The Association between Changes in Peer Pressure and Changes in Alcohol and Cannabis Use: A Prospective Cohort Study among Men during Emerging Adulthood

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Introduction: Cross-sectional studies have shown that peer influence to use a substance is associated with increased rates of substance use, but there are few longitudinal studies of this relationship or studies investigating whether peer influence to not use substances is associated with decreases in rates of substance use. The present study looks at both directions of influence and compares alcohol with cannabis use. Methods: Two-wave longitudinal study, separated by 15.8 months; cross-domain coupling model to disentangle effects of peer influence and peer selection; GEE models to analyse changes in pressure to use and not to use alcohol or cannabis. A total of 6,528 young men from six mandatory military recruitment centres in Lausanne, Windisch and Mels in Switzerland completed at least one questionnaire at baseline (age at baseline: 20.00) or follow-up. Questionnaires were completed outside the army and independent of recruitment for military or social service. Volume of drinking, heavy episodic drinking, cannabis use frequency, and three items of the misconduct subscale of the Peer Pressure Inventory (pressure to use cannabis or not, pressure to drink or not, and pressure to get drunk or not) were measured. Results: Peer pressure and peer selection operated bidirectionally for alcohol use. For cannabis use, peer selection was about 5-times stronger than peer pressure. Increases in pressure to use a substance were associated with increased substance use and decreases in pressure with decreases in use. Conclusions: Peer pressure continues to operate after adolescence into emerging adulthood, but the strength of the effects of peer pressure and peer selection depends on the substance. Peer pressure may have putatively positive effects when pressure is towards non-use of a substance.