The impact of substance use disorders on the course of schizophrenia--a 15-year follow-up study: dual diagnosis over 15 years.

BACKGROUND

This follow-up study compared patients with schizophrenia with co-occurring substance use disorder to patients with schizophrenia and no substance use disorder.

AIMS

To investigate the prognostic significance of the effects of substance use disorders on the course of schizophrenia.

METHOD

Patients with schizophrenia and co-occurring substance use disorder (n=107), and patients with schizophrenia only (n=119) were followed over a 15-year period through the use of national hospitalization registers, data for time and cause of death, and data for homelessness or institutionalization.

RESULTS

The median length of psychiatric hospitalization was 12 days for a patient with dual diagnosis, and 21 days for patients with schizophrenia only. Patients with dual diagnosis displayed a significantly elevated usage of all types of hospital contacts except inpatient treatment for non-psychiatric disorders. In three types of hospital contacts, patients with co-occurring substance use had approximately two to three times as many hospitalizations as did patients with schizophrenia only. Rates for homelessness and institutionalization were similar in both groups. Patients with a dual diagnosis were also significantly more at risk of dying during follow-up than were patients with schizophrenia only.

CONCLUSIONS

The findings suggest that the long-term course of schizophrenia is considerably more severe in patients who have a dual diagnosis compared to patients with schizophrenia only Substance use disorders have a substantial impact on the hospitalization rates of patients with schizophrenia, as well as on life expectancy. Patients with co-morbid substance abuse are more likely to be admitted for treatment during a given year although they have briefer contact with treatment.