Substance abuse and cognitive functioning in schizophrenia.

Individuals with schizophrenia have an increased vulnerability to abuse drugs or alcohol. This vulnerability can interfere with the course and treatment of the disorder and may also have a detrimental effect on already compromised cognitive functioning. This study has a matched, cross-sectional design and compares the social and cognitive functioning and the symptoms of 33 schizophrenia subjects who abuse substances with 33 nonabusing schizophrenia subjects. Subjects were matched on sex, age, and education variables and were all outpatients. Measures of social functioning and quality of life were used. Assessment of cognitive functioning included measures of verbal ability, attention, executive functioning, and verbal and visual memory. Substance-abusing subjects had significantly lower quality of life. There were no other differences between the 2 groups. Several explanations are offered for the lack of observed differences in cognitive functioning.