Patterns of substance use in schizophrenia: a Markov modeling approach

Markov models were used to examine patterns of substance use and global functioning in a sample of 100 schizophrenic outpatients over an 18 month period. Patterns of changes in substance use and functional status were stable across the evaluation period. Persons remaining in any substance use or functional state for two evaluation periods were highly likely to continue in the same state. Tests of two common causal hypotheses about relationships between substance use and functional status yielded partial support for the hypothesis that substance use leads to functional impairment, but did not support the hypothesis that functional impairment leads to substance use. Furthermore, there was no evidence of any increase in overall substance use or of substance use leading to treatment dropout. These analyses illustrate a promising approach to key questions about substance use in schizophrenia.