Longitudinal trajectories of non-medical use of prescription medication among middle and high school students.

The non-medical use of prescription medications has been identified as a major public health problem among youth, although few longitudinal studies have examined non-medical use of prescription medications in the context of other drug use. Previous cross-sectional studies have shown gender and race differences in non-medical use of prescription medications. It was hypothesized that (1) non-medical use of prescription medications increases with age, and (2) these increases will be stronger in magnitude among female and Caucasian adolescents. Changes in non-medical use of prescription medications across 4 years were examined and compared with changes in other drug use (e.g., alcohol and marijuana). Middle and high school students enrolled in 5 schools in southeastern Michigan completed web-based surveys at 4 annual time points. The cumulative sample size was 5,217. The sample ranged from 12 to 18 years, 61% were Caucasian, 34% were African American, and 50% were female. Using a series of repeated measures latent class analyses, the trajectories of non-medical use of prescription medications were examined, demonstrating a 2-class solution: (1) the no/low non-medical use of prescription medications group had low probabilities of any non-medical use of prescription medications across all grades, and (2) the any non-medical use of prescription medications group showed a roughly linear increase in the probability of non-medical use of prescription medications over time. The probability of any non-medical use of prescription medications increased during the transition from middle school to high school. Results from this longitudinal study yielded several noteworthy findings: Participants who were classified in the any/high non-medical use of prescription medications group showed a discontinuous pattern of non-medical use of prescription medications over time, indicating that non-medical use of prescription medications is a relatively sporadic behavior that does not persist over time. However, among the "any/high non-medical use of prescription medications" group the pattern of change over time varied by race/ethnicity, with Caucasians showing a clear increase in the probability of non-medical use of prescription medications over time compared to non-Caucasians. This study fills gaps in knowledge by examining non-medical use of prescription medications over time and provides important information about the course of non-medical use of prescription medications among adolescents.