Impact of anxiety disorder comorbidity on quality of life in euthymic bipolar disorder patients: differences between bipolar I and II subtypes.

Background: Few studies investigated the impact of anxiety disorder comorbidity on health-related quality of life (HRQoL) of bipolar patients and none examined bipolar subtypes differences. The aim of the study was 1) to determine comorbidity rates for anxiety disorders in euthymic bipolar subjects, comparing bipolar type I and II disorders (BDI and BDII), and 2) to compare within each group HRQoL measures in subjects with and without anxiety comorbidity.
Methods: Comorbidity was evaluated through the SCID-I; HRQoL was assessed using the 36-Item Short-Form Health Survey (SF-36). All subjects were euthymic since at least 2 months, as confirmed by a HAM-D <8 and a YMRS <6. A comparison was made for SF-36 scores between subjects (all bipolars, BDI and BDII) with and without anxiety disorders.
Results: 105 patients were enrolled: 44 with BDI and 61 with BDII. Current and lifetime anxiety disorders comorbidities were 32.4% and 41.0% for all bipolars, 31.8% and 40.9% for BDI and 32.8% and 41.0% for BDII. BDI patients differed in several SF-36 domains from BDII subjects, which reported a poorer HRQoL. A current and lifetime comorbid anxiety disorder was associated with a poorer HRQoL considering all bipolars; when examining separately BDI and II subjects, however, the deleterious effect was restricted to BDI patients.
Limitations: The cross-sectional assessment of HRQoL, the generic instrument used (SF-36) and the small sample size.
Conclusions: Our study confirms the high comorbidity rates for anxiety disorders in bipolar subjects and provides evidence that anxiety comorbidity impacts HRQoL in subjects with BDI and not BDII.