Treated and treatment-naive alcoholics come from different populations.

In most research on alcoholism, convenience samples of individuals who have been in some type of treatment are used. Berkson's fallacy results when the associations found in studies of select samples are incorrectly presumed to apply to all alcoholics (i.e., including untreated alcoholics in the general population). In the current study, we examined whether treated and untreated alcoholics have similar early alcohol use histories by comparing abstinent alcoholics (treated and sober at least 6 months) with treatment-naive alcoholics (active drinkers). We studied 14 pairs of women and 25 pairs of men matched on the age at which they first met criteria for heavy alcohol use (women, 80 drinks per month; men, 100 drinks per month). The timeline follow-back interview method was used to gather retrospective alcohol use information. Alcohol dose and duration of use were subsequently computed for two intervals: (1) time between the person's first drink and date at which the person met criteria for heavy drinking and (2) period between when criteria for heavy drinking were met and current age of the treatment-naive person from each pair. During the period before the matching "heavy drinking" criteria were met, alcohol dose did not differ between groups. In the period after criteria for heavy alcohol use were met, in comparison with treatment-naive alcoholics, the treated alcoholics had higher average and peak alcohol doses. We rejected the hypothesis that the treatment-naive alcoholics and the treated alcoholics have similar alcohol use trajectories over time, with the treatment-naive sample simply being observed earlier in its alcohol use histories. Instead, we concluded that the two groups come from different populations with regard to alcohol use. In fact, the treated alcoholics had alcohol doses more than 50% higher than those of treatment-naive alcoholics in the years just after they began drinking heavily. This finding supports the suggestion that results from studies of alcoholics in treatment or after treatment (i.e., most studies of alcoholics) cannot be generalized to untreated individuals (who make up the majority of alcoholics).