Perception of the amount of drinking by others in a sample of 20-year-old men: the more I think you drink, the more I drink.

BACKGROUND The amount a person drinks can be influenced by their perception of drinking by others. AIM We studied whether perception of the amount of drinking by others (same age and sex) is associated with one's own current drinking, and the factors that are related to this perception. METHODS A random sample of drinkers (n = 404) from a census of 20-year-old Swiss men (n = 9686) estimated the percentage of others who drink more than they do. Using weekly alcohol consumption data of the census, we computed for each subject the percentage of individuals drinking more than they do. We compared the 'perceived' to the 'computed' percentage and classified the drinkers as overestimating or not drinking by others. We compared the alcohol consumption of those who overestimated drinking by others to those who did not, using analyses of variance/covariance. We used logistic regression models to evaluate the impact of age, education level, occupation, living environment and family history of alcohol problems on estimations of drinking by others. RESULTS Among the 404 drinkers, the mean (SD) number of drinks/week was 7.95(9.79); 45.5% overestimated drinking by others, while 35.2% underestimated it and 19.3% made an accurate estimation. The likelihood of overestimating increased as individual alcohol use increased. Those overestimating consumed more alcohol than those who did not; the adjusted mean number of drinks/week (SE) 11.45 (1.12) versus 4.50 (1.08), P < 0.0001. Except for current drinking, no other variables were significantly associated with overestimating. CONCLUSION This study confirms prior findings within selective student populations. It sets the stage for preventive actions, such as normative feedback based on social norms theory.