Recent systematic review s have shown that  light therapy  is an efficacious and well-tolerated treatment for SAD .
There is also evidence for efficacy of pharmacotherapy to treat and prevent SAD .
SAD is a common condition with significant psychosocial impairment .
BACKGROUND Seasonal affective disorder ( SAD ) consists of recurrent major depressive episodes in the fall/winter with remissions in spring/summer .
RESULTS A careful history is important to make the diagnosis and differentiate SAD from other similar conditions such as subsyndromal SAD and atypical depression .
Seasonal patterns with winter worsening are also recognized in " nonseasonal " depression as well as many other psychiatric conditions , and comorbidity with SAD is common .
The pathophysiology of SAD seems to be heterogeneous as research on circadian , neurotransmitter function and genetic hypotheses have shown discrepant results .
A dual vulnerability model with differential loading on separate seasonal and depression factors has been proposed to explain these findings .
Mood and energy regulation in seasonal and non-seasonal depression before and after midday treatment with physical exercise or bright light
The effects of two non-drug treatments ( physical exercise and bright light ) on mood , body weight and oxygen consumption were compared in age-matched groups of female subjects with winter depression , non-seasonal depression or without depression . It was found that oxygen consumption in the pre-treatment condition was similar in non-depressed subjects ( n=18 ) and depressed non-seasonals ( n=18 ) , while comparatively lower values were obtained in winter depression ( n=27 ) . Neither mood nor metabolic parameters changed significantly in the group of nine untreated winter depressives . One week of physical exercise ( 1-h pedaling on a bicycle ergometer between 13.00 and 14.00 h ) increased oxygen consumption in the group of nine winter depressives and lowered oxygen consumption in nine-subject groups of depressed and non-depressed non-seasonals . One week of bright light treatment ( 2-h exposure to 2500 lux between 14.00 and 16.00 h ) increased oxygen consumption in nine winter depressives and nine non-depressed subjects , while no significant change in oxygen consumption was found in nine subjects with non-seasonal depression . Weight loss was observed in the groups treated with physical exercise and in the group of light-treated winter depressives . Winter depression responded equally well to exercising and light , while a significant therapeutic difference in favor of exercising was found in non-seasonal depression . Overall , the results of the study suggest that energy-regulating systems are implicated in the antidepressant action of the non-drug treatments
Recent systematic review s have shown that  light therapy  is an efficacious and well-tolerated treatment for SAD .
There is also evidence for efficacy of pharmacotherapy to treat and prevent SAD .
SAD is a common condition with significant psychosocial impairment .
BACKGROUND Seasonal affective disorder ( SAD ) consists of recurrent major depressive episodes in the fall/winter with remissions in spring/summer .
RESULTS A careful history is important to make the diagnosis and differentiate SAD from other similar conditions such as subsyndromal SAD and atypical depression .
Seasonal patterns with winter worsening are also recognized in " nonseasonal " depression as well as many other psychiatric conditions , and comorbidity with SAD is common .
The pathophysiology of SAD seems to be heterogeneous as research on circadian , neurotransmitter function and genetic hypotheses have shown discrepant results .
A dual vulnerability model with differential loading on separate seasonal and depression factors has been proposed to explain these findings .