Do eating disorders co-occur with personality disorders? Comparison groups matter.

OBJECTIVE To assess and compare lifetime rates of occurrence of eating disorders (ED) with four Axis II personality disorders (PD) and with major depressive disorder (MDD) without PD. The eating disorders met criteria outlined in the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). METHOD Six hundred sixty-eight patients recruited for the Collaborative Longitudinal Personality Disorders Study (CLPS) were reliably assessed with the Structured Clinical Interview for DSM-IV Axis I Disorders and the Diagnostic Interview for DSM-IV Personality Disorders. The distribution of ED diagnoses was compared among four PD study groups (schizotypal, borderline, avoidant, obsessive-compulsive) and a fifth study group with MDD without any PD. RESULTS The distribution of lifetime diagnoses of anorexia nervosa (N = 40), bulimia nervosa (N = 56), and eating disorder not otherwise specified (N = 118) did not differ significantly across the five study groups, between the MDD group versus all PD groups, and among the four PD study groups. CONCLUSIONS ED diagnoses did not differentially co-occur significantly across common Axis I and II disorders. The pattern of ED lifetime co-occurrence rates demonstrates the powerful influence of base rates and highlights that declarations of comorbidity demand significant variations from base-rate patterns.