Melatonin suppression by light in euthymic bipolar and unipolar patients

Arch Gen Psychiatry. 2000 Jun;57(6):572-9. doi: 10.1001/archpsyc.57.6.572.

Abstract

Background: Previous studies have suggested that bipolar patients are supersensitive to light suppression of melatonin and that this may be a trait marker for genetic vulnerability. The present study was an attempt to replicate and extend this observation. Propranolol hydrochloride effects were compared with light effects because of the documented influence of beta-adrenergic receptors on melatonin production. Nighttime levels of corticotropin and cortisol were also examined as potential trait vulnerability markers.

Methods: Melatonin levels in euthymic bipolar patients (n= 29) were tested before and after 500-lux light was administered between 2 and 4 AM and on a separate night in the dark. Results were compared with those of a group of patients with unipolar depression (n= 24) and with those of a group of non-psychiatrically ill control subjects (n= 50). Lithium effects and propranolol effects were tested in subgroups.

Results: No group differences were seen in light suppression among bipolar patients, unipolar patients, and controls; an analysis of the whole group did not reveal differences in propranolol effect, differences in corticotropin or cortisol levels, or evidence for a lithium effect. However, patients with bipolar I affective disorder showed the following: (1) significantly lower melatonin levels on the light night, at baseline and following light exposure; and (2) a later peak time for melatonin on the dark night.

Conclusions: The general hypothesis of increased light sensitivity in bipolar patients was not supported. However, melatonin secretion abnormalities were confirmed in the subgroup with bipolar I disorder. Further assessments of circadian rhythm disruption as a vulnerability marker in bipolar illness are indicated.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adrenocorticotropic Hormone / blood
  • Adult
  • Bipolar Disorder / blood*
  • Bipolar Disorder / diagnosis
  • Bipolar Disorder / genetics*
  • Circadian Rhythm / drug effects
  • Circadian Rhythm / genetics
  • Circadian Rhythm / physiology*
  • Depressive Disorder / blood*
  • Depressive Disorder / diagnosis
  • Depressive Disorder / genetics*
  • Female
  • Genetic Markers
  • Genetic Predisposition to Disease
  • Humans
  • Hydrocortisone / blood
  • Light*
  • Lithium / pharmacology
  • Male
  • Melatonin / blood*
  • Melatonin / metabolism
  • Middle Aged
  • Photic Stimulation
  • Propranolol / pharmacology
  • Radioimmunoassay

Substances

  • Genetic Markers
  • Adrenocorticotropic Hormone
  • Lithium
  • Propranolol
  • Melatonin
  • Hydrocortisone