall
numbers are small, dividing OCD cases into the age bands shown in
Table 2 reveals an exponential
increase in the rate of OCD as age increases
(Fig. 1). Diagnoses in the
under-11s are based on parental accounts and in the over-11s on a self-report
and parental report, but the increase with age is not accounted for simply by
a jump in prevalence after the age of 11 years, when self-report is included.
The increase with age is just as evident when the number of informants does
not change (from 5-7 to 8-10 years or from 11-12 to 13-15 years). Prevalence
rates for the different age bands are as follows: 5-7 years, 0.026% (95% CI
0.00-0.08); 8-10 years, 0.14% (95% CI 0.002-0.28); 11-12 years, 0.21% (95% CI
0.004-0.41); 13-15 years, 0.63% (95% CI 0.30-0.95). There were equal numbers
of boys (13) and girls (12) with OCD overall.
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The characteristics of the 25 children with OCD are summarised in
Table 2, compared with normal
controls (n=9509) and the group with emotional disorders other than
OCD (n=421). There was a significant difference
(P<0.0001) in age distribution between the three groups, the OCD
group being older, with 16 individuals aged 13 years or older and only one
aged less than 8 years. The OCD cases were significantly older than both the
normal controls (2=22.8; d.f.=3; P<0.001) and the
psychiatric controls (
2=8.8; d.f.=3; P=0.03). The
mean age of the OCD cases is 12.6 years (s.d.=2.2; range=7-15).
Correlates
Social class distribution (see Table
2) differed between the three groups (P<0.0001).
Compared with normal controls, the social class of the OCD sample was
significantly lower, with 74% being in the lower social classes compared with
47% of the normal controls (2=6.9; d.f.=1; P=0.009).
When the OCD group was compared with the psychiatric controls, a similar shift
towards lower social classes was found (
2=3.4; d.f.=1;
P=0.66). Family size differed across the three groups
(P<0.002); children with OCD came from larger families than normal
controls (
2=11.1; d.f.=3; P=0.011), with a similar
trend when compared with the psychiatric controls (
2=7.0;
d.f.=3; P=0.073). Income levels also differed significantly between
the three groups. Families of children with OCD had significantly lower
incomes than normal controls (
2=9.5; d.f.=3; P=0.023)
but income was not different from that found in psychiatric controls
(
2=2.2; d.f.=3; NS). In summary, OCD occurred equally often in
boys and girls, but those with OCD differed from the other children in tending
to be older and from larger families. Their families also tended to be of
lower social class and to have lower average incomes.
There was a significantly greater proportion of children from ethnic minorities in the OCD sample compared with the normal controls or the psychiatric controls (P=0.019).
The mean BPVS IQ of the 25 OCD cases was 87.4 (s.d.=15.3; range=65-120). This compares with a mean IQ of 95.7 in the emotional disorder control group and 101.8 in the normal controls. The OCD group was significantly lower than the normal controls (t=4.69; P<0.001) and the psychiatric control group (t=2.26; P=0.025). Within the OCD group further analysis was carried out, comparing those with and without comorbid conduct disorder and those from low and high socio-economic class. Low IQ was not accounted for by either of these variables. Only 1/25 cases had a specific learning disability (ability-attainment discrepancy in the lowest 5%).
Comorbidity
Comorbid diagnoses were found in 19 cases (76%), both using ICD10
and DSMIV comorbid definitions. Using ICD there were 10 subjects (40%)
with two or more diagnoses; the corresponding figure using DSMIV was 11
subjects (44%). Using ICD10, the types of comorbid diagnoses were: 13
with anxiety disorders (52%), 5 with depression (20%), 11 with conduct
disorder (44%) and 1 with an eating disorder (4%). An examination of the 11
cases with a broad conduct disorder diagnosis shows that 6 had oppositional
defiant disorder, 3 had socialised conduct disorder and 2 had other forms of
conduct disorder. There were no children with comorbid hyperactivity or tic
disorders.
Impact of OCD and service use
The impact scores of the parent SDQ (five items; range 0-10) and of the
teacher SDQ (three items; range 0-6) were used to assess overall impairment in
the child's functioning (Table
3). Impact scores for all informants were significantly higher in
children with OCD than in normal control children. Parents and teachers of
children with other emotional disorders rated them as presenting a similarly
high impact as children with OCD. Children with OCD did not rate their own
impairment significantly differently from the ratings given by children in the
psychiatric control group. Self-report scores on the GHQ showed similar levels
of psychological distress in parents of children with OCD and with other
non-OCD diagnoses.
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Previous contact with services also was examined. At some stage in the history of their child's difficulties, 36% of the families of children with OCD had consulted their general practitioner, either for OCD or for a comorbid emotional or behavioural problem. The corresponding rates of consultation were 12% for child specialist services (paediatricians or child mental health services), 8% for social services, 20% for educational services and 0% for alternative therapies.
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DISCUSSION |
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Our finding of equal rates in boys and girls is consistent with most epidemiological studies of this age group (Flament et al, 1988), although clinical samples frequently have contained more boys than girls. By age 18 years a female predominance is reported in epidemiological samples (59.55% in Douglass et al, 1995) and this is the case for most adult studies.
The trend towards higher rates of OCD in the ethnic minority groups reported here is in contrast to previous findings in epidemiological samples. Other studies have suggested that OCD is relatively rare in non-White populations, although this might not be specific to OCD, because rates for other psychiatric disorders appeared low (Karno et al, 1988).
Social class and intelligence
Most previous epidemiological studies would have been unable to detect
ethnic or socio-economic trends because the samples usually have consisted of
rather homogeneous populations, unlike the nationwide sample reported in the
present study. The sample surveyed here shows a trend for higher rates of OCD
in lower socio-economic groups, in line with most other psychiatric disorders
detected in the survey. This is in contrast with the findings of Flament
et al (1988), who
found no correlation with socio-economic status. Clinical samples consistently
have shown the reverse trend (Hanna,
1995), and the belief that OCD is a disorder of children of high
social class seems quite widespread but probably represents an artefact of
clinic populations.
The present study shows that the individuals with OCD had significantly lower IQs than normal controls. Few epidemiological studies have included measures of cognitive functioning, so it is difficult to compare the finding reported here with other samples. In a study of young Israeli army recruits, similar findings are reported for individuals with OCD compared with normal controls (Zohar et al, 1993). Another study failed to show any difference in cognitive profile between young individuals with OCD and psychiatric or normal controls (Douglass et al, 1995). Several studies have reported school difficulties in young people with OCD, including higher rates of significant specific learning disability, that appear to predate the onset of OCD (Swedo et al, 1989; Hanna, 1995). Once again, this finding of lower IQs in individuals with OCD is in contrast to the beliefs stated in much of the early anecdotal literature, where it is held generally that people with OCD are of above average intelligence (reviewed by Rasmussen & Eisen, 1998).
Comorbidity
The high rates of comorbidity reported here are in line with the rates from
other epidemiological samples, showing that about two-thirds of young people
with OCD have at least one other psychiatric diagnosis (reviewed by
Zohar, 1999). Several clinical
studies report rates of about 20% for comorbid tic disorders, but this was not
found in our sample, nor in most other epidemiological samples
(Flament et al, 1988;
Douglass et al, 1995). One epidemiological study that included specific screening questionnaires for
tics did report higher than expected rates of tic disorder
(Zohar et al,
1992).
This high rate of comorbidity, the often chronic nature of OCD itself and the associated disadvantages may contribute to the high levels of impairment experienced by young people with OCD. There is a clinical suggestion that early detection and treatment can improve prognosis (Leonard et al, 1993), yet the majority of children identified in this survey were unknown to services despite the availability of safe and effective treatments (Rapoport & Inoff-Germain, 2000).
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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Received for publication December 15, 2000. Revision received April 11, 2001. Accepted for publication April 11, 2001.
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