Substance use disorders in outpatients with bipolar disorder and pain complaints.

Introduction: Pain and substance use disorders (SUDs) are common in bipolar disorder (BD), yet the associations between these comorbid conditions are poorly understood. Our hypotheses were: (1) the frequency of SUDs may vary according to pain intensity in individuals with BD, (2) individuals with BD, pain and SUDs may have specific characteristics, and (3) clinical variables could explain the associations between pain and SUDs.

Method: We included outpatients from the FACE-BD cohort with a lifetime diagnosis of BD type I or II. Current pain was categorized using one item of the EQ-5D-5L scale as "no pain", "mild pain", "moderate pain", and "severe or extreme pain". Associations between pain level and other variables were tested using bivariate analyses, while multiple regression was conducted to characterize individuals with BD, pain and relevant SUDs. Finally, path analysis was performed to examine whether clinical variables could explain the associations between pain and relevant SUDs.

Results: Among the 1897 BD participants, 927 reported any pain (48.9 %). Among SUDs, higher pain levels were only associated with a history of lifetime alcohol use disorder (AUD). Only individuals with both AUD and moderate to extreme pain had a greater risk of having a history of lifetime anxiety disorder and panic disorder. In path analysis, the association between lifetime AUD and pain was partly mediated by current levels of depression, anxiety, and affective lability.

Conclusion: Our study highlights multiple associations in individuals with BD between the intensity of reported pain and history of lifetime AUD.