IMPACT OF SUPPRESSION OF THYROXINE ON FOLATE STATUS DURING ACUTE ANTIDEPRESSANT THERAPY

Antidepressant response is associated with a rise in red cell folate ( RCF) and a reduction in thyroxine (T4). Since T4 levels may directly i nfluence folate status, it is possible that the increase in folate wit h recovery results from the decline in T4. To examine the possible rol e of thyroid hormones in the observed change in folate status during a ntidepressant therapy, T4, tri-iodothyronine (T3) or placebo was given in a double-blind fashion to 25 depressed subjects at the initiation of standard antidepressant treatment. Folate levels and mood [using th e Hamilton Rating Scale for Depression (HAMD), Montgomery-Asberg Depre ssion Rating Scale (MADRS) and Beck Depression Inventory (BDI)] were m easured at baseline and following 4 weeks of therapy. Using MANOVA for repeated measures, there was a significant interaction between respon se status and time for vitamin and hormone levels. Univariate analysis confirmed that response was associated with a significant change in r ed cell folate, but not a significant change in T4 or T3. The mean cha nge in RCF across the 4-week trial was significantly greater in the 14 responders than the 11 non-responders. Change in RCF, and not change in T4 or T3, was significantly correlated with change in HAMD and cont ributed significantly to the variance in change in HAMD. These results suggest that change in RCF is closely tied to response to antidepress ant treatment, and this effect is not inhibited by exogenous administr ation of thyroid hormones or the changes in T4 that the exogenous horm ones produce. These findings support the possible role of folate, inde pendent of thyroid function, in the modulation of mood. (C) 1998 Elsev ier Science Ireland Ltd. All rights reserved.