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A group of patients (N = 1630) hospitalized in Stockholm County with a diagnosis of substance abuse during 1971-1972 were followed through 1984 as regards mortality: 446 (296 males and 150 females) patients died. The excess mortality in the cohort was 5.3 (males 5.8, females 4.6) compared to the general population in Stockholm County. The highest mortality was found in opiate users, with an excess mortality of 18.3. Fifty-one percent of the causes of death belonged to ICD-8 chapter 17, injury and poisoning, and of these, 69% (155 patients) were definite or probable suicides. Since HIV entered the Stockholm drug addict population by the end of this follow-up, the excess mortality reported here can be even higher in the years to come. To follow and monitor the mortality among patients with substance abuse is an important aspect in the evaluation of programs for prevention and treatment.

By means of the Stockholm County inpatient care register we identified all cases treated with a diagnosis of cannabis dependence and psychosis, not necessarily at the same occasion, during 1971-1983. By scrutinizing medical records, we evaluated the diagnosis according to DSM-III-R and we assessed the history of substance abuse as well as the psychiatric history and clinical course. We identified 229 cases during the follow-up; 112 of these cases (49%) fulfilled the DSM-III-R criteria for schizophrenia. The majority of the schizophrenics had prominent positive symptoms and a sudden onset of disease, and 69% of the cases had a record of heavy cannabis abuse at least 1 year before onset of psychotic symptoms. The high number of verified DSM-III-R cases of schizophrenia in this cohort and the temporal relation between cannabis abuse and schizophrenia further support the hypothesis that cannabis abuse may be a risk factor for schizophrenia. We confirmed previous observations that cannabis-associated schizophrenia often has a sudden onset and prominent positive symptoms.

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