Phenylethylamine is an endogenous neuroamine conceptualized as the body's natural amphetamine. PEA has been suggested to play a role in the etiology of several neuropsychiatric disorders. Increased PEA turnover in phenylketonuria contributes to the pathophysiology of this condition. Depressed and chronic paranoid schizophrenic patients show decreased and increased PEA urinary excretion, respectively. Parkinsonian patients show decreased urinary PEA excretion. In animals, drugs that relieve or produce depression and parkinson result in increased or decreased brain PEA levels, respectively. PEA has been postulated to play a role in the etiology of migraine headache and aggression.