The association between sniffing inhalants and injecting drugs

Abstract

There is evidence that the use of inhalants might prove to be a modifiable risk factor for intravenous (IV) drug use, or possibly an important vulnerability marker. However, this evidence has come from studies using samples of convenience, such as a mixture of psychiatric patients, felons, and their relatives. If there is a link between these two different forms of drug-using behaviors, then a statistical association should be found in epidemiologic studies with rigorous sampling procedures—even after statistical adjustment for plausible confounding variables such as sex, age, socioeconomic status, and the use of drugs such as marijuana. To probe this suspected causal association, we analyzed epidemiologic data from the 1990 National Household Survey on Drug Abuse sponsored by the National Institute on Drug Abuse. The population for this survey consisted of all household residents aged 12 years and older in the conterminous United States, with respondents selected by probability sampling. A total of 9,259 respondents completed the confidential self-report interview conducted by trained interviewers; 192 persons reported a history of injecting drugs for nonmedical reasons (e.g., to get high), and 9,067 reported never injecting drugs. As hypothesized, inhalant use was found to be associated with injecting drugs (relative odds [RO] = 11.8). After adjustment for sex, age, race, socioeconomic status, and use of marijuana, inhalant users still were 5.35 times more likely than nonusers to have injected drugs ( P < .001). Further, the odds of injecting drugs were exceptionally small among respondents who had used neither inhalants nor marijuana, and respondents using both marijuana and inhalants were an estimated 88.6 times more likely to have injected drugs (95% confidence interval [Cl] = 63.1 to 124.5); those using inhalants but not marijuana were an estimated 45.1 times more likely to have injected drugs (95% Cl = 28.1 to 75.8); the corresponding odds ratio was 18.5 for respondents who used marijuana but not inhalants (95% Cl = 13.3 to 25.8). Despite some methodologic limitations, this epidemiologic evidence strengthens the rationale for a more deliberate focus on inhalant use in future studies that seek to understand etiologic conditions giving rise to IV drug use and other forms of nonmedical drug-injecting—an important issue for drug dependence research, as well as research on human immuno-deficiency virus infection and acquired immune deficiency syndrome.