Neuropeptide Y (NPY) was measured in postmortem brain tissue from victims of suicide & from individuals dying a sudden natural or accidental death. Concentrations of NPY-immunoreactivity were significantly lower in postmortem frontal cortex & caudate nucleus from suicide victims compared with age-matched controls. The authors suggest there is a deficit in the brain NPY system leading to region-specific reductions in peptide concentrations in subjects who have a history of depression. (45 refs.)