Effects of acute tryptophan depletion on mood and suicidal ideation in bipolar patients symptomatically stable on lithium

Background Previous studies suggest that brain serotonin neurotransmission may mediate the actions of lithium carbonate. Acute tryptophan depletion reduces brain serotonin and allows the study of this neurotransmitter in patient groups. Aims To examine the effects of acute tryptophan depletion on mood and suicidal ideation in bipolar patients who were symptomatically stable on lithium. Method Nineteen subjects satisfying DSM - IV criteria for bipolar I disorder participated in a within-subject, double-blind, placebo-controlled random-order crossover study. Symptoms were evaluated following acute tryptophan depletion. which was induced by a 100 g amino acid drink following an overnight fast. Results Plasma tryptophan fell significantly after the depleting drink, but not after the control drink (P < 0.05, paired t-test, mean reduction 83%). No significant changes in mood or suicidality scores were recorded after acute tryptophan depletion. Conclusions Acute tryptophan depletion does not reverse lithium's effects on mood and suicidality in bipolar disorder. Declaration of interest Funded by the Theodore and Vada Stanley Foundation.