Nonspecific factors and side effect complaints. Factors affecting the incidence of drowsiness in drug and placebo treated anxious and depressed outpatients.

Discriminant function analyses were applied to data obtained from anxious psychiatric outpatients treated with either chlordiazepoxide (n = 353) or placebo (n = 259) and depressed outpatients treated with either amitriptyline (n = 310) or placebo (n = 328), who had participated in controlled drug trials of 4 weeks' duration, in an attempt to identify factors associated with complaints of drowsiness made by these patients. Although the magnitude of the relationships between individual predictors and drowsiness was small, several factors emerged which had consistent impact across treatment groups. Predictors of complaints of drowsiness attributed to active drugs arose primarily from demographic attributes probably reflective of life style, and from illness and treatment history. In contrast, predictors of drowsiness attributed to placebo were almost exclusively confined to indices of the severity of several aspects of presenting symptomatology. In particular, more frequent complaints of drug-induced drowsiness were found among better educated individuals with an illness of long duration. Complaints of placebo-induced drowsiness were more common among patients with more severe emotional (phobic-obsessive) symptomatology and more frequent headaches and among those individuals in whom hypochondriasis was less severe.