is an anorexigenic agent (appetite suppressant) that markedly decreases brain serotonin. Studies have shown 30-40 percent of autistic people have high levels of serotonin, one of the substances which help transmit impulses between brain cells. One case study in 1982 suggested that Fenfluramine significantly improved behaviour (Geller, Ritvo, Freeman, & Yuweiler, 1982). Further studies are conflicting, and most do not support this theory.