Centre for Research on Drugs and Health Behaviour/Department of Social Science and Medicine, Imperial College London
Department of Psychological Medicine, Imperial College London
Division of Psychiatry, University of Nottingham
Nottinghamshire Healthcare NHS Trust
Department of Metabolic Medicine, Imperial College London
Central and North West London Mental Health NHS Trust, London
Community Health Sheffield NHS Trust
Turning Point, Brent, UK
Comorbidity of Substance Misuse and Mental Illness Collaborative (COSMIC) study team
Correspondence: Tim Weaver, Department of Social Science and Medicine, Imperial College London, Charing Cross Campus, The Reynolds Building, St Dunstans Road, London W6 8RP, UK. Tel: 020 7594 0863; fax: 020 7594 0866; e-mail: t.weaver{at}imperial.ac.uk
Declaration of interest None. Funding detailed in Acknowledgements.
* Peer-review and acceptance of this paper took place before P.T. became
Editor.
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ABSTRACT |
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Aims To measure the prevalence of comorbidity among patients of community mental health teams (CMHTs) and substance misuse services, and to assess the potential for joint management.
Method Cross-sectional prevalence surveyin four urban UK centres.
Results Of CMHT patients, 44% (95% CI 38.149.9) reported past-year problem drug use and/or harmful alcohol use; 75% (95% CI 68.280.2) of drug service and 85% of alcohol service patients (95% CI 74.293.1) had a past-year psychiatric disorder. Most comorbidity patients appear ineligible for cross-referral between services. Large proportions are not identified by services and receive no specialist intervention.
Conclusions Comorbidity is highly prevalent in CMHT, drug and alcohol treatment populations, but may be difficult to manage by cross-referral psychiatric and substance misuse services as currently configured and resourced.
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INTRODUCTION |
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METHOD |
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Design and setting
We conducted a cross-sectional prevalence survey between January 2001 and
February 2002 in four urban UK centres. These were two neighbouring
inner-London boroughs (Brent, and Hammersmith and Fulham) and services in
inner-city areas of Nottingham and Sheffield. At all four centres the CMHTs
were consultant-led, multi-disciplinary teams serving geographically defined
catchment areas. Each had access to designated in-patient beds, operated
according to contemporary care programme approach (CPA) guidelines and gave
priority (in terms of the allocation of case-load places) to patients with
severe and enduring mental illness. The drug and alcohol teams were statutory
providers. They offered separate structured, appointment-based services
through keyworkers within nurse-led clinics. All clients were allocated a
personal keyworker and assigned to the case-load of a psychiatrist or
responsible medical officer (RMO). All drug services had a strong emphasis
upon the management of opiate dependency. Independent drug services were
available in some areas (including services for stimulant users), but not in
others. These latter agencies were not investigated. In each population, we
completed a case-load census to identify the sampling frame and a patient
interview survey with case-note audit in a random sample.
Participants
All patients of the drug and alcohol teams who were allocated to the
case-load of a keyworker and psychiatrist/RMO on the census date were included
in the substance misuse case-load census population. The only current patients
excluded were a small proportion who had not completed an assessment. The
sample sizes were proportionate to the size of the total treatment populations
in each centre. To be included in the CMHT case-load census population,
patients had to be allocated to the case-load of a care coordinator and
psychiatrist/RMO on the census date, be aged 1664 years and be included
on the local CPA register. Only a small proportion of current CMHT patients
were excluded because they had not completed an assessment, or exceeded the
age range. Interview samples of 400 CMHT and 353 substance misuse patients
were selected from these census populations at the coordinating centre
(Imperial College) using Statistical Package for the Social Sciences (SPSS)
random case selection procedures (SPSS,
1999).
Data collection
Data collection procedures were agreed with local research ethics
committees. Services identified eligible patients, who were allocated
anonymous case numbers used in all data collection. Care coordinators and
keyworkers completed census questionnaires (one per patient), gave patients
sampled for interview an information sheet, and invited them to meet a trained
fieldworker. All interviewed patients gave written informed consent.
Non-consenting patients were regarded as non-respondents and not
substituted.
Assessments
Case-load census
Care coordinators and keyworkers were asked to report demographic details,
ICD10 psychiatric diagnoses (World
Health Organization, 1992) established or confirmed by psychiatric
assessment in the past year, and any psychiatric and substance misuse
interventions provided in the past month. Care coordinators for CMHT patients
were asked to identify people using any illicit or non-prescribed drug in the
past year, and to apply diagnostic criteria (reproduced on the census form) to
this group to identify those misusing drugs
(American Psychiatric Association,
1994). Care coordinators applied the same criteria to all patients
to identify those misusing alcohol.
Interview survey
Mental health status was assessed using the Quick Personality Assessment
Schedule (Tyrer, 2000), the
Comprehensive Psychopathological Rating Scale (CPRS;
Åsberg et al,
1978) and its sub-scales for rating depression
(MontgomeryÅsberg Depression Rating Scale;
Montgomery & Åsberg,
1979) and anxiety disorders (Brief Scale for Anxiety;
Tyrer et al, 1984).
All of the above assessments were applied to participants from both CMHT and
substance misuse patient populations. Research psychiatrists assessed patients
in the substance misuse group for psychosis using the Operational Checklist
for Psychiatric Disorders (OPCRIT;
McGuffin et al, 1991)
based on a case-note review. A specificity analysis was completed using
information from the patient interview to ensure conservative rating of
psychosis.
We used service-defined diagnoses to identify CMHT patients with psychosis.
We completed OPCRIT assessments in a subsample of cases, enabling a
specificity analysis to be completed; this showed that service-defined
diagnosis was acceptable and reliable in identifying people with psychotic
disorders (sensitivity 95%, specificity 81%). In our analysis the diagnostic
category psychosis included schizophrenia (F20.0F20.9);
schizotypal, schizoaffective, delusional and other unspecified psychotic
disorders (F21F29); manic episode with psychotic symptoms (F30.2);
bipolar affective disorder (F31); severe depression with psychotic disorder
(F32.3); and recurrent severe depression with psychotic symptoms (F33.3). The
Alcohol Use Disorders Identification Test (AUDIT;
Saunders et al, 1993)
identified harmful (score 8) and severe (score
15) alcohol-related
problems. A structured interview checklist identified drug types used (ever,
past year, past month) and whether associated problems were present (economic,
domestic, social, legal or interpersonal). Problem drug use was defined as
self-reported presence of one or more of the above drug-related problems or
care coordinator assessment of misuse. The Severity of Dependence Scale
(Gossop et al, 1995)
assessed drug dependency. These assessments were implemented in each treatment
population.
To assess the reliability of self-reported drug use in CMHT patients we tested hair and urine samples, obtained from a random subsample of participants, by means of chromatography (Paterson et al, 2000) and mass spectrometry analysis (Paterson et al, 2001). Samples were obtained contemporaneously with self-report data. However, consent for hair and urine testing was obtained separately after each interview assessment.
Analysis
All analysis presented in this paper was undertaken with the interview
samples achieved in each treatment population
(Fig. 1). The primary analysis
calculated the proportions of each sample with comorbid conditions and the
size of sub-populations defined in terms of psychiatric diagnosis and pattern
of substance misuse. We then measured the proportions of comorbid cases that
had been identified by keyworkers. By measuring the severity and types of
comorbid disorder we identified approximate thresholds for access to each
service. We used these data to assess the proportions of each treatment
population with high or low potential for cross-referral and who had
documented contact with both psychiatric and substance misuse services. All
prevalence estimates are reported with exact binomial 95% confidence
intervals. The statistical significance of observed differences in proportions
was assessed using Pearson chi-squared or Fishers exact tests. These
analyses were completed using SPSS (SPSS,
1999).
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We then completed an extended quantitative analysis in relation to comorbid and non-comorbid sample groups in each treatment population. Multiple logistic regression was undertaken using cases with complete data on age, gender, ethnicity and diagnosis to investigate factors independently associated with comorbidity in the London centres v. the aggregated Nottingham and Sheffield centres. Adjusted odds ratios with 95% confidence intervals were obtained and compared with the odds ratios from the univariate analysis. All variables were entered as categorical variables. Interactions between age group, gender, ethnicity, case-mix variables and location were investigated. The coding for ethnicity and age group was predetermined. The statistical package Stata 6.0 (StataCorp, 1999) was used for these latter analyses.
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RESULTS |
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Treatment populations were predominantly male (5767%). Men in contact with drug services and CMHTs had similar median ages (35 years and 36 years respectively) and age group distributions. Patients misusing alcohol were typically older (median age 42 years). In contrast, women in contact with drug services had a younger median age (32 years) than women in contact with alcohol services (39 years) or CMHTs (43 years). There were marked differences in ethnicity between patients comprising the drug and alcohol case-loads (>90% White) and those of CMHTs (68.8% White, 23.8% Black).
Of the CMHT sample, three-quarters (n=216) had a psychotic disorder and 41 had a primary diagnosis of severe depression. Additional complex care needs, which tend to qualify patients for enhanced CPA management, were present in 80% (n=226): these were previous psychiatric admission, suicidal behaviour, self-neglect/harm, risk of exploitation or secondary psychiatric disorder. Most of the drug service patients reported lifetime opiate use (92.6%, n=200), and 78% (n=158) reported lifetime injected drug use. Some alcohol service patients reported controlled drinking in the past year, but 79% (n=49) recorded AUDIT scores indicative of severe alcohol misuse.
Prevalence of comorbidity in CMHT patients
Among CMHT patients, 124 (44%) self-reported drug use and/or harmful
alcohol use (Table 1). Harmful
alcohol use (defined by the AUDIT criteria) was reported by about a quarter of
patients (n=72) and about a tenth (n=26) reported severe
alcohol misuse. Illicit or non-prescribed drug use in the past year was
reported by 87 (30.9%) patients; most met our criteria for problem drug use:
n=64 (29.8%). Drug dependency was identified in 47 (16.7%). The most
frequently reported drugs were cannabis (25.2%, n=71),
sedatives/tranquillisers (7.4%, n=21) and crack cocaine (5.7%,
n=16). Heroin, ecstasy (3,4-methylenedioxymethamphetamine),
amphetamines and cocaine powder were all reported by less than 4%
(Table 1). Harmful alcohol use
was strongly associated with problem drug use. Of the patients who did not
report drug use, 19% had harmful levels of alcohol use. The prevalence of
harmful alcohol use was double this rate in patients reporting any problem
drug use: 40.2% (2=13.7, d.f.=1, P<0.001).
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Table 2 presents the findings of the comparison between self-reported pastmonth drug use and the hair and urine analysis. This shows that virtually no unreported drug use was detected by hair and urine analysis. Although 18 respondents refused to provide samples, 4 of these reported drug use and there was no case in which care coordinators reported drug use that the patient denied.
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Prevalence of comorbidity in drug and alcohol services
Three-quarters of drug service patients (n=161) rated positive for
at least one psychiatric disorder (Table
3). A psychotic disorder was present in 17 patients (8%),
personality disorder in 80 (37%) and severe depression in 58 (27%). The
prevalence of all psychiatric disorders was markedly higher among alcohol
service patients, although the small sample size means that the 95% confidence
intervals for prevalence estimates are wide
(Table 3).
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Comparison of prevalence rates between centres
CMHT populations
Table 4 shows that a
significantly higher proportion of CMHT patients from London centres reported
problem drug use than those from Nottingham and Sheffield (42% v. 21,
2=13.9, d.f.=1, P<0.001). Patients reporting
problem drug use in London centres (n=48) also reported pastyear use
of a higher number of drug types (mean=2.38) than drug-using patients in
Nottingham and Sheffield (n=36; mean= 1.65). Cannabis,
sedatives/tranquillisers and crack cocaine use were all reported by a
significantly higher proportion of patients in London centres than in
Nottingham and Sheffield. The prevalence of any drug dependency was also
significantly higher in patients from the London centres (25% v. 11;
2=8.6, d.f.=1, P=0.005).
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Overall, there was a marked and statistically significant difference in proportions of patients reporting problem drug use and/or harmful alcohol use between London centres and Nottingham/Sheffield. This difference was mainly attributable to the higher reported prevalence of problem drug use in London, as there was no significant difference in the prevalence of harmful alcohol use between London centres and Nottingham/Sheffield.
We completed an extended multivariate analysis to investigate whether the observed differences in prevalence of drug use was explicable in terms of demographic variables (gender, ethnicity, age) and case-mix variables (presence of harmful alcohol use, psychiatric case-mix). This analysis revealed that the univariate odds ratio of problem drug use for patients on a London service case-load was 2.86 compared with Nottingham/Sheffield (95% CI 1.674.90). When the above variables were included in the multiple regression model we found that the adjusted odds ratio (AOR) of problem drug use in London centres over Nottingham/Sheffield was marginally reduced, but a large and statistically significant difference remained (AOR=2.52, 95% CI 1.314.85). Hence, a significant excess in problem drug use exists in the London centres compared with Nottingham and Sheffield which cannot be explained by controlling for the above variables.
We repeated this analysis to assess the association between reported harmful alcohol use in the past year using the same demographic (gender, ethnicity, age) and psychiatric case-mix variables but substituting presence of drug use for presence of harmful alcohol use. The univariate odds ratio of harmful alcohol use for London CMHT patients was 1.18 compared with Nottingham and Sheffield (95% CI 0.682.04). However, as indicated by the confidence interval, the difference in odds is not statistically significant. When the above variables are included in the multiple regression model the adjusted odds ratio of alcohol misuse in London centres over Nottingham and Sheffield is reduced to a marginal level (AOR=1.05, 95% CI 0.522.11). Hence, this series of adjusted analyses showed statistically significant difference in prevalence of drug use between centres after adjustment for the selected case-mix variables. This contributes to a statistically significant difference in comorbidity (problem drug and/or harmful alcohol use). However, there is no evidence of a difference in the prevalence of harmful alcohol use between centres.
Drug and alcohol services
Table 4 compares the
observed prevalence rates of psychiatric disorder in drug service patients
between London centres and Nottingham/Sheffield. Despite a consistent pattern
of marginally higher prevalence in London centres across the spectrum of
disorders, there is no statistically significant difference in the proportions
assessed to have one or more disorder, or a disorder within any of the three
main subgroups assessed (psychosis, personality disorder, affective and
anxiety disorder). We implemented an extended multivariate analysis to assess
whether there was any difference in the odds of comorbidity between the London
and Nottingham/Sheffield samples after adjustment for demographic (gender,
ethnicity, age) and case-mix (presence of alcohol misuse, drug use profile)
variables.
This analysis revealed that the univariate odds ratio of any psychiatric disorder for patients on a London service case-load was 1.47 (95% CI 0.772.80) compared with Nottingham/Sheffield. However, as indicated by the confidence interval, the difference in odds is not statistically significant. When the above variables are included in the multiple regression model the adjusted odds ratio of psychiatric disorder in London centres over Nottingham/Sheffield is marginally reduced (AOR=1.24, 95% CI 0.572.70). Hence, no significant unexplained excess in psychiatric disorder among drug service patients exists in London centres over Nottingham/Sheffield. We repeated the analysis using the presence of psychotic disorder as our outcome variable, with similar results.
Potential for cross-referral of patients
CMHT patients
Just six of the CMHT patients were opiate-dependent and had a high referral
potential for statutory opiate-based drug treatment services. An additional
nine patients reported crack cocaine or other stimulant dependence and would
potentially qualify for brief intervention or referral to stimulant clinics
(if available). Although significant additional numbers were
cannabis-dependent, these patients are unlikely to meet referral criteria
applied by routinely available drug services. (No drug service patient was
dependent solely on cannabis in our sample.) The potential for referral to
alcohol services appears to be greater, given that almost a tenth of patients
(n=26) reported severe alcohol misuse (i.e. AUDIT score >15;
Table 1).
Substance misuse service patients
Non-substance-related psychotic disorder was identified in 17 drug service
patients and 12 alcohol service patients. All exhibited complex care
needs and recorded high CPRS scores (median for drug service patients
22, range 042; median for alcohol service patients 32, range
1354) relative to psychiatric service patients with a psychotic
disorder (median 8, range 038). Hence they were likely to have high
referral potential to CMHTs for enhanced CPA management. A further
1013% in each population had severe depression and complex care
needs, which might have made them candidates for CMHT management. Thus,
in total, 39 drug service patients (18%) and 20 alcohol service patients (32%)
appeared to have a high potential for CMHT referral (see
Table 3).
Identification and management of comorbidity
We compared comorbidity reported by care coordinators and keyworkers with
the relevant reference assessments obtained at interview. Patients without
comorbidity were generally correctly identified as such by services
(specificity >90%). However, substance misuse service patients with
psychiatric disorders and CMHT patients reporting harmful alcohol use were
mostly unrecognised (sensitivity 2038%). Only in relation to CMHT
patients reporting (any) drug use did care coordinators achieve moderately
good sensitivity (60%) (Table
5).
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Small minorities of CMHT patients with comorbidity had received alcohol- or drug-related interventions in the month prior to assessment 15 of 72 reporting harmful alcohol use (21%) and 14 of 84 reporting problem drug use (17%) mostly counselling provided through the CMHT. Seven patients had contact with specialist drug or alcohol services. More patients with high referral potential (as defined above) received substance misuse interventions, but interventions were more likely to be provided to patients with either high or low referral potential if a care coordinator identified the comorbidity problem. For example, 11 of 14 CMHT patients with identified severe alcohol problems received interventions compared with 1 of the 12 whose severe problems were undetected.
More than a fifth of drug and alcohol services patients with comorbidity
(48 of 214) had contact with psychiatric services, of whom 26 (12%) were
allocated to CMHT management during the previous month. Patients with
high referral potential were significantly more likely to have
contact with psychiatric services than those rated low (35/59,
59% v. 13/155, 8%; 2=60.8, d.f.=1,
P<0.001). Some patients with comorbidity reported consultations
with a psychiatrist in the substance misuse service (n=41, 19%) or
with a general practitioner (n=57, 27%) about their mental health
problems, but 32% (n=68) received no intervention. Most of the latter
were patients with undetected, low referral potential problems
(48/68, 71%).
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DISCUSSION |
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Despite these limitations, the study provides strong evidence that comorbidity is highly prevalent in CMHT, drug and alcohol treatment populations. Our findings relating to the profile and management of comorbidity also have major implications for service development.
Prevalence and pattern of comorbidity
Overall, 44% of CMHT patients reported past-year problem drug use and/or
harmful alcohol use. This is higher than previously observed in comparable UK
populations using similar assessment methods (3336%) and is largely
accounted for by a higher level of drug use than previously reported
(Menezes et al, 1996;
Wright et al, 2000;
Duke et al, 2001).
Hair and urine analysis revealed no significant covert drug use and suggested
that these self-reported drug use data provide a reliable and valid basis for
prevalence estimation. Given that consent for obtaining hair and urine samples
was separate from and subsequent to interviews, we can exclude the possibility
that patients were more accurate in reporting drug use because they knew they
were to be tested. The prevalence of harmful alcohol use among CMHT patients
(26%) is consistent with previous estimates (2032%) using self-reported
measures (Menezes et al,
1996; Wright et al,
2000; Duke et al,
2001).
Findings in relation to the validity of prevalence estimates of comorbidity reported by keyworkers at the case-load census have important implications for service development, the interpretation of previously published research and the design of future studies. Studies that have estimated prevalence on the basis of assessments provided by keyworker informants may underestimate prevalence (e.g. Graham et al, 2001; Weaver et al, 2001).
Our findings confirm that comorbidity of severe mental illness and substance misuse is highly prevalent in urban UK mental health settings. However, findings in relation to the level of problem drug use are even more striking when the differences between centres are considered. In the London centres, 42% of CMHT patients reported problem drug use and 25% were assessed as drug dependent. Overall, more than half of London CMHT patients reported substance misuse problems in the past year. We stress the importance of cautious interpretation of these findings, but nevertheless this does appear to confirm the view that patients with such comorbidity may represent the core client group of CMHTs in certain inner-city areas, where the prevalence may be dramatically high (Banerjee et al, 2002).
Large majorities of patients treated for drug and alcohol misuse experience psychiatric disorder, although there was no suggestion that these rates differed significantly between centres in our study. Our estimates for the prevalence of severe depression and personality disorder are consistent with other studies of comparable populations (Regier et al, 1990; Verheul, 2001). However, the prevalence of psychosis (drug service patients 8%, alcohol service patients 19%) was significantly higher than previously reported (Regier et al, 1990) and was 10 times (drug) and 24 times (alcohol) the prevalence rate for psychosis in the urban UK population (0.8%; Jenkins et al, 1998).
Implications for management
In each population studied, comorbid presentations were heterogeneous.
Responding to the level and range of need will be challenging given associated
clinical management problems (Scott et
al, 1998; Hunt et
al, 2002), the current configuration and orientation of
services (Johnson, 1997;
Weaver et al, 1999)
and the difficulty both services have in reliably identifying patients with
comorbid problems. Most drug-using CMHT patients exhibit patterns of use
unlikely to make them eligible for generally available drug treatment
programmes. Even among patients with a high referral potential, a minority had
contact with drug services. Larger proportions of drug and alcohol services
patients with high referral potential had contact with mental health services,
but there was still extensive unmet need for referral and intervention.
Implications for service development and future research
It is evident that parallel or serial treatment
by independent and substance misuse services and CMHTs (as currently
configured) cannot meet the level and range of need presented by comorbid
populations. Integrated treatment teams favoured in the USA to provide
treatment for both types of disorders without cross-referral
(Drake et al, 1995)
lack a strong evidence base (Ley
et al, 1999) and may not be appropriate or replicable in
UK settings (Hall & Farrell,
1997; Johnson,
1997; Weaver et al,
1999). Moreover, there is a danger that the development of
integrated teams could result in drug and alcohol services remaining
underresourced and narrowly focused (i.e. upon opiate use, in the case of drug
services). Instead, we support current efforts to develop the capacity and
competency of mainstream services
(Banerjee et al,
2002).
Drug and alcohol treatment services already provide mental health interventions (both pharmacological and psychotherapeutic) to significant numbers of their patients with mental health problems. However, there were equally large numbers of patients with comorbidity whose needs were unmet or unidentified. Resources need to be deployed enabling substance misuse services to offer evidence-based treatments to a much higher proportion of these patients (Hall & Farrell, 1997). Models of collaborative working with local general practitioners and psychotherapy services (in addition to general adult psychiatry) should be developed and evaluated. In relation to CMHTs, our findings suggest that mainstream staff need to be able to implement at least basic management of comorbidity. To achieve this, staff are likely to need enhanced training in the assessment of drug and alcohol problems (and in the use of appropriate evaluation tools), as well as motivational techniques to improve patient engagement with substance misuse treatment and achieve harm minimisation goals. Interventions to address these skill deficits require urgent evaluation.
Although enhanced training has rightly been identified as a key component of our response to comorbidity (Banerjee et al, 2002), there is also a need to resource, develop and evaluate new service-based assessment, treatment and management approaches, which can support psychiatric and substance misuse services in offering evidence-based treatments to much higher proportions of their patients with problems of comorbidity.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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The COSMIC study group consists of the following members: Imperial College, London: Tim Weaver, Vikki Charles, Zenobia Carnwath, Peter Madden, Adrian Renton, Gerry Stimson, Peter Tyrer, Thomas Barnes, Chris Bench and Susan Paterson; Turning Point, Brent: Chris Ford; Central and North West London Mental Health NHS Trust: Jonathon Greenside, Owen Bowden Jones and William Shanahan; Community Health Sheffield NHS Trust: Helen Bourne, Muhammad Z. Iqbal and Nicholas Seivewright; Nottingham Healthcare NHS Trust: Sylvia Cooper, Katina Anagostakis, Hugh Middleton and Neil Wright.
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Received for publication November 27, 2002. Revision received May 12, 2003. Accepted for publication May 13, 2003.
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