Lea Castle Centre, Kidderminster, Worcestershire
Janet Shaw Clinic, Birmingham
Section of Developmental Psychiatry, University of Cambridge
Department of Clinical Genetics, University of Birmingham, Birmingham
Correspondence: Dr David Clarke, Lea Castle Centre, Kidderminster, Worcestershire DY10 3PP, UK
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ABSTRACT |
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Aims To report the nature and prevalence of compulsive and similar symptoms associated with PraderWilli syndrome in a population ascertained as completely as possible.
Method Attempted complete ascertainment of people with PraderWilli syndrome in eight English counties. Administration of standardised rating scales and a structured interview. Comparison with people with learning disability and high body mass indices.
Results PraderWilli syndrome was associated with high rates of ritualistic behaviours, such as the need to ask or to tell something, insistence on routines, hoarding and ordering objects and repetitive actions and speech, compared with the control group, and was negatively correlated with IQ and socialisation age. Typical obsessivecompulsive symptoms, such as checking, counting and cleaning compulsions or obsessional thoughts, were not found.
Conclusions Ritualistic and compulsive behaviours occur more frequently in association with PraderWilli syndrome than among people with intellectual disability and significant obesity.
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INTRODUCTION |
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METHOD |
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Standard checklists of obsessive and compulsive symptoms were not used in this study in view of their lack of reliability and validity when used to assess people with intellectual disability. Some people with PWS included in the study had severe intellectual disability, making the assessment of aspects such as distress caused by OCD symptoms (required by most standardised checklists) almost impossible. Questions were asked in a semi-structured interview the PWS Structured Interview Questionnaire (PWSSIQ) developed specifically for this survey (further details available from the author upon request). The interview lasted between 2.5 and 4 h and was, conducted with the main carer of the person with PWS. Carers were encouraged to describe all behaviours that they perceived as problematic. The questionnaire included items relating to diagnosis based on the consensus clinical criteria published by Holm et al (1993), behavioural problems, eating behaviour (including hoarding of objects as well as food), childhood psychiatric disorders (attention-deficit, hyperactivity and autistic disorders), schooling, physical health and receipt of medication. Informant versions of the Developmental Behaviour Checklist (DBC; Einfeldt & Tonge, 1993), Aberrant Behaviour Checklist (ABC; Aman et al, 1985a,b) and Vineland Adaptive Behaviour Scales (VABS; Sparrow et al, 1984) were administered. Anecdotes and examples were sought and follow-up questions were used to clarify ambiguous statements. An appropriately trained investigator (J.W.) also spent time with the person with PWS and administered the appropriate Wechsler intelligence scales and tests of attainment in reading, spelling and arithmetic. This gave an opportunity to observe the person with PWS and his or her reactions to the test situation, and provided additional information about attention and concentration. In view of the eating disorder associated with PWS, repetitive, preoccupying thoughts relating to food have been excluded from the results presented; almost everyone with PWS who was seen seemed to spend a great deal of time thinking about food.
A comparison group has been used that consists of people with learning disability and people who had volunteered to take part in the epidemiological study but who were found on genetic or clinical grounds not to have PWS. Such a contrast group has the advantage of having similar overall severities of cognitive impairments and high body mass indices (see Table 1). The use of such a comparison group allows an estimate of the prevalence of obsessive and compulsive symptoms associated with PWS (rather than with obesity or intellectual disability). The same measures and assessments were used for the comparison group.
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The hypothesis that compulsive symptoms are associated with developmental delay, as suggested by Dykens et al (1996), would be consistent with an agerelated decline in such symptoms, or with a ceiling effect, such that development and compulsive symptoms stick at a stage of development that unaffected children pass through. This hypothesis was tested in the present study by correlating compulsive behaviours with chronological age, with IQ (as a measure of mental age) and with the VABS score (a measure of socialisation age).
Two measures of compulsive symptoms were formed: a simple count of the number of symptoms from the list in Table 2, plus needs routine and anticipation (endorsed by informants), and a weighted count in which those behaviours rated as a severe problem were given a count of 2 whereas those rated as a problem were given a count of 1. The sample was divided into the age bands 5-12 years, 13-19 years and 20 years and over. The IQ was defined as the fullscale score on the age-appropriate Wechsler ability test. Socialisation age was defined as the age-equivalent score on the VABS. Obesity was assessed using the body mass index (BMI: weight in kilograms divided by height in metres squared). For adults, the maximum BMI also was recorded, where known.
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Mood swings were assessed using the sums of scores of carer-rated items relating to mood swings ever on the PWSSIQ (rated 0-4) and the score on the ABC item mood changes rapidly (for adults) or the DBC item mood changes rapidly for no apparent reason (for children). Anxiety and depression were assessed by the sums of the scores for items ever had severe anxiety lasting more than a few days, ever had severe depression lasting more than a few days, ever had other nervous problem lasting more than a few days (all items from the PWSSIQ), exhibits excessive unhappiness (VABS) and depressed mood (ABC for adults, DBC for children). Autistic traits were assessed using the sum of the scores from six PWSSIQ items with the stem hardly ever: initiates conversation, calls attention to things, smiles in response, cooperates in play, makes eye contact, shows imaginative play and the items has repetitive talk and has little emotional expression.
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RESULTS |
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Compulsive symptoms did not decline with age in the PWS sample and were not correlated with obesity (BMI or maximum BMI), with (long-term) anxiety/depression or with severity of eating behaviour. The latter finding may mask a ceiling effect because all people with PWS have some problems with appetite regulation. There were significant positive correlations with (short-term) mood swings (r=0.23 and P=0.05 for weighted compulsion count) and autistic symptoms (r=0.52 and P < 0.001 for weighted compulsion count). There were significant negative correlations with IQ (r=-0.30 and P=0.008 for weighted count) and socialisation age (r=0.30 and P=0.002 for weighted count). An examination of correlations between weighted compulsion counts and IQ, socialisation age and autistic symptoms individually, controlling for the effect of the other two variables, showed no significant correlations other than for autistic symptoms (controlling for IQ and socialisation) (r=0.34, P=0.005). No significant correlations were found for the contrast group. Some stereotyped and ritualistic behaviours were seen during direct observation of the people with PWS who took part in the study. No tics were noted.
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DISCUSSION |
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Compulsive symptoms were found to be much more prevalent in our study groups of people with PWS than in the contrast group of people with similar severities of intellectual disability, who were of similar ages and who had high BMIs. It is, therefore, unlikely that the high rate of compulsive symptoms is accounted for by the relative obesity of many people with PWS or by the presence of intellectual disability. Taken with other information about the clinical features and behavioural characteristics of populations of people with PWS, there is some evidence for a constellation of features (labile mood, vulnerability to loss of temper, ritualistic and compulsive symptoms, repetitive questioning and insistence on routine) similar to the attributes of children without developmental disability in early childhood.
Dykens et al (1996) described 91 people with PWS, aged 5-47 years (mean=18 years), with IQs ranging from 50 to 89 (mean=69) who were recruited at PWS Association meetings and through support groups. The findings were compared with those for 43 people who did not have intellectual disability but did have a clinical diagnosis of OCD and were recruited from three clinics for people with OCD. The PWS group were rated using a modified (informant) version of the YaleBrown Obsessive Compulsive Scale (YBOCS; Goodman et al, 1989a,b), completed by their main carer; the OCD group completed the standard (self-report) version of the YBOCS. In both versions of the instrument, 56 symptoms were rated as being present in the past week or ever (analyses being based on the ratings for the past week). Ten additional items in the YBOCS rated symptom severity, including the extent to which symptoms were time-consuming, distressful, out of control or causing social or occupational impairment. Informants reported high rates in the PWS group of compulsions concerning hoarding (58%), a need to tell or ask (53%) and ordering, arranging and repeating rituals (37-38%). Other compulsions reported included cleaning (24%), counting (17%) and checking (15%). Obsessions also were reported, but these were less prevalent. Informants reported compulsive behaviours causing moderate or severe distress in 64% of people, adaptive impairments in 80% and excessive time consumption in 45%, using the Y-BOCS scaling. Comparisons with the OCD clinic sample indicated significant differences (P < 0.05) for two compulsions that were more common in the PWS group: hoarding (79% v. 7%) and needing to tell or ask (51% v. 23%). Checking behaviour was less common in the PWS group (16% v. 55%); all other ratings did not differ significantly between the two groups.
The authors concluded that increased risks of OCD are strongly indicated in people with PWS, based on the range and severity of symptoms encountered in this sample. They noted also that some diagnostic criteria for OCD, including DSMIV (American Psychiatric Association, 1994), do not include the criterion of the person's recognition that their symptoms are excessive or unreasonable in the case of children, and argued that people with PWS may have less insight into their OCD symptomatology because of their cognitive limitations. Dykens et al (1996) also noted that the pattern of symptoms they found to be associated with PWS loaded on only one factor (the principal factor) that emerged from a factor analysis of YBOCS ratings of 107 patients with OCD (Baer, 1993). This factor includes aspects such as hoarding, repeating rituals and concerns with symmetry, exactness, ordering and arranging. Feurer et al (1998) reported that analysis of the Compulsive Behavior Checklist (CBC) scores of people with PWS yielded only one general factor, with the exception of an item relating to deviant skin-groomingskin-picking.
Compulsive symptoms and child development
The prevalence of obsessional and compulsive symptoms varies throughout
childhood. Bedtime and dressing rituals are common in early childhood
(Gesell et al, 1974).
Other rituals and compulsive-like phenomena may occur later in childhood. The
prevalence of obsessional disorders, as distinct from compulsive acts, has
been estimated at between 0.2% and 12% of clinical populations of children and
adolescents (Judd, 1965;
Hollingsworth et al,
1980). Zohar & Bruno
(1997) studied 1083
schoolchildren aged 8-13 years in Jerusalem using the Maudsley
ObsessiveCompulsive Inventory
(Hodgson & Rachman, 1977).
They found that obsessional ideas and compulsive behaviours were common among
children at the age of 8 years, but were present in only a minority of
children aged 13 years. Evans et al
(1997) used the Child Routines
Inventory to assess compulsive-like behaviour in children and found that
children between 2 and 4 years of age had higher rates of such behaviours than
children aged below 1 year or above 4 years.
Goodman et al (1989a) reported the presenting symptoms among 70 consecutive children and adolescents with a primary diagnosis of OCD and found the most common obsessions to be those concerning contamination by dirt or germs (40%), worries about something terrible happening (24%) and worries about symmetry, order and exactness (17%). The most commonly reported compulsions were those concerning excessive or ritualised hand-washing, showering, bathing, tooth-brushing or grooming (85%), repeating rituals (e.g. going in and out of a door-way) (51%) and checking compulsions (46%). Compulsions regarding ordering or arranging were found in 17%, counting in 18% and hoarding or collecting in 6%.
These studies suggest a shift during childhood from relatively common rituals and compulsive-like behaviours in early childhood to low rates of obsessional and compulsive symptoms resembling those of adult OCD among vulnerable children later in childhood and in adolescence.
Serotonin and compulsive and ritualistic behaviours
Obsessivecompulsive symptoms or OCD may occur in the context of
depressive illness, and its response to antidepressants such as clomipramine
and specific serotonin reuptake inhibitors (SSRIs), as well as evidence from
neurochemical studies, suggests the involvement of the serotonergic system in
the genesis or maintenance of OCD (Goodman
et al, 1991; Riddle
et al, 1992; Zohar et al,
1987,
1988). Although abnormalities
in serotonergic systems seem to play a part in the genesis of some OCDs, it
seems likely that the anti-obsessional effect of drugs acting on serotonergic
systems may result from alterations in the balance between serotonin and other
neurotransmitters, or changes in receptor functioning
(Murphy et al, 1989).
One study has reported abnormal serotonin turnover associated with PWS, with
increased concentrations of serotonin metabolites in the cerebrospinal fluid
of children and adolescents with PWS compared with comparison groups
(Åkefeldt et al,
1998).
Oxytocin
Leckman et al
(1994) reported elevated
cerebrospinal fluid oxytocin concentrations in association with OCD in people
without intellectual disability. A reduction in the number of
oxytocin-containing neurons in the paraventricular nucleus of the hypothalamus
has been found in post-mortem studies of some people with PWS
(Swaab et al,
1995).
Genetics
PraderWilli syndrome is thought to result from genomic imprinting,
with the absence of the paternal contribution to genes in the q11q13 area of
chromosome 15. The finding of high rates of ritualistic behaviour, together
with other reports of psychiatric disorder associated with the syndrome, may
be of relevance to understanding the genetic and metabolic basis of such
disorders in the general population.
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Clinical Implications and Limitations |
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LIMITATIONS
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REFERENCES |
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Received for publication June 21, 2001. Revision received November 29, 2001. Accepted for publication December 3, 2001.
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