Seasonal Affective Disorder (SAD) was first acknowledged in the mid-1980s and affects between 2% and 10% of Americans every year.
Nearly three-fourths of those affected by SAD are women
SAD is thought to be caused by problematic circadian rhythms and imbalances in hormones and neurotransmitters, including serotonin and melatonin, and can result in annually persistent and potentially debilitating symptoms
Symptoms of SAD
Hypersomnia
Fatigue
Increase appetite and weight gain
Difficulty waking in the morning
Feeling depressed or sad much of the day
Loss of interest
Sluggishness
Feelings of hopeless/worthlessness
Circadian Rhythms
The body has a master circadian clock that resides in the suprachiasmatic nucleus (SCM)within the hypothalamus and coordinates rhythms throughout the brain and other systems of the body. The SCM is stays in tune with what’s happening outside the body by tracking light cues through the retina. So circadian rhythms are generated by feedback loops that cycle every 24 hours maintaining the balance of hormones and systems in the body.
The brain uses 20% of the energy for the entire body, so it needs to do so in an efficient manner. And circadian rhythms in the brain are incredibly important for maximizing energy efficiency and health of the neurons. When we’re awake, neurons are constantly firing in response to stimuli. And all of that activity creates the buildup of something called reactive oxygen species (ROS) and other by-products. And during sleep, antioxidants remove excess ROS and other byproducts. Disruptions to the timing and duration of sleep and wake will disrupt these processes. In fact, a recent study found that even one night of sleep deprivation can result in an accumulation amyloid-beta (one of the proteins that accumulates in the brain in Alzheimer’s disease). So, efficient brain function depends on consistent sleep-wake timing.
Patients suffering from SAD often present with a phase-delayed circadian system, meaning that they fall asleep too late in the evening and awaken too early. This alters the body's natural rhythm of hormone secretion affecting mood and energy levels. If patients with winter depression have phase delayed circadian rhythms then adjusting the sleep phase should help regulate the circadian rhythm and improve mood and brain function.
Treatment
Light Therapy: One to two hours of 10,000 LUX light every morning may cause a corrective phase advance. However, it is important to speak with a specialist who can help you understand the best timing and intensity of light therapy. Side effects include mild visual complaints, nausea, dizziness, headaches, tired eyes, agitation, sleep disturbance, and sometimes hypomania.
Melatonin: Research has shown mixed results for the effectiveness of melatonin in helping to correct imbalances in circadian rythm
Bupropion (i.e., Wellbutrin XR): Research has suggested that Bupropion may help relieve the symptoms of SAD in some patients
Supplements such as St. John's Wort, Kava, Ginko Biloba, and Tryptophan have not been extensively studied for treatment of SAD, though some individuals have reported positive results for the treatment of SAD.
Ketchesin, K. D., Becker‐Krail, D., & Mcclung, C. A. (2018). Mood‐related central and peripheral clocks. European Journal of Neuroscience, 51(1), 326-345. doi:10.1111/ejn.14253
Øverland, S., Woicik, W., Sikora, L., Whittaker, K., Heli, H., Skjelkvåle, F. S., . . . Colman, I. (2019). Seasonality and symptoms of depression: A systematic review of the literature. Epidemiology and Psychiatric Sciences, 29. doi:10.1017/s2045796019000209
Zghoul, T. (2020). Can we prevent seasonal affective disorder (SAD) with melatonergic agents? BJPsych Advances, 26(4), 193-197. doi:10.1192/bja.2020.25