Long-term naturalistic follow-up of lithium augmentation: relevance to bipolarity

Whether bipolarity (unrecognized bipolar disorder) is related to the treatment response to lithium augmentation in antidepressant-refractory depression remains unclear. This study of responders and non-responders to lithium augmentation of 29 antidepressant-refractory patients with major depression, whom we had studied during 1995-1997, compared the bipolar diagnosis at the follow-up based on diagnostic confirmation after long-term follow-up.

Before being classified as stage 2 treatment-resistant depression, these patients had been treated adequately with at least two tricyclic or heterocyclic antidepressants from different pharmacological classes (a minimum of the equivalent of 150 mg of imipramine for 4 weeks). During 1995-1997, 29 patients received lithium augmentation. Their treatment responses were recorded. Mean follow-up was 8.0 years (range, 1-13 years). Bipolar conversion and full remission were evaluated.

After the long-term follow-up, diagnoses were changed to bipolar depression in 3 of 4 lithium responders and 3 of 25 lithium non-responders; lithium augmentation was more effective for unrecognized bipolar patients. Only the family history of bipolar disorder predicted subsequent bipolar conversion.

Treatment was not controlled in this naturalistic study, which had a small sample size.

Results of this long-term follow-up study suggest that bipolarity is related to a positive response to lithium augmentation in stage 2 treatment-resistant major depression. The family history of bipolar disorder suggests false unipolar depression, and therefore indicates lithium responders.