Support for Seasonal Affective Disorder

Support for Seasonal Affective Disorder

Cyrus Kuhzarani R.Phm.

07 Oct 2021

Support for Seasonal Affective Disorder

The majority of North Americans are deficient in Vitamin D especially when especially in the winter.  Vitamin D induces the expression of Tryptophan hydroxylase which is the rate limiting enzyme involved in the production of serotonin.1 (see Figure 1)


Figure 1


Light therapy has been found to improve the production of Vitamin D which indirectly improves the production of serotonin helping to improve mood and well-being.3
Limited sun exposure has been associated with symptoms of Seasonal Affective Disorder (SAD). 

Individuals with SAD have lower blood levels of Vitamin D, and many doctors have been found to prescribe between 1000 IU and 4000 IU to cope with symptoms of seasonal affective disorder.4 Low serotonin levels will lead to poor melatonin production and other neurotransmitters may be affected as well.5 

Overproduction of melatonin during the dark days of fall and winter can also increase sleepiness.  Both serotonin and melatonin maintain the body’s daily rhythm that is tied to the night/day cycle.  In people with SAD changes in serotonin and melatonin levels disrupt daily rhythms leading to sleep, mood, and behaviour changes.6

In winter, the predominant theory is that there is a misalignment in circadian rhythms which occurs and is responsible for the symptoms of SAD.  Appropriately timed treatments with light, melatonin, or a combination of the two is the most optimal treatment of choice.7
When you aren’t getting enough sun over a long period of time, melatonin manufacturing will occur at suboptimal times during the day, so there must be strategic supplementation.5


B Vitamins are also critical to the production of neurotransmitters.  Research has shown that folic acid is critical for the production of SAM-e, which stimulates other biochemical cycle that are involved in the production of serotonin, dopamine and norepinephrine.8 Vitamin B12 is also involved in the methylation process allowing SAM-e to stimulate the production of neurotransmitters.9 Active forms of the B vitamins may also be critical in some cases, especially in those with MTHFR gene mutations. 


Furthermore, with the production of serotonin Vitamin B6, folate and zinc are all important cofactors that play an important role in generating serotonin (see Figure 2).10


Figure 2


Seasonal affective disorder affects many individuals during the winter months. 

The strategic use of Light Therapy, B Vitamins, Melatonin, and Vitamin D3 can help to mitigate these symptoms. 


Reference List

  1. Sabir, Marya S et al. 2018. “Optimal vitamin D spurs serotonin: 1,25-dihydroxyvitamin D represses serotonin reuptake transport (SERT) and degradation (MAO-A) gene expression in cultured rat serotonergic neuronal cell lines,” Genes and Nutrition 13 no. 19 (July), September 15, 2021).
  1. Hussain, Azher M et al. 2000. Effect of Aging on Tryptophan Hydroxylase in Rat Brain: Implications on Serotonin Level,” Drug Metabolism and Disposition 28 no. 9, (accessed September 20, 2021).
  1. Petric, Dominic, 2018. “Seasonal Affective Disorder and Vitamin D deficiency.” Abstract in Research Gate.


  1. Renew Health and Wellness Blog. September 15, 2021).


  1. Mental Health Daily Blog. (accessed September 16, 2021).


  1. The National Institute of Mental Health: Seasonal Affective Disorder. (accessed September 16, 2021).


  1. Brown, Gregory M et al. 2009. Chapter: The role of Melatonin in Seasonal Affective Disorder. Seasonal Affective Disorder: Practice and Research, 2nd Ed. Timo Partenen et al. Oxford University Press.


  1. Vasquez, Sarah. 2020. 7 Best Supplements for Seasonal Affective Disorder. Woman’s World, February 9. (accessed September 16, 2021).


  1. The Nest Blog. (accessed September 16, 2021).


  1. Sea Coast Online Blog. (accessed September 20, 2021).




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