Patients with eating disorders exhibit high rates of psychiatric comorbidity and the number of comorbid psychiatric disorders is high. The treatment of co-occurring psychiatric problems in eating disordered patients is essential for good clinical management and the outcome of treatments. Higher rates of comorbidity often mean greater severity, treatment resistance and poor outcomes in eating disorders. The most prevalent Axis I disorders seem to be mood and anxiety disorders, alcohol and substance abuse, and bipolar disorder. Axis II disorders are also common. At least 80% of anorexia nervosa (AN) or bulimia nervosa (BN) patients have at least one additional psychiatric disorder over their lifetime. Mood disorders are very common among patients with AN. Major depressive disorder occurs in 50-70% of AN patients. Bulimic patients have 52-75% affective disorder, with 63% having major depression. Lifetime prevalence rates of major depression in BN are 50-65%.
Among study samples with restricting and binging /purging anorexia nervosa, prevalence rates of any anxiety disorder are found to be between 24% and 71%, respectively. Among patients with BN prevalence rates for any anxiety disorder, social phobia, generalised anxiety disoder (GAD) or panic disorder are reported to be 36%, 17%, 12% and 10% respectively. The approximate rates of any anxiety disorder in BN are reported to be between 57 and 75 %.
Thirty-five percent of restricting AN patients have obsessive compulsive disorder (OCD) and binging/purging AN patients have 44% OCD. BN patients have comorbid OCD 40% of the time. Lifetime prevalence rates of substance abuse in AN ranged from 12% to 18% and in BN the rates ranged from 30% to 70%. The results of clinical studies indicate that patients with BPD have higher rates of eating disorders compared with the general population. Rates of lifetime BPD in eating disorders patients are variable but higher than rates of BPD in the general population. Among eating disorder patients post-traumatic stress disorder rates were found between 8% to 11%.