NATURAL HISTORY OF SUBSTANCE USE DISORDERS

As a backdrop to understanding the longitudinal course of psychiatric and substance use disorders, it is helpful to review what is known about the course of primary alcohol and drug use disorders. Vaillant's (1983) seminal work on the natural history of alcoholism provides compelling evidence that for most clients the disorder is lifelong and is associated with a substantial risk for early mortality. Despite the overall negative (and often progressively negative) longterm outlook for alcoholics, a cumulative proportion of individuals

achieve abstinence, even in the absence of professional treatment. Vaillant (1983) estimated that approximately 3 percent of alcoholics become abstinent each year without the benefit of formal treatment programs, and between 1 and 2 percent of abstinent alcoholics resume social drinking. Although the efficacy of treatment for alcoholism continues to be debated, Vaillant (1983) estimated that treatment of alcoholics increases their recovery rate to approximately 6 percent yearly. Fewer data are available on the longitudinal course of primary drug use disorders, although in general the findings are compatible with those reported by Vaillant (1983) for alcoholism (Vaillant 1973, 1988; Simpson et al. 1986). In one of the largest and longest longitudinal studies published to date, Hser and associates (1993) reported 24-year outcomes for 581 narcotics addicts who had been admitted to the California Civil Addict Program between 1962 and 1964. Data on the long-term outcome of these patients' drug use disorders revealed high mortality rates and a rate of spontaneous remission in the absence of treatment that was somewhat lower than that reported by Vaillant (1983) for alcoholics. At the end of the followup period, 28 percent of the sample were dead, and only 19 percent had attained stable abstinence, which was defined as not using drugs for the prior 3 years. Interpretation of the negative long-term outcome for the Hser and colleagues’ (1993) study should to be tempered by recognition that the sample probably represented a more severely ill group of drug abusers than the alcoholics studied by Vaillant (1983). For example, the narcotics addicts studied by Hser and associates (1993) met criteria for a drug use disorder at an early age and were involved the legal system. Despite differences across longitudinal studies in sample characteristics, research on the natural course of primary alcohol and drug use disorders indicates that these disorders are usually chronic over a lifetime. There is considerable variation in clients' substance use behavior over time, but relatively few spontaneously attain stable abstinence, and clients are at increased risk of early mortality. Although the available evidence indicates that substance use disorders are relatively chronic over the lifetime, illicit drug use is not. Recent epidemiological surveys indicate that most people in the United States cease using illicit drugs by the age of 30 and that heavy drinking declines at around the same age range (Chen and Kandel 1995). It appears that substance use disorders tend to be chronic over long periods of time, but that alcohol and drug use behavior in the nonabusing population tends to decline with age over time. Very little research has examined the natural history of substance use disorders in people with severe mental illnesses. However, the available data suggest that the outcome of dually diagnosed persons who receive services from the traditional parallel treatment system is bleak. Several prospective studies have shown increased rates of hospitalization over 1 year for psychiatric clients with a substance use disorder (Drake et al. 1989; Osher et al. 1994). Furthermore, in one study even minimal levels of drinking, not considered abuse by clinicians, predicted rehospitalizations (Drake et al. 1989). One-year followup studies also show little remission of substance use disorder (Drake et al. 1996). In line with the evidence indicating that substance abuse frequently precipitates disruptive behavior, symptom exacerbations, and rehospitalizations, researchers in the McKinney demonstration project on homeless mentally ill adults concluded that sub-stance use disorders were the single most important factor contributing to housing instability in this population (Center for Mental Health Services 1994). In perhaps the longest longitudinal study of dually diagnosed persons, Bartels and colleagues (1995) conducted followup assessments 7 years after an initial evaluation on 148 out of 170 (86 percent) severely mentally ill clients. At baseline, 24 percent of the sample had an alcohol use disorder, and at followup 21 percent had such a disorder, a nonsignificant difference. Similarly, the rate of drug use disorder also did not change significantly from baseline (20 percent) to followup (17 percent). Despite these essentially negative findings, some clients were successful in becoming abstinent from substance use. Over the 7 years, 25 percent of the clients with an alcohol use disorder and 35 percent clients with a drug use disorder at initial evaluation achieved abstinence. Furthermore, clients with substance abuse diagnoses were more likely to attain abstinence than those with substance dependence diagnoses. The lack of change in the overall rate of substance use disorders across the two assessments of the Bartels and colleagues (1995) study reflects the fact that some clients who did not meet criteria for a substance disorder at the baseline assessment met the criteria at followup. Indeed, in two separate samples, Drake and Wallach (1993) found that clients with severe mental illness but who appeared to be moderate, nonabusive drinkers were likely to develop alcoholism over several years. This finding is also consistent with Cuffel and Chase's (1994) analysis of the stability of substance use disorders over 1 year in persons with schizophrenia. Thus, dual-diagnosis clients tended to recover from substance use disorders at very slow rates, although there is considerable fluctuation in and out of the disorder among those who are moderate users and those with abuse rather than dependence. In summary, most clients with a primary alcohol or drug use disorder have a chronic course of illness, with the actual substance use behavior varying greatly over time and a small percentage of people attaining stable abstinence each year (i.e., less than 5 percent per year). In addition to the financial and psychosocial consequences associated with substance use disorders, these clients are also at increased risk for early mortality. The small amount of information currently available about the natural history of dually disordered clients suggests a similar picture, complicated by an increased risk for disruptive behavior, hospitalizations, and psycho-social problems.