Serum melatonin in relation to clinical variables in patients with major depressive disorder and a hypothesis of a low melatonin syndrome

Abstract

Maximum nocturnal serum melatonin level (MT_max) in relation to some clinical variables was studied in 32 patients with a major depressive episode and in 33 healthy subjects with reference to the outcome of the dexamethasone suppression test (DST). Significant regressions were found between MT_max levels and clinical rating scores in CPRS, interpreted as retardation symptoms. Four healthy subjects with disposition for dysthymic reactions had subnormal MT_max levels, which differed from MT_max levels in subjects without such disposition. Patients but not the healthy subjects, who reported parental loss before 17 years of age, had subnormal MT_max levels and differed from patients with no reported parental loss. Patients with no reported suicidal behaviour in clinical history had significantly lower MT_max levels than patients with reported suicide attempts. No relations were found between low MT_max levels and diagnoses, duration of illness, reported inheritance for depressive illness or sleep disturbances. A hypothetical low melatonin syndrome in depression is proposed: 1) low nocturnal melatonin, 2) abnormal dexamethasone suppression test, 3) disturbed 24-h rhythm of cortisol, 4) less pronounced daily and annual cyclic variation in depressive symptomatology.