Such arguments have been repeatedly contradicted. Compelling evidence against the risk-AIDS hypothesis has come from cohort studies of high-risk groups in which all individuals with AIDS-related conditions are HIV-antibody positive, while matched, HIV-antibody negative controls do not develop AIDS or immunosuppression, despite engaging in high-risk behaviors.

In a prospectively studied cohort in Vancouver (Schechter et al., 1993a), 715 homosexual men were followed for a median of 8.6 years. Among 365 HIV-positive individuals, 136 developed AIDS. No AIDS-defining illnesses occurred among 350 HIV-negative men despite the fact that these men reported appreciable levels of nitrite use, other recreational drug use, and frequent receptive anal intercourse. The average rate of CD4+ T cell decline was 50 cells/mm3 per year in the HIV-positive men, while the HIV-negative men showed no decline. Significantly, the decline of CD4+ T cell counts in HIV-positive men and the stability of CD4+ T cell counts in HIV-negative men were apparent whether or not nitrite inhalants were used. There were 101 AIDS-related deaths among the HIV-seropositive men, including six unrelated to HIV infection. In the seronegative group, only two deaths occurred: one heart attack and one suicide. In this study, lifetime prevalences of risk behaviors were similar in the 136 HIV-seropositive men who developed AIDS and in the 226 HIV-seropositive men who did not develop AIDS: use of nitrite inhalants, 88 percent in both groups; use of other illicit drugs, 75 percent and 80 percent, respectively; more than 25 percent of sexual encounters involving receptive anal intercourse, 78 percent and 82 percent, respectively. Among HIV-seronegative men (none of whom developed AIDS), the lifetime prevalences of these behaviors were somewhat lower, but substantial: 56 percent, 74 percent and 58 percent, respectively.

Similar results were reported from the San Francisco Men's Health Study, a cohort of single men recruited in San Francisco in 1984 without regard to sexual preference, lifestyle or serostatus (Ascher et al., 1993a). During 96 months of follow-up, 215 cases of AIDS had occurred among 445 HIV-antibody positive homosexual men, 174 of whom had died. Among 367 antibody-negative homosexual men and 214 antibody-negative heterosexual men, no AIDS cases and eight deaths unrelated to AIDS-defining conditions were observed. The authors found no overall effect of drug consumption, including nitrites, on the development of Kaposi's sarcoma or other AIDS-defining conditions, nor an effect of the extent of the participants' drug use on these conditions. A consistent loss of CD4+ T cells was limited to HIV-positive subjects, among whom there was no discernible difference in CD4+ T cell counts related to drug-taking behavior. Among HIV-seronegative men, moderate or heavy drug users had higher CD4+ T cell counts than non-users.

Observational studies of HIV-infected individuals have found that drug use does not accelerate progression to AIDS (Kaslow et al., 1989; Coates et al., 1990; Lifson et al., 1990; Robertson et al., 1990). In a Dutch cohort of HIV-seropositive homosexual men, no significant differences in sexual behavior or use of cannabis, alcohol, tobacco, nitrite inhalants, LSD or amphetamines were found between men who remained asymptomatic for long periods and those who progressed to AIDS (Keet et al., 1994). Another study, of five cohorts of homosexual men for whom dates of seroconversion were well-documented, found no association between HIV disease progression and history of sexually transmitted diseases, number of sexual partners, use of AZT, alcohol, tobacco or recreational drugs (Veugelers et al., 1994).

Similarly, in the San Francisco City Clinic Cohort, recruited in the late 1970s and early 1980s in conjunction with hepatitis B studies, no consistent differences in exposure to recreational drugs or sexually transmitted diseases were seen between HIV-infected men who progressed to AIDS and those who remained healthy (Buchbinder et al., 1994).

Because many children with AIDS are born to mothers who abuse recreational drugs (Novick and Rubinstein, 1987; European Collaborative Study, 1991), it has been postulated that the mothers' drug consumption is responsible for children developing AIDS (Duesberg, 1987-1994). This theory is contradicted by numerous reports of infants with AIDS born to women infected with HIV through heterosexual contact or transfusions who do not use drugs (CDC, 1995a). As noted above, the only factor that predicts whether a child will develop AIDS is whether he or she is infected with HIV, not maternal drug use.