Can improvement in well-being and functioning be distinguished from depression improvement in antidepressant clinical trials?

The Inventory of General Life Functioning (GLF), a self-evaluation scale for patients, was developed for use in the National Institute of Mental Health Treatment of Depression Collaborative Research Program. The scale was designed to evaluate patient general well-being and functioning, areas not adequately covered by standard depression scales. We used the patient self-report version of the GLF in two imipramine-controlled clinical trials during the development of the antidepressant venlafaxine. In these double-blind studies, outpatients with depression received placebo (n = 158), venlafaxine (n = 152), or imipramine (n = 149) for up to 6 weeks. We examined the internal consistency and factor structure of the GLF, its correlation with standard depression rating scales, and its sensitivity to differential treatment effects. We found the scale to be internally consistent and moderately correlated with physician-rated measures of depression. A reported two-factor structure (general well-being and functioning) was evaluated by factor analysis. When analyses were restricted to patients who completed at least 4 weeks on therapy, the GLF displayed sensitivity to differential treatment effects. The GLF total and factor subscales demonstrated the superiority of an active therapy (venlafaxine) to placebo; the GLF factor and a 7-item subscale using only items derived from Dupuy's psychological general well-being index (PGWB) demonstrated an advantage for one active therapy (venlafaxine) over another (imipramine). The GLF is a useful complement to the standard depression rating scales because it may assess additional dimensions of the depressive syndrome.