Clinical and neurochemical effect of acute tryptophan depletion in unaffected relatives of patients with bipolar affective disorder.

Background: The lowering of mood induced by an acute tryptophan depletion (ATD) has been proposed as a candidate endophenotype for the vulnerability to manic-depressive illness. This study tests this hypothesis in relatives of probands from well-characterized multiplex families affected with bipolar affective disorder (BAD).

Methods: In a double-blind, crossover design, 20 unaffected relatives (URs) and 19 control subjects received either a 100-g amino acid (AA) drink devoid of tryptophan or a placebo, respectively.