Department of Psychiatry and Behavioural Sciences, Royal Free and University College Medical School, London
Department of Psychiatry and Neuropsychology, Maastricht University, The Netherlands
Department of Psychiatry, Institute of Psychiatry, London
The John Howard Centre, London
Fromeside Clinic, Bristol
Department of Psychiatry, Institute of Psychiatry, London
the UK700 GROUP
Correspondence: Dr Kwame McKenzie, Department of Psychiatry and Behavioural Sciences, Royal Free and University College Medical School, Royal Free Campus, Rowland Hill Street, London NW3 2PF,UK
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ABSTRACT |
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Aims To compare rates of suicidal behaviour in people of Caribbean and British White origin in a large multi-centre sample of patients with psychosis.
Method A secondary analysis of 708 patients with psychosis followed up for 2 years. Outcome measures of reported suicide and attempted suicide were adjusted for socio-economic and clinical differences between groups at baseline.
Results People of Caribbean origin had a lower risk of suicidal behaviour than British Whites (odds ratio adjusted for age and gender 0.49, 95% CI 0.260.92). There was a strong negative interaction between ethnic group and age: suicidal acts were four times less likely in people of Caribbean origin aged over 35 years compared with British Whites, but there was no large or significant difference in those under 35.
Conclusions The previously reported lower relative risk of suicidal behaviour in people of Caribbean origin with psychosis is restricted to those over 35 years, suggesting that the protective effect of Caribbean origin is disappearing in younger generations.
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INTRODUCTION |
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METHOD |
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Data collection
The rationale for the study, the baseline characteristics of the study
group and the outcome of the case management trial have been reported
elsewhere (Burns et al,
1999; Creed et al,
1999). In brief, patients with research diagnostic criteria
(RDC)-defined psychosis (Spitzer et
al, 1978) aged 1865 years who had been admitted at
least twice to a psychiatric hospital were enrolled in a randomised controlled
trial of intensive case management between February 1994 and April 1996.
Demographic and socio-economic information was documented at baseline. Diagnoses were made using the Operational Criteria Checklist for Psychotic Illness assessment (McGuffin et al, 1991) from patient notes and from a semi-structured mental state examination performed for completion of the Comprehensive Psychopathological Rating Scale (Jacobsson et al, 1978), which includes the Montgomery and Åsberg Depression Rating Scale (MADRS; Montgomery & Åsberg, 1979). Clinical history was assessed using the World Health Organization (WHO) Life Chart (World Health Organization, 1992).
Ethnicity
Ethnicity was assigned by observers, according to Office of Population
Censuses and Surveys (OPCS) ethnicity categories
(OPCS & General Register Office for
Scotland, 1992). This was supplemented by information on
patients and patients parents place of birth. The aim was
to produce a group of Caribbean origin and, for comparison, as homogeneous a
British White group as possible.
The OPCS census White category can include people from a variety of countries. The largest minority ethnic group, the Irish, are usually subsumed in this group but they may have different mental health needs to those born in the UK of British parents (Littlewood & Lipsedge, 1997). This can make explanations of any differences between groups difficult. In this study, White British=OPCS category White with mother and father born in the UK.
Patients of Caribbean origin are also a heterogeneous group. However, this group has shared histories, reasons for migration, concentrations in certain geographical areas of the UK and shared experiences of discrimination. These may produce similarities in their needs and experience of services. In this study, Caribbean origin=OPCS category BlackCaribbean or Black Other with mother or father born in the Caribbean or UK.
Follow-up
Stratified randomisation ensured that equal proportions of White British
and Caribbean origin patients were allocated to each treatment arm. Patients
were followed up for an average of 2 years from the time they were randomised.
They were re-interviewed at 1 and 2 years and all the instruments used at
baseline were repeated. Here we present data for the 2-year follow-up.
Follow-up interviews were undertaken by independent researchers not involved in patient care. Patients and, when available, relatives and carers were interviewed. Each patients case manager was interviewed. Other mental health professionals involved in the case were interviewed. Patients case notes were also reviewed. The aim was to construct as accurate a picture as possible of the course of the illness, admissions and treatment.
Measurement of suicide and suicide attempts
The main outcome variable was suicidal behaviour (attempted or completed
suicide) between the baseline and 2-year follow-up interviews
(Walsh et al, 2001).
In the WHO Life Chart interview (World
Health Organization, 1992), individuals were asked whether they
had attempted suicide during this time and, if so, how often. A suicide
attempt was defined as a self-destructive act carried out with the intention
of ending ones life. Ratings were based not only on patient report but
also on all available sources of information, including case notes and
interviews with relatives and case managers. Where a 2-year outcome interview
with a subject was not possible, an attempt was made to complete the WHO Life
Chart using all other sources of information. Completed suicides were also
recorded at each centre.
Statistical analysis
Demographic and clinical differences between AfricanCaribbean and
White British patients were investigated in univariate analyses. Differences
between the two groups were considered significant at a level of
P<0.05. Possible explanatory variables for any difference were
decided a priori and included gender, age, education, diagnosis,
MADRS score and length of illness.
The 2-year relative risk of suicidal behaviour (suicide and suicide attempts) was calculated in the total sample and comparisons were made between the two ethnic groups using the chi-squared test initially for binary variables. Logistic regression analysis yielding odds ratios (ORs) was subsequently used to assess the effects on suicidal behaviour or demographic and clinical differences between the groups. Models included age, RDC diagnosis, educational level, MADRS score and time from onset of psychosis to study entry.
In order to test whether any association between suicide and ethnicity varied as a function of age, age by ethnicity interactions were added to the logistic regression model and assessed by the likelihood ratio test. A sensitivity analysis was conducted to assess the possible effect of differential drop-out.
We had conceptualised suicide and suicide attempts as one type of behaviour (Walsh et al, 2001) but accept contrary views that there may be differences between those who complete suicide and those who attempt suicide; therefore, for completeness, we repeated the analysis excluding those who had completed suicide.
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RESULTS |
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Sources of information
There was no difference between the groups in the mean number of sources of
information (patient, carers, relatives, mental health professionals, case
notes, others) used to complete the interview schedule at baseline (Caribbean
origin 2.6; White British 2.6) or follow-up (Caribbean origin 2.6; White
British 2.7).
A total of 26 patients of Caribbean origin (13%) and 35 White British (15%) were not interviewed at follow-up. There were no differences between the groups in the proportions of patients who refused interview or the reasons for non-interview. The most common reason for non-interview was refusal: 25 patients refused to be interviewed (6.5% of Caribbean origin and 5.5% White British). There was no difference between the groups in the mean number of sources of information that were used for those patients who were not interviewed at follow-up (Caribbean origin 2.0; White British 1.8).
Patients who dropped out of the study
A total of 45 patients dropped out of the study (20 of Caribbean origin, 25
White British). There was no difference between those of Caribbean origin and
the White British in the rate of drop-out from the study. For those who
dropped out there were no group differences in gender, mean age, educational
level, diagnosis, depression score or duration of illness as measured by
months between first onset of psychosis and study entry. Among those who
dropped out, more White British were recorded as having attempted suicide in
the 2 years before entry to the study (7 White British, 1 of Caribbean origin;
P=0.05).
Length of follow-up
Patients were followed up, on average, for 24 months and over 50% of
patients were interviewed within 1 month of their 2-year interview date. There
was no difference between the groups in the proportions of patients
interviewed early, late or on time.
Effect of ethnic group
There was no significant difference in the number of completed suicides
between the groups (31.5% of Caribbean origin and 41.7% White British).
People of Caribbean origin had a lower (albeit statistically imprecise) risk of performing, on at least one occasion, a suicidal act over the follow-up period: 17 (8.4%) of the Caribbean origin group and 33 (14.7%) of the White British group (OR=0.56, 95% CI 0.301.03; P=0.063). After adjustment for age and gender, this difference was increased rather than decreased (OR=0.49, 95% CI 0.260.92; P=0.025). Additional adjustment for RDC diagnosis (four categories: schizophrenia; schizoaffective psychosis; affective psychosis; other psychosis), chronicity (defined as months from onset of psychotic symptoms to study entry), level of education (in three levels: no qualifications; CSE/GCSE/GCE O-levels; A-levels/degree) and MADRS depression score increased the odds ratio by only a slight amount compared with the unadjusted odds ratio (OR=0.59, 95% CI 0.301.14; P=0.12). An analysis performed by excluding those who had died by suicide produced similar results (see Table 2).
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Age by ethnic group interaction
There was a strong negative interaction between age and ethnic group
(unadjusted model: likelihood ratio statistic (LRS)=6.8, 6.8, d.f.=1,
P=0.0093; model adjusted for gender, diagnosis, educational level and
chronicity: LRS=6.7, d.f.=0.0097). Stratified analyses revealed that there was
no significant difference between the groups in the number of people who
performed at least one suicidal act in those aged under 35 years (14/89
Caribbean origin patients (15.7%) and 14/67 White British patients (20.8%);
P=0.54) but there was a significant difference in those aged over 35
years (3/94 Caribbean origin patients (3.2%) and 19/142 White British patients
(13.4%); P=0.01). Thus, in the group aged 35 years and older,
Caribbean ethnic group was associated with a significantly lower risk (OR
adjusted for all confounders, including age in years=0.26, 95% CI
0.070.93), whereas there was no large or significant protective effect
in the group aged under 35 years (adjusted OR=0.92, 95% CI
0.382.20).
Analysis by excluding completed suicides produced similar results (see Table 2): LRS=6.52, d.f. 1, P=0.012.
Sensitivity analyses
Previous suicide attempts are a predictor of future suicide attempts. Given
the positive association between ethnic minority group and previous suicide in
those who dropped out of the study, an attempt was made to assess the possible
impact on the results of those who dropped out. It was assumed that all of
those who dropped out of the study who had a past history of suicide attempts
would have attempted suicide in the follow-up period even if we had been
unable to find data to support this. The data-set was modified to reflect this
assumption and the regression analyses were re-run. For the whole group there
was a significant difference between those of Caribbean origin and White
British (OR=0.52, 95% CI 0.270.99). There was no significant difference
between those of Caribbean origin and White British in those under 35 years of
age (OR=0.72, 95% CI 0.321.64) but significant differences were found
between patients of Caribbean origin and White British patients in the rates
of suicidal behaviour in those over 35 years of age (OR=0.24, 95% CI
0.070.85).
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DISCUSSION |
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However, the study is a secondary analysis of UK700 data and so was limited in its ability to test hypotheses. The UK700 study was powered to investigate the impact of case management on the outcome of illness but suicide was not one of the primary outcome variables. Subsequent work demonstrated that the predictors of suicide and attempted suicide in the study were similar and this led to the use of the term suicidal behaviour and analyses in which suicide and attempted suicide have been treated as a continuum. Here, analysis of those who attempt but do not complete suicide, either alone or in conjunction with those who complete suicide, does not significantly affect the result. Although there are differences in the risk factors for attempted suicide and completed suicide in the general population, these differences in risk factor profiles are not always found in patients with severe mental health problems (Walsh et al, 2001).
Sources of bias
The fact that subjects were asked to recall events over a 2-year period may
have introduced recall bias. If this recall bias was different for our ethnic
groups, the results could be an artefact of this process. However, recall bias
was minimised by the use of multiple data sources and the fact that clients
were seen regularly because they were taking part in a case management
study.
It could be argued that, despite this, there could still be bias. For instance, the fact that people of Caribbean origin are known to be harder to engage could have led to biased assessments of suicide attempts. Clinical teams may have been more likely to miss suicide attempts in this group. However, this would not explain our findings, because younger people of Caribbean origin are considered more difficult to engage than older patients but there was no difference between their rates of suicidal behaviour and those of the White British group.
Bias in reporting could have been due to differences within the Caribbean origin group. Older people of Caribbean origin may have had as many suicidal acts but may have been less likely to admit to it. We could not exclude this possibility but we would have expected it to be minimised by close follow-up during the study.
Generalisability of results
This study could be criticised and its results said not to be generalisable
as patients may have received better care than usual because they were taking
part in a case management trial. Although this could have decreased
differences between ethnic groups it is not clear how it would have led to the
age differential in relative risk of suicidal behaviour reported here.
Generalisability could be questioned because all the centres were in the inner
city. However, the vast majority of patients of Caribbean origin live in
inner-city areas (Nazroo,
1997) and the majority of those with psychosis are likely to live
in such areas.
Data collection could be criticised because observers (caseworkers, carers and relatives) were not blind to the ethnicity of patients. We cannot exclude this source of bias but none of the assessors was part of the team that envisioned this analysis and none was aware that data from the study were to be pooled to investigate rates of suicidal behaviour in ethnic groups.
Reasons for the differences
The results of the study reflect findings from the general population where
the rate of suicide in younger people of Caribbean origin is climbing while
older people of Caribbean origin remain at lower risk than their White British
peers (Soni-Raleigh, 1996).
There has been no specific research to investigate this phenomenon but there
have been a number of hypotheses that attempt to explain it. It has been
claimed that changes in suicide rates may be due to decreased religious
affiliation. However, it is unclear whether the change in religious beliefs
between younger and older people of Caribbean origin is greater than that
between younger and older British Whites.
Selection for migration could be important. Older people of Caribbean origin who decided to make the journey to the UK may be more able to cope with the rigours of being a minority in the UK than their children.
Community factors
There could also be an effect of community. Older people of Caribbean
origin are more likely to stay living within their community. The loss of
support of the community or the higher exposure/loss of protection from
discrimination faced by younger people of Caribbean origin who move away from
their communities and into more diverse occupational and residential areas
could be important. Neeleman has shown a relationship between the density of
people of Caribbean origin in an area and their rates of suicide and
presentation to accident and emergency departments with suicide attempts
(Neeleman & Wessely, 1999; Neeleman et al,
2001). The rates of birth are higher from areas where they are
more in the minority. There is a doseresponse relationship but the
relationship is complex and influenced by social class. Our sample of patients
were nearly all unemployed, on Government support and concentrated in social
housing in poorer inner-city wards. Because of this residential concentration,
simple ethnic density effects are unlikely to explain our findings.
There is some evidence from the USA that patterns of suicide in minority groups change between the first and second generations. The second and subsequent generations seem to approximate better to the rates of the host population (US Department of Health and Human Services, 2001). It may well be that our findings reflect a cultural shift within those of Caribbean origin in the UK, with White British norms being taken up by younger members and solutions to difficulties in life, such as suicide, being seen as more acceptable to them.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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The UK700 Group is a collaborative study team involving four clinical centres. At the time of the study the group consisted of: Manchester Royal Infirmary: Tom Butler, Francis Creed, Janelle Fraser, Peter Huxley, Nicholas Tarrier and Theresa Tattan; Kings Hospital/Maudsley Hospital, London: Thomas Fahy, Catherine Gilvarry, Kwame McKenzie, Robin Murray, Jim Van Os and Elizabeth Walsh; St Marys Hospital/St Charles Hospital, London: John Green, Anna Higgitt, Elizabeth van Horn, Donal Leddy, Patricia Thornton and Peter Tyrer; St Georges Hospital, London: Robert Bale, Tom Burns, Matthew Fiander, Kate Harvey, Andy Kent and Chiara Samele; Centre for Health Economics, York: Sarah Byford and David Torgerson; London (Statistics): Simon Thompson (Royal Postgraduate Medical School) and Ian White (London School of Hygiene and Tropical Medicine).
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REFERENCES |
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Received for publication November 20, 2001. Revision received February 4, 2003. Accepted for publication February 19, 2003.
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