Use of drugs, alcohol and tobacco by people with schizophrenia: case-control study
McCreadie RG; Scottish Comorbidity Study Group;
Commented by , 16 Dec 2002
Aim of the study
Comorbid substance abuse has been identified as a major research focus in the field of schizophrenia. The Scottish office of the Royal College of Psychiatrists has even suggested the development of specialised services to help people with schizophrenia and associated substance misuse.
However, the exact extent of the problem is largely unknown. Previous studies on the topic did not use an accurate case definition, most have taken place in cities and only few have made direct comparisons with the local population.
To fill this gap, the authors determined the use of drugs, alcohol and tobacco by people with schizophrenia drawn from rural, suburban and urban settings, and compared the results with control subjects drawn from the general population.
Method
The study took place in three Scottish sites: the first one was mainly rural, the second one urban and the third one suburban to cover a representative population.
People with schizophrenia (n=316) were identified and diagnosed using ICD-10 criteria. General population controls (n=250) were identified in the same areas and matched according to gender distribution, age and postcode area of residence. Use of drugs and alcohol was assessed by the Schedules for Clinical Assessment in Neuropsychiatry, and use of tobacco by a questionnaire.
Results
The clearest difference between patients and controls was smoking. 65% of the patients versus only 40% of the controls were current smokers (p<0.001).
Statistically significantly more patients than controls reported problematic use of drugs in the past year (7% versus 2%) and at some time before then (20% versus 6%).
Problematic use of alcohol was also statistically significantly more frequent among patients in the past year (17% versus 10%), but not at some time previously (40% versus 34%).
Discussion
The authors conclude that tobacco use is the greatest problem in terms of concomitant substance abuse. Almost two thirds of the patients were smokers. They also state that problematic use of drugs and alcohol by people with schizophrenia is greater than in the general population, but that absolute numbers are small, especially for drugs.
Indeed, the fact that 93% and 83% of the patients did not have problematic use of drugs or alcohol in the previous year is somewhat surprising, because a widely quoted American study reported lifetime prevalence for substance abuse of 47%. Different study designs and different populations studied (Scottish versus American) may be reasons for these differences.
Furthermore, a methodological problem of the current study was that in a small sample of controls who did not report drug use, hair analysis suggested otherwise. Finally, the reasons of substance abuse were not investigated in this study. Previous reviews of the literature have suggested that drugs might be used to self-medicate symptoms of illness or drug side-effects.