Longitudinal changes in methamphetamine and cocaine use in untreated rural stimulant users: racial differences and the impact of methamphetamine legislation.

AIMS To examine how race and methamphetamine legislation are associated with changes in cocaine and methamphetamine use among untreated rural stimulant users. DESIGN A longitudinal study of stimulant users identified through respondent-driven sampling. SETTING Rural areas of three US states. PARTICIPANTS Participants at baseline were current users of methamphetamine and/or cocaine. MEASURES Self-reports of methamphetamine, crack cocaine and powder cocaine use were assessed at 6-month intervals over a 2-year period. Generalized estimating equations were performed to account for correlations between the repeated measurements. FINDINGS Compared to whites, African Americans were much more likely to use crack cocaine, equally likely to use powder cocaine and much less likely to use methamphetamine. Both whites and African Americans reduced their consumption of methamphetamine and both forms of cocaine over 2 years. Exposure to laws restricting the purchase of over-the-counter cold medications containing methamphetamine precursors was not associated with methamphetamine use, but associated with a slight rise in powder and crack cocaine use. CONCLUSIONS The study yielded disconcerting as well as promising findings regarding the natural history of stimulant use in rural areas. Of some concern is that methamphetamine precursor laws were correlated with increased cocaine consumption, diminishing their net public health benefits. However, despite its insurgence in rural areas of the United States, very few African Americans have initiated methamphetamine use. Regardless of race, many stimulant users stopped using cocaine and methamphetamine without formal substance abuse treatment over 24 months.