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A Circadian Signal of Change of Season in Patients With Seasonal Affective Disorder
Thomas A. Wehr, MD;
Wallace C. Duncan, Jr, PhD;
Leo Sher, MD;
Daniel Aeschbach, PhD;
Paul J. Schwartz, MD;
Erick H. Turner, MD;
Teodor T. Postolache, MD;
Norman E. Rosenthal, MD
Arch Gen Psychiatry. 2001;58:1108-1114.
Background In animals, the circadian pacemaker regulates seasonal changes in behavior
by transmitting a signal of day length to other sites in the organism. The
signal is expressed reciprocally in the duration of nocturnal melatonin secretion,
which is longer in winter than in summer. We investigated whether such a signal
could mediate the effects of change of season on patients with seasonal affective
disorder.
Methods The duration of melatonin secretion in constant dim light was measured
in winter and in summer in 55 patients and 55 matched healthy volunteers.
Levels of melatonin were measured in plasma samples that were obtained every
30 minutes for 24 hours in each season.
Results Patients and volunteers responded differently to change of season. In
patients, the duration of the nocturnal period of active melatonin secretion
was longer in winter than in summer (9.0 ± 1.3 vs 8.4 ± 1.3
hours; P = .001) but in healthy volunteers there was
no change (9.0 ± 1.6 vs 8.9 ± 1.2 hours;
P = .5).
Conclusions The results show that patients with seasonal affective disorder generate
a biological signal of change of season that is absent in healthy volunteers
and that is similar to the signal that mammals use to regulate seasonal changes
in their behavior. While not proving causality, this finding is consistent
with the hypothesis that neural circuits that mediate the effects of seasonal
changes in day length on mammalian behavior mediate effects of season and
light treatment on seasonal affective disorder.
From the Section on Biological Rhythms, Mood and Anxiety Disorders
Program, Intramural Research Program, National Institute of Mental Health,
Bethesda, Md (Drs Wehr, Duncan, Aeschbach, Turner, Postolache, and Rosenthal);
Psychiatric Institute, Columbia University, New York, NY (Dr Sher); and the
Veterans Administration Medical Center, Cincinnati, Ohio (Dr Schwartz). Dr
Turner is currently affiliated with the Mood Disorders Program, Portland VA
Medical Center, Portland, Ore.
Corresponding author and reprints: Thomas A. Wehr, MD, National Institute
of Mental Health, 10/3S231, 10 Center Dr MSC1390, Bethesda, MD 20892-1390.
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Arch Gen Psychiatry. 2001;58(12):1115-1116.
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