Researchers investigated the prevalence of personality disorders among adolescents who were psychiatric inpatients and had one of three diagnoses: (1) those with major depression, (2) those with substance abuse, and (3) those with both major depression and substance abuse. The mean number of disorders was as follows: major depression M = 1.1, substance abuse M = 0.6, those with both conditions M = 2.1. The researchers reported, "The three study groups differed in the average number of diagnosed personality disorders, F(2,123) = 10.31, p