This study contributes to a growing body of literature documenting the clinical significance of eating disorder symptoms in patients with bipolar spectrum disorders. Consistent with previous research (7
), we found a positive association between lifetime eating disorder co-morbidity and obesity and current illness severity in bipolar patients. Moreover, the present findings extend previous investigations by demonstrating that eating disorders are associated with a higher number of depressive episodes and increased rates of other psychiatric co-morbidities, particularly anxiety disorders, in this group. Elevated rates of additional psychiatric co-morbidity in patients with 2 versus 1 presenting disorder have been documented in a number of psychiatric populations (e.g., 20
). Nevertheless, given that both obesity and anxiety co-morbidity have been shown to correlate with indicators of poor prognosis in bipolar patients (e.g., delayed response to treatment, shorter time to recurrence) (22
), future studies are needed to determine the impact of aberrant eating on the clinical course of bipolar disorder and its treatment. In addition, research to tease apart the temporal and pathophysiological relationships among eating disorder symptoms, obesity, mood disorder history, and other psychiatric co-morbidity seems warranted.
The present study is the first to evaluate systematically the cognitive correlates of disordered eating in patients with bipolar spectrum disorders. Although DSM-IV
diagnostic criteria for AN and BN require overvaluation of eating, weight or shape, no study of which we are aware has documented the characteristics or severity of the cognitive aspects of eating disturbance in bipolar patients. Our results indicate that eating disorder co-morbidity in bipolar patients is not limited to the behavioral features of aberrant eating (i.e., binge eating, purging, dietary restriction). Indeed, even after controlling for BMI and current bipolar illness severity, patients with a lifetime history of clinically significant eating disturbance endorsed significantly more eating (e.g., eating in secret, guilt about eating), weight (e.g., desire to lose weight), and shape (e.g., feelings of fatness) concerns during the past month than did patients with no history of a threshold or subthreshold eating disorder. EDE scores in patients with lifetime eating disorder co-morbidity also were higher than established community norms for this measure (5
). These findings highlight the need for more careful evaluation of the full range of eating disorder psychopathology in patients with bipolar spectrum disorders. In light of evidence suggesting that the cognitive correlates of disordered eating are amenable to both psychotherapeutic and pharmacologic interventions (25
), the present findings also may have implications for the treatment of patients with co-occurring eating disorders and bipolar disorder.
One somewhat surprising finding of the current study is the relatively high percentage of male bipolar patients (i.e., 25.9%) with a lifetime history of clinically significant eating disturbance. Previous research has indicated that eating disorders are significantly more common among female bipolar patients as compared to males (27
), a finding that is consistent with prevalence estimates from epidemiologic studies (28
). One explanation for our discrepant results concerns the elevated rate of threshold and subthreshold BED in the present sample relative to rates of AN or BN. Epidemiologic research has indicated that rates of recurrent binge eating in the absence of inappropriate compensatory behaviors are comparable in males and females (30
). Moreover, there is some evidence that subthreshold binge eating disorders are more prevalent in men as compared to women. For example, using data from the National Comorbidity Survey replication, Hudson and colleagues (29
) found that the lifetime prevalence of subthreshold BED (i.e., twice weekly binge eating for at least 3 months in the absence of compensatory behaviors, distress, or other features associated with BED) was 3 times higher in males versus females; in contrast, lifetime rates of threshold-level eating disorders were between 1.75 (for BED) and 3 (AN and BN) times higher in women.
The current findings must be interpreted in light of the limitations of this research. First, and most significantly, participants were enrolled in a clinical trial (the BDCP) and responded to advertisements for an ancillary study; therefore, they may not be representative of the population of individuals with bipolar spectrum disorders. Although one strength of the BDCP is that it employs broad inclusion criteria and targeted recruitment strategies designed to ensure enrollment of patients typically under-represented in clinical trials (e.g., Blacks, individuals age ≥ 65 years), it is well-known that individuals presenting for treatment are more likely than are those in the community to have more than one psychiatric disorder (31
). Thus, rates of eating disorder psychopathology and other psychiatric co-morbidity in the present sample are likely higher than would be documented in an epidemiologic survey. Second, the sample size was small, particularly in the ED group, which may limit the stability and generalization of the findings. Future studies with larger sample sizes are needed to: 1) replicate the current research; 2) evaluate the clinical significance of threshold versus subthreshold eating disorder co-morbidity in patients with bipolar spectrum disorders; and 3) examine differences between bipolar patients with AN versus BN and BED on indices of illness burden. Third, the present study focused exclusively on adult bipolar patients. Future research is needed to document the prevalence and correlates of eating disorder symptomatology in children and adolescents with bipolar disorder.
In conclusion, lifetime eating disorder co-morbidity was associated with increased BMI and current illness severity, a greater number of depressive episodes, and more psychiatric co-morbidity in a well-defined sample of patients with bipolar spectrum disorders. Bipolar patients with co-occurring eating disorders also endorsed more cognitive correlates of disordered eating than did patients with no history of clinically significant eating disturbance. These findings highlight the need for a renewed emphasis on the evaluation and management of weight and eating in the mood disorders. In particular, our research suggests that eating disorder co-morbidity may be a marker for increased symptom load and illness burden in bipolar disorder. Given the abundance of recent work documenting the convergence of medical and psychiatric co-morbidities in bipolar patients (e.g., 32
), future research is needed to elucidate the endopathology of increased symptom load in this population.