Background: Understanding the complex influence of peers on young adult substance use is an important component of intervention research and is challenging methodologically. The false consensus theory suggests that individual perceptions of peer substance use are biased, such that individual’s falsely attribute their own substance use behaviors onto their peers.
Methods: The current study tested this theory with 39 young adults with a mean age of 20 who met cannabis use disorder criteria. Index participants recruited three of their close friends for a sample of 156. Index participants reported their past 30-day cannabis and alcohol use, and their perceptions of their friends’ use. Indexes’ friends also reported their use of cannabis and alcohol.
Results: Results indicated that index participants were very accurate in their perceptions of the frequency of their friends’ cannabis (r = .84, p <0.01) and alcohol (r = .78, p <0.01) use. Simple linear regression models predicted friends’ actual cannabis and alcohol use based on indexes’ perceptions of friends’ use, controlling for indexes’ substance use. Indexes’ perceptions of friends’ cannabis use strongly predicted friend’s actual use (β = 0.80, p <0.01, adj-R2 = 0.67). Indexes’ perceptions of friends’ alcohol use also predicted friends’ actual use (Î² = 0.66, p <0.01, adj-R2 = 0.62). Indexes own substance use did not predict peer use in both models.
Conclusions: Results challenge the false consensus theory, demonstrating the accuracy of young adults’ knowledge of their friends substance use, indicating that perceptions are more predictive than individual use for determining the frequency of peer substance use.