Five manic patients were treated with chlorpromazine hydrochloride (CPZ), then with L-tryptophan (LTP), and five with LTP first, then CPZ, in a double-blind, placebo-controlled crossover study. LTP was slightly superior to CPZ in all regards. Mania and depression may be linked by a central indoleamine deficit.
Prange AJ, Wilson IC, Lynn CW, Alltop LB, Stikeleather RA. L-Tryptophan in ManiaContribution to a Permissive Hypothesis of Affective Disorders. Arch Gen Psychiatry. 1974;30(1):56-62. doi:10.1001/archpsyc.1974.01760070040006