Does neuroimmune dysfunction mediate seasonal mood changes in winter depression?
BACKGROUND
Animal studies have demonstrated seasonal changes in immune function mediated by nocturnal melatonin duration as a biological signal for photoperiod. Recent research has highlighted the potential role of neuroimmune dysfunction in depressive disorders. The etiology of winter depression (seasonal affective disorder, or SAD) is not known, but a number of studies have provided support for both photoperiod and neurotransmitter hypotheses.


OBJECTIVE
A new hypothesis is presented that links the SAD data on melatonin, photoperiod, and neurotransmitters by proposing that seasonal increases in proinflammatory cytokines are critical in the pathophysiology of winter SAD.


METHODS
In SAD patients, but not healthy subjects: proinflammatory cytokines will be increased and the Th1/Th2 balance will be shifted to the left in winter compared to summer; neuroimmune function will be correlated with nocturnal melatonin duration in SAD patients; and light treatment will correct neuroimmune dysfunction.


CONCLUSIONS
Diagnostic tests for SAD may be developed using cytokine assays; neuroimmune dysfunction may be predictors of response to treatments; new treatments for SAD (immune or anti-inflammatory treatment) may be developed.
Lam
Raymond W
RW
Division of Clinical Neuroscience, Department of Psychiatry, University of British Columbia (UBC), 2255 Wesbrook Mall, Vancouver, BC, Canada V6T 2A1. r.lam@ubc.ca
Song
Cai
C
Yatham
Lakshmi N
LN
D000818:Animals; D006801:Humans; D008550:Melatonin / Q000276:immunology*; D008954:Models, Biological; D020078:Neurogenic Inflammation / Q000150:complications / Q000276:immunology*; D015213:Neuroimmunomodulation / Q000276:immunology*; D017440:Photoperiod; D016574:Seasonal Affective Disorder / Q000150:complications / Q000276:immunology*; D012621:Seasons; D013223:Statistics as Topic
D008550:Melatonin