LACK OF ENHANCED RESPONSE TO REPEATED D-AMPHETAMINE CHALLENGE IN FIRST-EPISODE PSYCHOSIS - IMPLICATIONS FOR A SENSITIZATION MODEL OF PSYCHOSIS IN HUMANS

Behavioral sensitization is the process whereby intermittent stimulant exposure produces a time-dependent, enduring and progressively more r obust behavioral response., This process serves as a model for the dev elopment of psychosis, brit has been little studied in humans. The aut hors report results front a double-blind placebo-controlled study of r epeated d-amphetamine challenges in 13 patients with first-episode man ic or schizophrenic psychosis. Each patient received two daily doses o f d-amphetamine (0.25 mg/kg) separated by 48 hours that alternated wit h two daily doses of matched placebo. Symptoms (activity/energy level, mood, rate and amount of speech, and severity of psychosis) and eye-b link rates were measured hourly for 5 hours following drug administrat ion. In contrast to results from previous work in normal volunteers, n one of the measures demonstrated the progressive increase following th e second amphetamine dose as compared to the first dose that character izes sensitization. These results suggest that patients with psychosis are already maximally sensitized, so cannot exhibit progressive behav ioral enhancement following repeated stimulant challenges or that pati ents with psychosis do not sensitize. (C) 1997 Society of Biological P sychiatry.