Caffeine intake in outpatients with schizophrenia.

Several studies suggest that caffeine intake is high in patients with schizophrenia and a few of them suggest that caffeine may contribute to schizophrenia symptomatology. None of these studies control for the effect of tobacco smoking, which is associated with induction of caffeine metabolism. Therefore, the high amount of caffeine intake among patients with schizophrenia may be due to their high prevalence of smoking. This is the first large study to explore whether caffeine intake in patients with schizophrenia is related to tobacco (or alcohol) use or to the severity of schizophrenia symptomatology. The sample included 250 consecutive consenting outpatients with a diagnosis of DSM-IV schizophrenia from Granada, Spain. Fifty-nine percent (147/250) of patients consumed caffeine. Current caffeine intake was associated with current smoking and alcohol use. As none of the females used alcohol, the association with alcohol was only present in males with schizophrenia. Among caffeine consumers, smoking was associated with the amount of caffeine intake. Cross-sectional schizophrenia symptomatology was not associated with caffeine intake.