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 .
Controlled trial of bright light and negative air ions for chronic depression.
BACKGROUND This r and omized controlled trial investigates the efficacy of two non-pharmacologic treatments , bright light and high-density negative air ions for non-seasonal chronic depression .  Both methods have shown clinical success for seasonal affective disorder ( SAD ) . METHOD Patients were 24 ( 75 % ) women and 8 ( 25 % ) men , ages 22 - 65 years ( mean age + /- S.D. , 43.7 + /- 12.4 years ) , with Major Depressive Disorder , Single Episode ( DSM-IV code , 296.2 ) , Chronic ( episode duration > or = 2 years ) . Patients were entered throughout the year and r and omly assigned to exposure to bright light ( 10 000 lux , n = 10 ) , or high-density ( 4.5 x 10(14 ) ions/s flow rate , n = 12 ) or low-density ( 1.7 x 10(11 ) ions/s , n = 10 , placebo control ) negative air ions . Home treatment sessions occurred for 1 h upon awakening for 5 weeks . Blinded raters assessed symptom severity weekly with the Structured Interview Guide for the Hamilton Depression Rating Scale -- Seasonal Affective Disorder ( SIGH-SAD ) version . Evening saliva sample s were obtained before and after treatment for ascertainment of circadian melatonin rhythm phase . RESULTS SIGH-SAD score improvement was 53.7 % for bright light and 51.1 % for high-density ions v. 17.0 % for low-density ions . Remission rates were 50 % , 50 % and 0 % respectively . The presence or severity of atypical symptoms did not predict response to either treatment modality , nor were phase advances to light associated with positive response . CONCLUSIONS Both bright light and negative air ions are effective for treatment of chronic depression . Remission rates are similar to those for SAD , but without a seasonal dependency or apparent mediation by circadian rhythm phase shifts . Combination treatment with antidepressant drugs may further enhance clinical response
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 .