Substance use disorders and overweight/obesity in bipolar I disorder: preliminary evidence for competing addictions.

OBJECTIVE

This investigation was undertaken to explore the relationship between alcohol/illicit drug dependence and overweight/obesity in individuals with bipolar I disorder.

METHOD

The data for this analysis were procured from the Canadian Community Health Survey-Mental Health and Well-Being (CCHS) conducted by Statistics Canada in 2002. Bipolar I disorder was defined as persons screening positive for a lifetime manic episode using the World Mental Health 2000 version of the Composite International Diagnostic Interview (WMH-CIDI). Substance abuse and illicit drug dependence were determined using criteria commensurate with the DSM-IV-TR. Overweight and obesity were defined as a body mass index of 25.0 to 29.9 and greater than or equal to 30.0 kg/m(2), respectively.

RESULTS

The total sample comprised 36,984 individuals (>or= 15 years old) screening positive for a lifetime manic episode. Subgroup analysis indicated that overweight/obese bipolar individuals had a significantly lower rate of substance dependence than the normal weight sample (13% vs. 21%, p < .01). Conversely, bipolar individuals who screened positive for substance dependence had a lower rate of overweight/obesity when compared with non-substance-dependent bipolar respondents (39% vs. 54%, p< .01). The inverse association between the presence of these 2 co-morbid conditions in bipolar I disorder continued to be statistically significant in multivariate analysis (OR = 0.57, 95% CI = 0.34 to 0.95, p < .05).

CONCLUSION

An inverse relationship between the presence of comorbid overweight/obesity and substance use disorders was observed in bipolar I disorder. These results suggest that comorbid addictive disorders (i.e., substance use and compulsive overeating) may compete for the same brain reward systems.