Precipitation and determination of the onset and course of schizophrenia by substance abuse — a retrospective and prospective study of 232 population-based first illness episodes

Abstract

Onset and lifetime prevalence of substance abuse were assessed retrospectively using the IRAOS interview in a population-based, controlled sample of 232 first episodes of schizophrenia (ABC sample). Subjects with schizophrenia were twice as likely as controls to have a lifetime history of substance abuse at the age of first admission (alcohol abuse: 23.7 versus 12.3%; drug abuse: 14.2 versus 7.0%). 88% of the patients with drug abuse took cannabis. The sequence of substance abuse and schizophrenia was studied on the timing of abuse onset and illness onset, the latter as based on various definitions: first sign of the disorder, first psychotic symptom and first admission. 62% of the patients with drug abuse and 51% of those with alcohol abuse began the habit before illness onset (=first sign of the disorder). Abuse onset and illness onset occurred highly significantly within the same month (drug abuse in 34.6%, alcohol abuse in 18.2%). Unexpectedly, no temporal correlation was found between abuse onset and the onset of the first psychotic episode. We concluded that a small proportion of schizophrenias might have been precipitated by substance — mainly cannabis — abuse.

Long-term effects of early substance abuse were studied prospectively at six cross-sections over five years from first admission on in a subsample of 115 first episodes of schizophrenia. Abusers showed signficantly more positive symptoms and a decrease in affective flattening compared with controls. Five-year outcome as based on treatment compliance, utilization of rehabilitative measures and rate of employment was also poorer for patients with than without early substance abuse.

Introduction

The abuse of illegal drugs, such as cannabis, amphetamines, cocaine and hallucinogens, more rarely opioids, is more frequent in persons with schizophrenia than in other mental patients or in the general population (Smith and Hucker, 1994, Mueser et al., 1992a, Kovasznay et al., 1997). According to a metaanalysis of US studies every third person diagnosed with schizophrenia has an alcohol problem (Cuffel, 1992).

The frequency of abuse as well as the type and amount of the substances abused depend on the duration of exposition, e.g. length of illness and availability of the substances of abuse in the population studied. The overall lifetime prevalence of alcohol abuse ranges from 12.3 (Alterman et al., 1981) to 42.8% (Barbee et al., 1989), that of cannabis abuse from 35 to 60% (Negrete et al., 1986). DeLisi et al. (1991) found a lifetime prevalence of 35% for drug abuse among 100 first-episode cases of schizophrenia in the State of New York. Soyka et al. (1993) found a lifetime prevalence of 21.8% for drug abuse among patients with recent-onset schizophrenia and of 42.9% among chronic patients in Bavaria/Germany. The corresponding figures for alcohol abuse were 17.4 and 34.6%, respectively. In chronic schizophrenia multiple abuse of different drugs and alcohol is wide spread (Drake et al., 1989, Rosenthal et al., 1994).

Finally, as Mueser et al., 1992a, Mueser et al., 1992b pointed out, contributing to the high variation in the rates reported are also methodological flaws frequent in the studies, such as non-uniform instruments of assessment, small sizes and lack of representativity of the samples studied.

Valid results on substance abuse in schizophrenia can only be obtained by studying sufficiently large representative samples of persons with a diagnosis of schizophrenia, by collecting precise data on the duration of both the illness and substance abuse and by comparing these cases with matched controls drawn from the same population of origin. To find out whether schizophrenia is triggered by substance abuse schizophrenia precise data on the time of onset of both the disorder and substance abuse are needed (Lieberman and Bowers, 1990, Linszen et al., 1994).