[Do alcohol or drug abuse induce schizophrenia?]

The high comorbidity of schizophrenia and substance abuse raises the question of a causal relationship between the two disorders. Clarifying the temporal sequence of their onsets can shed light on this issue. For this purpose, onset and course of schizophrenic symptoms and of alcohol and drug abuse were retrospectively investigated within the ABC Schizophrenia Study in a representative first-episode sample of 232 schizophrenic patients. The rates of alcohol abuse (24%) and of drug abuse (14%) were twice the rates compared to the general population but schizophrenic patients seemed to have started substance abuse later than the control group. Male sex and early symptom onset were major risk factors. At all important landmarks during the early course of schizophrenia, drug-abusers were younger than alcohol-abusers who were younger than non-abusers. Alcohol abuse usually started during the prodromal phase, i.e., after the first sign of schizophrenia but before the first positive symptom. Drug abuse emerged before the first symptom in one third, simultaneously with it in another third, and during the prodromal phase in the last third of patients. Drug abuse significantly preceded the psychotic phase. The hypothesis that substance abuse causes schizophrenia thus is not generally supported. Findings on symptomatology illustrate the problems substance-abusing schizophrenics pose from early on with dissocial behaviors and preoccupation with magical ideas but without a specific positive or negative subsyndrome.