mental illness and substance abuse are considered to be different disorders using current diagnostic guidelines, the boundaries between them may not be so distinct. In fact, workshop participants suggested that mental illness and substance abuse may be two different aspects of a common pathology.
By evaluating how such disorders occur in families and communities, insights as to patterns and sources of comorbidity can be ascertained. Dr. Merikangas reported on epidemiological studies demonstrating strong associations between psychiatric disease and substance abuse. The magnitude of the association increased with greater severity of disease. A retrospective international study examined comorbidity in eight countries (from North and South America and Europe). Despite fairly large differences in base rates among the countries, the patterns of comorbidity were virtually identical. Temporal patterns of comorbidity revealed that anxiety disorders and conduct problems tended to precede alcohol and drug problems, whereas affective disorders both preceded and post-dated the onset of substance abuse disorders. Depression was reported equally often before and after the onset of alcohol or drug abuse. Bipolar disorder seemed to precede substance abuse, whereas panic disorders tended to begin subsequent to the onset of substance abuse. However, because the order of onset of the conditions in this study was determined retrospectively, the findings may be subject to recall bias. This limitation could introduce inaccuracies into these data.
To provide a more accurate assessment of temporal and developmental relationships in comorbidity, an ongoing prospective study is tracking children of parents with substance abuse and other psychiatric disorders. Analyses of 8 years of data have begun to demonstrate premorbid risk factors and early signs of emotional and behavioral disorders that may predispose individuals to develop substance use disorders. This study, for example, has shown that persons with anxiety disorders tend to use alcohol and drugs to ameliorate their anxiety, thereby suggesting an important target for early interventions with the primary disorder to prevent the secondary condition.
Drs. Steadman and Monahan presented results of a study on about 1,000 people who had recently been discharged from mental hospitals. The incidence of violence and the impact of substance abuse on violence in this population were examined. Reports from the patients and from a collateral person (i.e., an individual familiar with the patient 's activities), as well as official records were collected every 10 weeks for 1 year after discharge. The average hospital stay was 9 days. The incidence of violent acts peaked near the time of hospitalization and decreased throughout the following year.
For each major mental disorder evaluated in the study (i.e., depression, schizophrenia, bipolar disorder), 40%–50% of the patients also had a history of substance abuse. Of those patients with co-occurring major mental illness and substance abuse, 31% committed at least one violent act during the course of the year. When a patient's social context was considered, co-occurring mental illness and substance abuse continued to be associated with a greater incidence of violence. Among individuals who abused drugs or alcohol the incidence of violence was significantly higher in patients with mental illness than in people from the same community without mental illness. Yet, patients without co-occurring substance abuse were only slightly more likely to commit violent acts than were other members of the same community. Dr. Robert Drake pointed out that a dual diagnosis of drug abuse and mental illness was correlated with relapse, violence, incar