University College London Department of Psychiatry and Behavioural Sciences, Royal Free and University College Medical School
Institute of Psychiatry, London
Department of Psychiatry, University of Leicester, Leicester
Office for National Statistics, London
South London and Maudsley NHS Trust
WHO Collaborating Centre, Institute of Psychiatry, London
Division of Psychiatry, University of Bristol, Bristol
Office for National Statistics, London, UK
Correspondence: Professor Paul E. Bebbington, Department of Mental Health Sciences, 48 Riding House Street, London W1N 8EY, UK. Tel: +44 (0)20 7679 9465; e-mail: p.bebbington{at}ucl.ac.uk
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ABSTRACT |
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Aims To use data from the second British National Survey of Psychiatric Morbidity to examine associations between psychotic disorders and a number of early victimisation experiences.
Method Psychiatric disorders were identified through structured assessment of adults resident in private households in Britain (n=8580). Respondents were asked whether they had experienced selected events displayed on cards.
Results Compared with respondents with other psychiatric disorders or with none, the prevalence of every experience bar one was significantly elevated in those with definite or probable psychosis. The largest odds ratio was for sexual abuse. Controlling for depressed mood somewhat reduced the odds ratios for the individual experiences.
Conclusions In people with psychosis, there is a marked excess of victimising experiences, many of which will have occurred during childhood. This is suggestive of a social contribution to aetiology.
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INTRODUCTION |
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METHOD |
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Sample
The Royal Mails small-users Postcode Address File was used as the
sampling frame for the survey because of its good coverage of private
households in Great Britain. The postcode sectors were stratified within each
National Health Service region on the basis of socio-economic profile.
Initially, 438 postal sectors (the primary sampling units) were selected with
a probability proportional to size (i.e. the number of delivery points).
Postal sectors contain on average 2550 delivery points; 36 were selected from
each sector (with the exception of one sector that was accidentally sampled
twice), yielding a sample of 15 804 delivery points. These were visited to
identify private households with at least one person aged 1674 years.
The Kish grid method was used to select systematically one person in each
household (Kish, 1965).
Each interviewer was given 36 addresses to visit within a month. Letters were sent in advance to all addresses, giving information about the survey and advising the residents that an interviewer would be calling to tell them more about the survey and ask whether they would be willing to participate.
The selected adult in each household was asked to take part in an initial computer-assisted personal interview with an ONS interviewer. Questions about alcohol and drug dependence were answered by respondents themselves directly on the computer. All respondents who completed an initial interview were asked whether they would be willing to take part in a second phase. The second-phase sample was chosen to include:
Only those who agreed to being contacted for a second interview were included in the second phase.
Coverage of disorders
To test the first of our predictions, we compared individuals with a
psychotic disorder with respondents who had no disorder. To test the
specificity hypothesis, we used as comparison groups of people with
non-psychotic mental disorders and those with drug or alcohol dependence. All
diagnostic categories of mental disorder included in this paper were based on
the ICD10 (World Health
Organization, 1992). In order not to prejudice the results, the
diagnostic groups were established nonhierarchically: that is, individuals
were sometimes members of more than one diagnostic group. The comparison group
comprised respondents who fell into none of the chosen categories.
Alcohol dependence
Alcohol dependence was assessed using the Severity of Alcohol Dependence
Questionnaire (SADQ; Stockwell et
al, 1983). This consists of 20 questions covering symptoms of
dependence, and possible scores range from 0 to 3 on each question. Adding up
the scores from all questions gives a total SADQ score between 0 and 60,
indicating different levels of alcohol dependence. A score of 3 or less
indicates no dependence, mild dependence is indicated by a score of
419, moderate dependence by a score of 2034 and severe
dependence by a score of 3660. For the purposes of this paper, alcohol
dependence was defined as a score of 4 or more on the SADQ. The reference
period for the questions on alcohol dependence was the 6 months prior to
interview.
Drug dependence
A number of questions designed to assess drug use were included in the
questionnaire. Information was first obtained on all the types of drugs
respondents had ever used, and then about the drugs used in the year before
interview. Further information about drug use in the past year was collected
for cannabis, amphetamines, crack, cocaine, ecstasy, tranquillisers, opiates
and volatile substances (such as glue). This part of the survey included five
questions to evaluate drug dependence, which was indicated by a positive
response to any of them.
Common mental disorders
Non-psychotic psychiatric disorder was assessed using the Clinical
Interview Schedule Revised (CISR;
Lewis et al, 1992).
This can be administered by nonclinically trained interviewers, and training
was straightforward for the experienced ONS interviewers employed for the
survey. Moreover, the interview itself is relatively short (on average, 30
min) compared with other methods of assessment. Common mental disorders were
amalgamated into a single category, indicated by a total symptom score of 12
or over, assessed in relation to the previous week.
Detection of psychosis
A two-phase approach was adopted to assess the presence of psychotic
disorder. The Psychosis Screening Questionnaire
(Bebbington & Nayani, 1995) was administered at the first interview. The criteria from this interview
considered indicative of possible psychotic disorder were:
Meeting any one of these criteria led to selection for a second-phase interview using version 2.1 of the Schedule for Assessment in Neuropsychiatry (World Health Organization, 1999). A proportion of people who screened negative were also selected for the second phase. Some of the people selected for a second-phase interview refused, however, and some could not be contacted during the fieldwork period. For this study we defined a group of interviewees as having definite or probable psychotic disorder: definite disorder was that identified by the SCAN, whereas probable disorder was identified in those who had not had a SCAN interview but met two or more of the screening criteria described above. Endorsement of two or more items tallied closely with a positive diagnosis using SCAN in the Survey of Psychiatric Morbidity among Prisoners (Singleton et al, 1998). For brevity, these 60 respondents are described below as the psychosis group.
Selection and assessment of events
All respondents were shown three cards listing stressful life events, and
were asked to say which events, if any, they had experienced at any time of
their life. The first card included relationship problems, illness and
bereavement; the second, employment and financial crises; and the third,
victimisation experiences. All the events were ones that might have had an
adverse effect on the respondents mental health. Here we have chosen to
analyse the events that carried some connotation of victimisation: those
listed on the third card, plus having experienced assault, injury or serious
illness (Table 1). No attempt
was made to evaluate the severity of the experiences. Finally, respondents
were asked whether they had spent time in local authority care or in a
childrens institution before the age of 16 years.
Analysis
All analyses were performed using the relevant survey
commands in STATA 6.0 (StataCorp, 1999), which allow for the use of clustered
data modified by probability weights and provide robust estimates of variance.
We initially analysed the individual associations between events and
disorders, after which we controlled for the association between events in
their effects on the presence of psychosis by using logistic regression.
Finally, we examined the effect of controlling for the level of depressed
mood.
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RESULTS |
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In Table 1 we present the frequency of the various experiences in four case groups compared with respondents who were accorded no current diagnosis. For every experience, the prevalence was highest in the psychosis group, with the single exception of being expelled from school. These experiences were considerably less likely to be acknowledged by people who fell outside all the four case groups. We next provide the odds ratios for being in the different case groups, given a history of the various experiences (Table 2). This makes clear the increased risk of psychotic disorder in people with these experiences. The largest odds ratio was for sexual abuse, but it was followed closely by the experience of local authority care, residence in a childrens institution, running away from home and being homeless.
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Clearly, the odds ratios were very large. However, victimisation experiences may cluster in particular individuals, a relationship that might arise because of a clustering of disadvantage, because earlier events may predispose to later events, because early events interact with later events to increase the likelihood of psychosis or because of a reporting bias. It was therefore necessary to carry out a logistic regression in which the dependent variable was probable psychosis, and the experiences were entered together as independent variables. It is apparent from Table 3 that the reported events did indeed cluster in particular individuals: the significant odds ratios seen in Table 2 were much reduced. Although the largest odds ratio remained that associated with sexual abuse, some of the others were no longer significant (local authority care, bullying, violence at work) and the association with violence at home was only a non-significant trend. Childhood institutional care and local authority care overlap considerably, and it was unlikely that both would contribute significantly to the model. Controlling for the other experiences led to a significant inverse relationship with being expelled from school i.e. people with psychosis are significantly less likely than the unaffected population to report having been expelled.
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We repeated this analysis controlling for the key demographic variables of gender, age and ethnicity. We did not control for social class and educational attainment, as these are likely to be outcomes of the psychotic process. This analysis made remarkably little difference: the same event variables were required for the model of best fit. Finally, we took account of the possibility that the association of events with psychosis might better be explained by the effect of lowered mood. Lowered mood is common in psychosis, and the best-established links with events such as those we enquired about are with adult depression. We used the depression score on the CISR as a measure of lowered mood. As expected, this was strongly related to a study diagnosis of psychosis, to each of the victimisation events and to the experience of childrens institutions and local authority care (P<0.0001 in every case).
Although controlling for depressed mood did reduce the odds ratios for the individual events and experiences, in no case was a significant association rendered non-significant. For example, the odds ratio of psychosis in the face of sexual abuse fell only from 15.5 to 7.4. When we repeated the logistic analysis summarised in Table 3 with the additional entry of level of depressed mood, two circumstances ceased to contribute significantly to the model: being in a young persons institution and being homeless. The effects of controlling for mood are shown in Tables 4 and 5.
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DISCUSSION |
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Reportage probably also depends on the format of enquiry. Dill et al (1991) found that psychiatric patients were twice as likely to acknowledge histories of physical or sexual abuse in childhood in a confidential self-report survey as at the routine intake interview, although nearly all the events recorded at intake were endorsed in the later enquiry. There might thus have been advantage in our procedure of presenting cards with the relevant experiences, as this might have been perceived by respondents as less intrusive than cross-questioning. Despite this, the endorsement of (for example) the experience of sexual abuse by our total sample was, at around 4%, on the low side. We must ultimately acknowledge that validity remains insecure in studies such as this, and will be better dealt with through cohort studies.
There are other problems in interpreting our data. First, they relate to events occurring at an unspecified time in the respondents lives. The timing of some of the individual experiences is constrained in the question (e.g. local authority care before age 16 years or being in a childrens institution) and in other cases it can be inferred to some extent from their nature. Thus, being bullied is strongly a feature of school life, and even these days when bullying at work is more recognised, most respondents would imagine that the focus of the enquiry was the former. Running away from home is most likely to have occurred in adolescence. Violence in the home is quite likely to have been experienced in childhood, whereas violence at work would have occurred in adulthood. It might be expected that sexual abuse in people with psychiatric disorders is a childhood phenomenon (Friedman & Harrison, 1984; Palmer et al, 1993, 1994), although some authors have suggested that exposure to sexual victimisation in psychiatric patients is more common in adulthood (Coverdale & Turbott, 2000).
Ideally, we would have liked to explore the consequences of a model of psychosis in which early events contribute to vulnerability but the psychosis itself is triggered by later events. However, the timing of events was insufficiently demarcated to allow this.
Confirmation of predictions
Our first prediction was confirmed: all but one of the experiences we
selected for analysis were reported significantly more frequently by the group
of people with psychotic disorders than by those with no psychiatric problem.
Our second prediction concerning the lack of specificity was also generally
confirmed. People with common mental disorders, alcohol dependence or drug
dependence also had high rates of reporting victimisation experiences.
However, in each case the relative odds were highest in the psychosis group,
with one interesting exception: a history of being expelled from school was
not more frequent in the psychosis group than in the normal control group,
whereas it was reported considerably more often in the alcohol-dependent
group, and was particularly frequent in drug-dependent respondents. Being
expelled involves the response of school authorities to unacceptable
behaviour, usually of a flagrant kind. The distribution of expulsion between
the groups of disorders suggests that the people with psychosis might have
been socially reticent in adolescence, in contrast to the early acting-out
behaviour of those with drug and alcohol misuse problems.
Some of the recorded experiences depended to a major extent on the actions of others (local authority care), whereas the contribution of respondents to other events is more central, for instance running away from home. Thus, we can infer no simple causal direction.
Vulnerability to an increased event rate
The results are also consistent with other possibilities, such as
vulnerability to the unwelcome attention of others. This vulnerability may
itself arise from prior social experience, or from attributes related to a
genetic or other biological predisposition to psychosis. Goodman et
al (1997) in their review
paper found high rates of sexual victimisation in women with schizophrenia,
including in adulthood. They did not postulate an effect of childhood abuse on
schizophrenia, but rather concluded that the nature of the disorder left
patients more vulnerable to abuse.
Given the cognitive and social deficits in some children who subsequently develop schizophrenia, they may be especially targeted by abusers because they are less likely to tell, are more easily intimidated or have greater difficulty in confiding in adults. Lysaker et al (2001a, b) found that self-reported childhood sexual abuse in people with schizophreniform disorders is linked to an increased severity of neurocognitive deficits and a reduction in psychosocial functioning. Done et al (1994) used a cohort study, the British National Child Development Study, to show that children who later developed schizophrenia had been rated as manifesting more social maladjustment at the age of 7 years than controls, especially in relation to overreactive behaviour. Bergman et al (1997) found that maltreated children had poorer neuromotor functioning and significantly more behaviour problems than non-maltreated children, regardless of parental psychiatric status. Put together, these studies suggest that maltreatment might influence the development of schizophrenia, but equally that behavioural oddities might lead both to maltreatment and to schizophrenia.
Effect of shared genes
Victimisation experiences may also cluster in individuals because of a
spurious association brought about by the genetic relationship between parent
and child. Child sexual abuse is associated with parental mental illness, with
a two-to-three-fold increase in the offspring of parents who have
schizophrenia compared with the general population
(Walsh et al, 2002).
However, most child sexual abuse is not perpetrated by the childs
biological parents.
Susceptibility to experiences
A tendency to be victimised does not in itself reduce the impact on the
individual experiencing victimisation, and the scene may then be set for a
malignant spiral. Although the impact of sexual abuse in people who later
develop depression may be mitigated by access to confiding adult relationships
(Hill et al, 2001), such access may be less available to people with psychosis, and this in turn
may increase their susceptibility to the impact of the events.
Some of the experiences covered by the rubrics used in our study are likely to be seriously traumatising, and raise the question of the relationship between psychosis and post-traumatic stress disorder (Bebbington & Kuipers, 2003). Mueser et al (1998) found rates of 43% for post-traumatic stress disorder among 275 psychiatric patients with severe mental illness, the disorder being strongly predicted by multiple traumas and childhood sexual abuse. However, rates were lowest in schizophrenia and schizoaffective disorders.
Other studies of early trauma in psychosis
There are few studies of early sexual abuse in schizophrenia: they are
small and methodologically limited. Friedman & Harrison
(1984) compared 20 women
in-patients with schizophrenia with 15 controls recruited by anonymous
questionnaires sent to female hospital employees. Sixty per cent of the
patients acknowledged sexual abuse (i.e. rape or being fondled against their
will) compared with 13.4% of controls. For most participants the abuse
occurred in childhood, but no details are given. Nettelbladt et al
(1996) reported significantly
increased rates of sexual encroachment (involving physical
contact, a perpetrator and clear evidence of coercion) before age 18 years
among 17 patients with schizoaffective disorder compared with controls. It
remains possible that the experience of childhood sexual abuse is linked to
adult psychosis because it is a marker for social poverty. Nelson et
al (2002) have provided
evidence that childhood sexual abuse is associated with a cluster of other
adverse family factors.
Mood as a mediator
We considered whether the mediating factor might be depressed mood, and
including this in the model did attenuate the relationships somewhat.
Nevertheless, independent relationships between our chosen experiences and
psychosis remained. Indeed, depressed mood is such a common correlate of
schizophrenic symptoms that it is now hypothesised as being an important part
of the process of their development
(Birchwood & Iqbal,
1998).
Significance of victimisation experiences
There is marked clustering of experiences that can be generally described
as victimising in people who are identified as probably having a psychotic
disorder. These experiences are spread throughout the age span, but include
those likely to have occurred during childhood, probably before the onset of
the psychotic illness. We cannot rule out the possibility that they occurred
in the context of early oddities of behaviour that might have been prodromal
to the disorder. Nevertheless, the sheer burden of these experiences in people
with psychosis is impressive, and at least suggests a process involving social
influences. The research in this area is limited and should be augmented by
work involving the more precise dating and characterisation of experiences.
Ideally, this should include cohort studies.
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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 August 21, 2003. Revision received February 16, 2004. Accepted for publication March 9, 2004.
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