Predictors of response to lithium and triiodothyronine augmentation of antidepressants in tricyclic non-responders.

Although both lithium and triiodothyronine (T3) augmentation strategies may be rapid, safe, and effective ways of treating patients who fail to respond to tricyclics, little is known about the clinical or biochemical correlates of response. We examined clinical and endocrine variables which distinguished T3 and lithium responders from each other and from non-responders in a post-hoc analysis of two studies involving 51 subjects who had received these augmentation strategies under double-blind conditions. Lithium non-responders were more severely depressed and had more insomnia and weight loss than responders. T3 responders could be distinguished from lithium responders by greater weight loss. There were no reliable clinical differences between T3 responders and non-responders. Thyroid function tests did not differ between any of the treatment or response groups. Our findings suggest that clinical but not endocrine variables may distinguish responders to these two augmentation strategies.