Functional drug use defined: A latent class analysis

Background: Drug use is associated with consequences, however not all use is harmful. Functional drug users are persons with moderate, non-abusive drug use able to meet social expectations. We use latent class analysis to determine to what extent patterns of functional and non-functional drug use exist.

Methods: Data come from the IMPACT study in New York City. Our final model included measures of drug use behaviors (frequency of cocaine, crack and heroin use; use of non-prescribed opiates and club drugs; injection), drug use harms (interference with regular activities due to cocaine, crack or heroin use; failure to meet expectations due to alcohol use; overdoses; HIV and Hepatitis B serostatus) and social expectations (did not have enough money to buy food, and main source of income).

Results: Model fit statistics indicated a 5-class solution fit best. Class 1 was characterized as non-drug users, and class 2 as former-drug users. Participants in class 3 report low frequency of cocaine and crack use, low levels of interference from their use and moderate success meeting social expectations. Participants in class 4 report low frequency heroin use, and non-prescribed opiate use; a moderate number experience interference from their use and moderate success meeting social expectations. Class 5 were non-functional drug users reporting high frequency cocaine, crack and heroin use, use of non-prescribed opiates and club drugs, high levels of interference and failure to meet social expectations.

Conclusions: We find evidence of functional and non-functional drug use; identifying drivers of these patterns may improve population health.