Objective: To examine prospectively the natural course of bulimia nervosa (BN) and eating disorder not otherwise specified (EDNOS) and to test the effects of personality disorder (PD) comorbidity on the outcomes.

Method: Ninety-two female patients with current BN (N ¼ 23) or EDNOS (N ¼ 69) were evaluated at baseline enrollment in the Collaborative Longitudinal Personality Disorders Study (CLPS). Eating disorders (EDs) were assessed with the Structured Clinical Interview for DSM-IV Axis I Disorders. Personality disorders (PDs) were assessed with the Diagnostic Interview for DSM-IV PD (DIPD-IV). The course of BN and EDNOS was assessed with the Longitudinal Interval Follow-up Evaluation and the course of PDs was evaluated with the Follow-Along version of the DIPD-IV at 6, 12, and 24 months.

Results: Probability of remission at 24 months was 40% for BN and 59% for EDNOS. To test the effects of PD comorbidity on course, ED patients were divided into groups with no, one, and two or more PDs. Cox proportional regression analyses revealed that BN had a longer time to remission than EDNOS (p < .05). The number of PDs was not a significant predictor of time to remission, nor was the presence of Axis I psychiatric comorbidity or Global Assessment of Functioning scores. Analyses using proportional hazards regression with time-varying covariates revealed that PD instability was unrelated to changes in ED.

Conclusions: BN has a worse 24-month course (longer time to remission) than EDNOS. The natural course of BN and EDNOS is not influenced significantly by the presence, severity, or time-varying changes of co-occurring PDs, co-occurring Axis I disorders, or by global functioning.