Comorbidity of Axis I and II mental disorders with schizophrenia and psychotic disorders: findings from the National Epidemiologic Survey on Alcohol and Related Conditions.

Objective: To examine the comorbidity of Axis I and II disorders within a community-based sample of adults with schizophrenia.
Methods: The study was conducted using data from the National Epidemiologic Survey of Alcohol and Related Conditions. A diagnosis of schizophrenia was based on respondents' self-report that they had been diagnosed by a health professional with schizophrenia or a psychotic illness or episode (SPIE). Axis I disorders and Axis II personality disorders (PDs) were assessed using the Alcohol Use Disorders and Associated Disabilities Interview Schedule. Mental and physical quality of life were assessed using the Medical Outcomes Study Short Form 12 questionnaire.
Results: The prevalence of SPIE was 0.9%. We used multiple logistic regression to examine the association between the presence and absence of SPIE in Axis I and II mental disorders. Each of the Axis I and II mental disorders examined were significantly associated with a diagnosis of SPIE after controlling for age, sex, education, marital status, and household income.
Conclusions: Clinicians should be aware of the patterns and extent of psychiatric comorbidities that may exist in schizophrenia. Possible mechanisms of these associations are discussed.