multiple sclerosis, postinfectious encephalomyelitis, paraneoplastic diseases, Alzheimer's disease, and even schizophrenia. Shared mechanisms may be involved whenever an abnormal gene provokes immune responses with potential to include neurotoxic responses.
The primary motivation to study ADC and HIV infection of the CNS is to treat the disability they cause. While the prevalence of ADC is still somewhat uncertain, it remains a significant complication of HIV infection, and its severe impact on the lives of patients makes it an important target of prevention and treatment. As opportunistic infections are increasingly prevented by antibiotic prophylaxis, an increase in the prevalence of ADC threatens, although such a trend has not appeared in national statistics. In evaluating antiretroviral and other therapies, the study of ADC may also prove useful, because its symptoms are a continuous variable (so small changes can be measured) and reversible. Evaluation of treatment efficacy therefore does not require monitoring of sporadic events such as opportunistic infections, as in most current AIDS clinical trials, but rather the measurement of improved performance on tests of brain function.
The second type of interaction among HIV, the brain, and behavior relates to the unique issues associated with multiple diagnoses, that is diagnosis of any combination of HIV, drug or alcohol abuse, and mental illness. This kind of multiple diagnosis is not uncommon, and it likely affects disease progression as well as treatment strategies. It is vitally important to recognize the interactive nature of HIV infection, substance use and abuse, and mental illness in order to appropriately intervene. This, too, requires a cross-disciplinary approach.
Drinking alcohol to excess has been shown to cause damage to the immune system (Kruger and Jerrells, 1992). It therefore seems reasonable to assume that alcohol consumption in significant amounts may also render an individual more vulnerable to HIV infection