Walshaw PD, et al. - The first comparative double-blind, placebo-controlled trial of levothyroxine (L-T₄) and triiodothyronine (T₃) as adjunctive treatments in rapid cycling bipolar disorder was described. Thirty-two treatment-resistant, rapid cycling patients who had failed a trial of lithium were randomized into three treatment arms: L-T₄, T₃, or placebo. Results provide support for the beneficial effect of adjunctive L-T₄ in relieving resistant depression, reducing time in mixed states and increasing time euthymic. No statistically significant evidence of benefit in terms of reducing the time spent in disturbed mood states was noted with adjunctive T₃ over placebo.