Pineal melatonin in schizophrenia: a review and hypothesis.

It has long been suggested that abnormal functions of the pineal gland may be implicated in the pathophysiology of schizophrenia. We present evidence proposing that diminished melatonin secretion may be associated with the pathophysiology of a subgroup of schizophrenic patients characterized by cerebral atrophy and ventricular enlargement, negative symptoms, impaired cognitive and psychosexual development, onset at pubescence, poor response to neuroleptic medication, and possible increased risk of extrapyramidal symptoms. This view holds that a subnormal plasma melatonin level may be a marker of a subgroup of schizophrenia and may also denote a specific genetic susceptibility.