Background: Most alcoholism research in the U.S. uses convenience samples of treated alcoholics. The findings from treated samples have traditionally been applied to all alcoholics, including the 75% of alcoholics who are untreated. Improper generalization from select samples to an entire population is called 'Berkson's fallacy'. We compared untreated versus treated alcoholics, in order to ascertain whether both groups belonged to the same population with regard to psychiatric comorbidity.
Methods: We compared psychiatric comorbidity in 1) active treatment-naive alcoholics (TNA; n=86) 2) treated long-term abstinent alcoholics (TAA; n=52) and 3) non-alcoholic controls (NAC;n=118). We examined lifetime and current diagnoses, lifetime symptom counts, and psychological measures in the anxiety, mood and externalizing disorder domains.
Results: TNA did not differ from NAC in psychiatric diagnosis rates, were abnormal compared to NAC on all psychological measures, had more externalizing symptoms than NAC, and showed a strong trend for men to have more symptoms in the mood and anxiety domains. TAA compared to TNA had higher diagnosis rates (all domains), symptom counts (all domains), and psychological measures of deviance proneness, but were comparable to TNA on anxiety and mood psychological measures.
Conclusions: The abnormal thinking (psychological measures) in TNA (versus NAC) does not extend to behavior (symptoms) to the degree that it does in TAA. These results underline the importance of the use of subdiagnostic measures of psychiatric comorbidity in studies of alcoholics. The finding of lesser comorbidity in TNA versus TAA confirms the presence of Berkson's fallacy in generalizing from treated samples to all alcoholics.