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Melatonin Suppression by Light in Euthymic Bipolar and Unipolar Patients
John I. Nurnberger, Jr, MD, PhD;
Sherril Adkins, RN;
Debomoy K. Lahiri, PhD;
Aimee Mayeda, MD;
Kuolung Hu, MS;
Alfred Lewy, MD, PhD;
Aaron Miller, MD;
Elizabeth S. Bowman, MD;
Marvin J. Miller, MD;
N. Leela Rau, MD;
Carrie Smiley, RN;
Dawn Davis-Singh, BS
Arch Gen Psychiatry. 2000;57:572-579.
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 -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 nonpsychiatrically 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.
From the Department of Psychiatry, Indiana University School of Medicine (Drs Nurnberger, Lahiri, Mayeda, A. Miller, and Bowman and Mss Adkins, Hu, Smiley, and Davis-Singh), Department of Psychiatry, Roudebush Veterans Affairs Medical Center (Dr Mayeda), the Institute of Psychiatric Research, Larue Carter Hospital (Dr M. J. Miller), and Department of Psychiatry, Wishard Hospital (Dr Rau), Indianapolis, Ind; and the Department of Psychiatry, Oregon Health Sciences University, Portland (Dr Lewy).
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