Department of Clinical Research, Crichton Royal Hospital, Dumfries DG1 4TG, UK.
Correspondence: Tel: +44 (0) 1387 244000; fax: 44 (0) 1387 257735; e-mail: rgmccreadie_crh{at}compuserve.com
Declaration of interest None. The study was funded by the Chief Scientist Office, Scottish Executive, Edinburgh.
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ABSTRACT |
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Aims To determine the use of drugs, alcohol and tobacco by people with schizophrenia drawn from rural, suburban and urban settings, and to compare use by general population control subjects.
Method People with schizophrenia (n=316) and general population controls of similar gender distribution, age and postcode area of residence (n=250) were identified in rural, urban and suburban areas of Scotland. Use of drugs and alcohol was assessed by the Schedules for Clinical Assessment in Neuropsychiatry, and use of tobacco by a questionnaire.
Results More patients than controls reported problem use of drugs in the past year (22 (7%) v. 5 (2%)) and at some time before then (50 (20%) v. 15 (6%)) and problem use of alcohol in the past year (42 (17%) v. 25 (10%)) but not at some time previously (99 (40%) v. 84 (34%)). More patients were current smokers (162 (65%) v. 99 (40%)).
Conclusions Problem use of drugs and alcohol by people with schizophrenia is greater than in the general population, but absolute numbers are small. Tobacco use is the greatest problem.
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INTRODUCTION |
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METHOD |
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Subjects
Case finding in Nithsdale uses the key informant method
(McCreadie, 1982). Regular
censuses identify all current inpatients, day patients and out-patients at
Crichton Royal Hospital, Dumfries and patients supported by community
psychiatric nurses. These patients have a consensus clinical ICD-10 diagnosis
of schizophrenia (World Health
Organization, 1992) and a home address in Nithsdale. In addition,
general practitioners (GPs), mental health officers (social workers) and
voluntary agencies identify any others known to them. The key informant method
was also used to identify patients in west Glasgow and Aberdeen.
As stated above, all patients had a consensus clinical diagnosis of schizophrenia. In addition, patients' records were examined and the Operational Checklist for Psychiatric Disorders (OPCRIT; McGuffin et al, 1991) completed. The OPCRIT-associated computer program was used to generate research ICD-10 and DSM-IV (American Psychiatric Association, 1994) diagnoses.
General population controls
In Nithsdale and Glasgow, through the use of the Community Health Index (a
national database that holds details for all patients registered with a
Scottish GP), and in Aberdeen, through scrutiny of patients' lists in the five
general practices, a general population control was identified for each
patient, matched for gender, age (within 1 year), and postcode area of
residence (matched to five characters). Controls were not sought for patients
continuously an in-patient for more than 6 months.
Assessment of rates of drug, alcohol and tobacco use
Research nurses interviewed all patients and controls. Prevalence rates of
use of drugs and alcohol in the previous year, and at any time before then,
were measured using sections 11 and 12 of the Schedules for Clinical
Assessment in Neuropsychiatry (SCAN; World
Health Organization, 1994). Subjects were then classified as
having no use, harmful use, dependence or problem use (harmful use and/or
dependence) on the basis of ICD-10 criteria in the year before the interview,
or at any time before then. Current substance use was also assessed in
patients through keyworker ratings, using a five-point scale: abstinence; use
without impairment; misuse; dependence; and severe dependence
(Drake et al, 1989;
Menezes et al, 1996).
Patients and control subjects completed a questionnaire on smoking recently
used in a health and lifestyle survey of the general population in south-west
Scotland (Waldron et al,
1995).
As a check on patients' and control subjects' reports, every 20th patient and control was asked to give a hair and urine sample, the former to assess use in the past 3 months of amphetamines, metamphetamines, benzodiazepines, methadone, opiates and cocaine, and the latter to assess cannabis use.
Statistical analysis
For univariate comparisons between cases and controls, chi-squared tests
for differences in proportions were used, together with calculation of odds
ratios and confidence intervals. Multivariate analysis to determine the
independence of factors was based on conditional logistic regression.
Differences significant at least at the 5% level are reported.
Ethical approval
The study was approved by the relevant local research ethics committees.
All patients and controls gave written informed consent.
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RESULTS |
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More matched than unmatched patients were in the most deprived social
categories (6 or 7), (23 (37%) v. 42 (17%), 2=12.1,
d.f.=1, P=0.001, OR=0.4, 95% CI 0.2-0.7). Consequently, only matched
patientcontrol pairs were included in the comparisons between patients
and controls. More patients were single (162 (65%) v. 60 (24%),
2=84.3, d.f.=1, P<0.001, OR=5.8, 95% CI 3.9-8.6),
lived alone (116 (46%) v. 55 (22%),
2=33.1, d.f.=1,
P<0.001, OR=3.1, 95% CI 2.1-4.5) and were unemployed (225 (90%)
v. 76 (30%),
2=187.4, d.f.=1, P<0.001,
OR=21.5, 95% CI 13-35.4).
Use of drugs
Taking all patients into account, 22 (7%) reported problem use of drugs in
the past year (5 problem use with opiates and 13 with cannabis), and 66 (21%)
at some time before then. Those who had problem use over the past year were
more often male (19 (10%) v. 3 (3%), 2=5.8, d.f.=1,
P=0.02, OR=4.1, 95% CI 1.2-14.3), younger (mean age 34 years (s.d. 6
years) v. 46 years (s.d. 14); t-test: t=3.9,
d.f.=314, P<0.001; 95% CI for difference between means 6.1-18.7)
and lived in more deprived areas (most deprived: 12 (55%) v. 53
(18%):
2=16.5, d.f.=2, P<0.0001, OR=5.4, 95% CI
2.2-13.1).
Significantly more patients than controls reported harmful use, dependence or problem use of drugs, both in the past year and at some time before (Table 2).
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Of 316 patients rated by key informants, 26 (9%) had current misuse, dependence, or severe dependence on drugs. Through the SCAN, 14 of these 26 were rated as having problem use of drugs over the past year. Of 56 urine samples tested for cannabis, one was positive, a patient who had reported recent use. Of 40 hair samples tested, 7 (18%) yielded positive results for any drug (5 for opiates, 1 patient and 4 controls). The patient and one control had reported recent use. One patient and one control tested positive for sedatives, and although neither reported use, the patient had received a prescribed sedative. One control tested positive for stimulants and had not reported use.
Use of alcohol
Taking all patients into account, 49 (16%) reported problem use of alcohol
in the past year and 122 (39%) at sometime before then. Those who had problem
use of alcohol over the past year were more often male (39 (20%) v.
10 (8%), 2=7.4, d.f.=1, P=0.006, OR=2.7, 95% CI
1.3-5.6), and younger (mean age 39 years (s.d. 10) v. 46 years (s.d.
14); t-test: t=3.4, d.f.=314, P=0.001, 95% CI for
difference between means 3.1-11.5). Significantly more patients than controls
reported harmful use, dependence or problem use of alcohol in the past year
and dependency at some time previously
(Table 3).
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When rated by key informants, 41 (15%) of 316 patients had current misuse, dependence or severe dependence on alcohol. Through the SCAN, 22 of these 41 were rated as having problem use of alcohol over the past year.
Alcohol and/or drug use
More patients than controls had problems with alcohol or drugs in the past
year (64 (20%) v. 30 (12%); 2=6.9, d.f.=1,
P=0.008, OR=1.9, 95% CI 1.2-2.9), but not at some time previously.
Seven patients and one control had problems with both drug and alcohol use in
the past year.
Use of tobacco
Taking all patients into account, 205 (65%) were current smokers. More male
than female patients were current smokers (141 (72%) v. 64 (54%),
2=10.1, d.f.=1, P=0.002, OR=2.2, 95% CI 1.3-3.5) and
current smokers were younger (mean age 43 years (s.d. 13) v. 49 years
(s.d. 16); t-test: t=3.3, d.f.=314, P=0.001, 95% CI
for difference between means 2.4-9.1).
Significantly more patients than controls were current smokers (162 (65%)
v. 99 (40%), 2=33.0, d.f.=1, P<0.001,
OR=2.9, 95% CI 1.9-4.1), and of those who smoked cigarettes as opposed to
roll-ups, more patients were heavy smokers (20 or more
cigarettes/day; Table 4) (95
(76%) v. 38 (46%),
2=18.9, d.f.=1,
P<0.001, OR=3.7, 95% CI 2.0-6.7).
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Multivariate analysis
Conditional logistic regression, comparing patients with controls, was
carried out using the following factors: site (Nithsdale, Glasgow, Aberdeen),
current smoking, problem with drugs and problem with alcohol. The analysis was
carried out for problems both in the past year and at any time before that.
Numbers of current smokers were significantly different in both analyses
(P<0.001 in both cases), as were numbers with problems with drugs
(P=0.04, P<0.001). Although there were no differences in
numbers having problems with alcohol, further analyses examining harmful use
and dependence found that more patients had harmful use in the past year
(P=0.04) and dependence at some time previously
(P=0.03).
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DISCUSSION |
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Methodological issues
Identification of patients
With regard to identification of patients, it was probably more
comprehensive in Nithsdale than in Glasgow and Aberdeen as there has been over
20 years' experience in that area in identifying patients by the key informant
method. This is reflected in similar prevalence rates in the three areas; the
prevalence of schizophrenia is probably less in a rural area
(Torrey & Bowler,
1990).
Identification of controls
The identification of control subjects was slightly different in the three
areas. Although in all three centres controls were obtained through GPs'
patient lists, in Nithsdale and Glasgow it was through a national database,
but in Aberdeen it was through a search of patient records in GPs'
surgeries.
Not all patients identified were interviewed. It is possible that more of the patients identified but not interviewed had drug or alcohol problems. Yet, the distribution of the demographic factors associated with problem use (age and gender) was the same in those interviewed and not interviewed. It is also possible that patients and controls underreported their use. Hair and urine analysis, albeit in a small number of people, did not identify recent use of any non-prescribed drug in any patient who denied it; in contrast, four controls tested positive and had not reported use.
On SCAN interview patients reported alcohol and drug problems which key workers failed to identify, and vice versa. Although we cannot be certain, we believe that a detailed interview lasting 1-2 hours by a research nurse will give more accurate information than a brief interview with a keyworker. In previous reports, one found that keyworkers overestimated and the other found they underestimated drug misuse (Menezes et al, 1996; Brown, 1998).
Comparison with other studies
Problem use of drugs over the previous year (7%) was a little lower than in
a 6-month prevalence study of community patients in a rehabilitation service
in Southampton, UK (Brown,
1998), where 10% reported misuse of illicit drugs and 15% misuse
of prescribed drugs over the previous 6 months, and in patients with psychosis
in a community in south London (Menezes
et al, 1996), where 11% reported misuse in the previous
year. In both these urban-based studies, however, patients were considerably
younger. In both these studies and ours, a younger age was associated with
more drug misuse.
The number of patients reporting problem use of alcohol in the past year (16%) is similar to that in Southampton (18%; Brown, 1998) but lower than in south London (32%; Menezes et al, 1996). However, the latter study contained patients with depressive psychosis, of whom two-thirds had a problem with alcohol. Problem use at some time previous to the year before assessment in our study (39%) was higher than lifetime problem use in a community sample of patients with schizophrenia in inner London (Duke et al, 1994).
Although absolute numbers were small, more people with schizophrenia than control subjects had problems with drugs both in the past year or at some time previously and, with regard to alcohol, harmful use in the past year or dependence at some time previously. What leads more people with schizophrenia to substance misuse has been discussed extensively (Siegfried, 1998; Blanchard et al, 2000). They may misuse drugs for the same reasons as the rest of the population (to relax, increased availability, increased acceptability). Drugs might be used to self-medicate symptoms of illness or drug side-effects. Finally, genetic factors could lead to both drug misuse and schizophrenia. We would like to emphasise, however, that in our study 93% and 84% of patients respectively did not have problem use of drugs or alcohol in the previous year.
Tobacco
Use of alcohol or drugs in our patients was greatly overshadowed by use of
tobacco. Almost two-thirds of our patients were current smokers, and most who
smoked were heavy smokers. These findings are similar to a recent survey of
smoking in south-west Scotland (Kelly
& McCreadie, 1999), but it is a somewhat lower rate than that
found in a widely quoted American study
(Hughes et al, 1986), where 88% of out-patients with schizophrenia were smokers. A future paper
(further details available from the author upon request) will examine service
use by those who do and do not have current problem use of drugs or alcohol,
and discuss the need, or otherwise, for dual diagnosis clinics. However, in
our view the most important dual diagnosis is schizophrenia and tobacco use.
Patients with schizophrenia die early, especially from smoking-related
diseases (Brown et al,
2000). Attempts to help people with schizophrenia give up smoking
should be a top priority.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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REFERENCES |
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Received for publication November 30, 2001. Revision received May 7, 2002. Accepted for publication May 29, 2002.