Illicit Drug Use During Travel: A Longitudinal Study of Risk in Emerging Adults

International travel by emerging adults is increasingly recognized as a context for experimentation with illicit drugs. This longitudinal study examined predictors of drug use trajectories among 249 young adults traveling to South America or Southeast Asia. Participants completed assessments before departure and after their return. Latent profile analysis identified three use trajectories: Stable Low (48.4%), Experimental Increasing (28.4%), and Consistently High (23.2%). Use of illicit substances such as cocaine and LSD increased markedly during travel in the Consistently High group. Higher novelty seeking and lower commitment to developmental goals predicted membership in this group, while elevated depressive symptoms predicted membership in the Experimental Increasing group, which showed a temporary escalation. These findings highlight the role of personality, motivation, and emotional vulnerability in shaping responses to permissive environments. This study contributes to international drug research by identifying at-risk youth and informing targeted prevention strategies in youth health, and public drug policy.