Low concentrations of serum tyrosine in neuroleptic-free schizophrenics with an early onset

The concentrations of serum tyrosine, phenylalanine and tryptophan have been determined in 23 male neuroleptic-free patients with schizophrenia and 28 male healthy control subjects. Tyrosine was significantly lower in neuroleptic-free patients with an early onset (starting before adulthood) than in healthy control subjects (p