Predictors of response to lithium augmentation in tricyclic antidepressant-resistant depression

Background: The efficacy of lithium augmentation in therapy-resistant depression has been shown in a series of well-designed, placebo-controlled studies. However, little is known about the predictors of a good response to this treatment strategy. Methods: We retrospectively examined the predictive value of 20 demographic, clinical, biochemical and endocrinological variables using a two-step logistic regression. Seventy-one in-patients with depression refractory to tricyclic antidepressants had received lithium augmentation as part of a standardised treatment protocol. Results: Within 4 weeks 37 patients (52%) responded to lithium augmentation. Five variables with predictive value were found. Responders were more severely depressed according to the Bech–Rafaelsen Melancholia Scale. The duration of their index episode was shorter. Triiodothyronine serum levels were lower and neuroleptic co-medication and co-diagnosis of personality disorder were less frequent. Limitations: This was an open, retrospective study. Conclusions: Severity of depression is a predictor of response to lithium augmentation. This result conflicts with recent studies but is similar to results found in studies of other pharmacological antidepressant strategies.