Mood symptoms, functional impairment, and disability in people with bipolar disorder: specific effects of mania and depression.

OBJECTIVE

To examine the relationship between changes in mood symptoms and changes in functioning or disability in people treated for bipolar disorder.

METHOD

This study was a secondary analysis of data from 441 patients enrolled in a randomized trial of a care management and psychoeducational intervention for bipolar disorder (diagnosed according to DSM-IV). Study participants were enrolled between August 1999 and October 2000, and follow-up data were collected until October 2001. Five in-person assessments spaced 3 months apart included structured assessment of current mood symptoms (using the Structured Clinical Interview for DSM-IV), the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) functional status questionnaire, and questions regarding days of disability during the past 3 months. Repeated-measures analyses examined the associations between each outcome measure and severity of mood symptoms. Additional analyses separated variability in mood symptoms into between-person variation (average symptom severity, or trait effects) and within-person variation (change from average symptom severity, or state effects).

RESULTS

Severity of depression symptoms showed a strong and consistent association with all 4 measures of impairment and disability (SF-36 Role-Emotional score, SF-36 Social Function score, days unable to perform household responsibilities, days disabled from other activities; p < .001 for all comparisons). These associations all remained highly significant (p < .001) after adjustment for co-occurring symptoms of mania. Severity of mania/ hypomania symptoms also showed significant association with all disability measures (p < .001 for all comparisons), but these associations were weaker after adjustment for co-occurring symptoms of depression (p < .001 for SF-36 Role-Emotional score, p = .004 for SF-36 Social Function score, p = .069 for days unable to perform household activities, p = .049 for days disabled from other activities). In analyses focused on within-person variation, change in depression was again strongly related to all measures of impairment and disability (p < .001 for all comparisons). After adjustment for co-occurring depression, change in mania/hypomania was not consistently associated with measures of impairment or disability (p = .02 for SF-36 Role-Emotional score; p > .40 for all other comparisons).

CONCLUSIONS

Among people treated for bipolar disorder, modest changes in severity of depression are associated with statistically and clinically significant changes in functional impairment and disability. In contrast, changes in severity of mania or hypomania are not consistently associated with differences in functioning. Conventional measures of functioning, however, may not be sensitive to the effects of mania symptoms.