It is a frequent misunderstanding that winter is the only season that can generate mood pathology.

Anyone who has endured a long, cold winter has probably encountered a touch of the “winter blues.” This is a fairly normal experience whereby we might become lethargic, carb-craving and a little moody. It tends not to be what psychology professionals term “pervasive,” meaning it doesn’t significantly affect our ability to function. It is also important to note that the popular term “Seasonal Affective Disorder” is not an official diagnosis. This is more of a pop cultural term for seasonally-occurring depression, though sometimes adopted by professionals, too.

Have no doubt, however! Seasonal mood changes are indeed specifiers within MDD and Bipolar spectrum illnesses, e.g., MDD with Seasonal Onset. Note that the specifier is with Seasonal Onset, not specifically winter onset. Interestingly, there is a subset of people with Seasonal Onset who become depressed in the brighter months. Individuals with Bipolar Disorders can also become hy/manic with the seasons. Today we focus on Major Depression with Seasonal Onset.

The most common manifestation of Seasonal Onset is indeed MDD correlated with shortening days. This presentation is up to four times more prevalent in females and increases the further people live from the equator (Melrose, 2015). A popular theory is that it stems from lack of vitamin D, which sunlight naturally provides, and is well-known to be correlated with healthy moods. It seems that a big role of vitamin D is regulating serotonin transporters, particularly one called “sert.” People prone to Seasonal Onset moods seem prone to vitamin D sensitivities, most likely a genetic nuance (Stewart et al., 2014). Patients who have a pattern of developing an MDD episode as the days shorten seem to have an overabundance of sert (Ruhe et al., 2011; McMahon, 2016). Thought of another way, there is not enough vitamin D to act as a bouncer, allowing in only the right percentage of sert to the party. With too much sert on the scene, serotonin is then just being ushered through, not being allowed to have much of an effect on mood regulation. It is no secret that minimal serotonin saturation is highly correlated with depression.

Conversely, it stands to reasons that the rare individuals who develop MDD in correlation to increasing sunlight may have too much sert regulation. Their bouncer is stingy and won’t admit enough to the party. The brain is again not being saturated with serotonin, but now it is because there aren’t enough escorts to deliver all that is needed. In exceptionally rare cases, MDD episodes develop during both seasonal shifts.

The Presentation:

Of note, Seasonal Onset MDD seems correlated to an Atypical Features presentation (Harvard, 2014). What is most noteworthy, though, is when it makes its appearance. First, however, it is important to realize that the seasonal shifts aren’t the only time patients with Seasonal Onset may get depressed; they could have a general ebbing and flowing of episodes. However, like clockwork, each year as the sunlight changes, they indeed settle into a depressive episode..

Diagnostic criteria notes that the seasonal pattern must be established as at least two consecutive instances of seasonal onset with full remission as the season changes. There is no seasonal demarcation indicating what’s too little or too much sunlight, meaning it doesn’t simply happen at the extremes, closest to solstices. Autumn’s case helps illustrate:

Autumn, a 30-year-old professional, met with Dr. H after noticing a significant downward spiral as the fall progressed. She reported that, for several years she felt “blue” off and on in the winter, but if she took occasional trips down South to see her parents, and kept busy, she muddled through it and was good until the next winter. This time, the “blue” feeling started in September, and she slowly found herself overeating and fatigued on top of the blueness, which was quickly turning to gray as she headed into November. “As the day wears on at work I feel a brain fog and all I want to do is get home after work and hunker down to a movie, but I usually fall asleep halfway though,” she described. “The other day at work I was moving all slow, and my colleague told me I didn’t look good. If other people are seeing it, I figured I better call someone!” Autmn finished.

Autumn’s experience is not unusual. If we ask Seasonal Onset patients to think about when first symptoms bubbled up, we may see the Seasonal Onset was a months-long, insidious process until they met MDD criteria. Depending on the person’s sensitivity, their mood could begin changing in the late summer as days are noticeably shortening. I’ve met others who don’t get depressed until we only have 10 hours or less of sunlight. Untreated symptoms may remit as soon as days begin lengthening, or take well into spring.

Treatment Implications:

I’ve told patients with Seasonal Onset, that in a way, it’s the best kind of MDD to get, because you know what to expect and can prepare for it. This is especially true if it is the only time they experience depression. Patients who struggle with depression throughout the year should be doing much of what follows already, but we may need to help them increase the activity if they are prone to Seasonal Onset. In therapy, we can reflect on the impending seasonal pattern, and help them assemble their survival kits:

  • Many choose to discontinue their antidepressant after the seasonal depression ends. If so, arranging a visit with their psychiatrist at least a month prior to the normal onset of depression symptoms is essential. This will allow the medication time to take effect ahead of the curve.
  • Vitamin D lamps have been met with some success by many. Encourage patients to discuss this with their psychiatrist.
  • It is no secret that exercise has a big effect on mood. If they aren’t exercisers in general, develop a physical activity plan (after consultation with their physician, of course). If they already do exercise, perhaps increasing the number of days going to the gym, or getting a gym partner to keep them motivated will be necessary.
  • Winter depression is correlated with increased appetite and especially carb cravings, which can add weight and further moodiness from sugar spikes and crashes. Review the importance of the effect of diet on mood, and encourage a visit with a nutritionist to help patients maximize a diet conducive to bettering mood. Diets high in Vitamins E and D, folate, and lean protein are well-researched as “medical foods” for fighting depression, especially in conjunction with antidepressant medications.
  • Finding increased structure at a time of year that even non-depressed people tend to hibernate. This could be engaging in volunteer work, making it more of a point to engage in hobbies, or arranging regular social outings. Clients have found it helpful, for example, to be held to having coffee each day after work with a different family member or friend, and lunch every Sunday with their siblings at a different restaurant.

All along, the good therapist will be a supportive task master for the above, along with helping their patients manage the inherent day-to-day struggles. This may be cognitive-behavioral approaches to improving motivation, managing relationships that could become wrinkled due to their depressed state (especially sexual, given libido can decline with depression and be further reduced by some antidepressants), and managing the low self-esteem and dark thoughts that ebb and flow with depressed states.

Remember, the needs of each patient are different, so it’s important to review progress and what they feel they require. Not everyone needs weekly therapy during seasonal depression. Thankfully, many do well with medication, diet and exercise and only require a seasonal check-in to prepare.


Harvard (2014, December). Seasonal affective disorder. Harvard Health Online. Retrieved from

McMahon B, Andersen SB, Madsen MK, et al. Seasonal difference in brain serotonin transporter binding predicts symptom severity in patients with seasonal affective disorder. Brain. 2016;139(Pt 5):1605-1614. doi:10.1093/brain/aww043

Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches.Depression research and treatment,2015, 178564.

Ruh, H.G., Booij, J., Reitsma, al.Serotonin transporter binding with [123I]?-CIT SPECT in major depressive disorder versus controls: effect of season and gender.Eur J Nucl Med Mol Imaging36,841849 (2009).

Stewart AE, Roecklein KA, Tanner S, Kimlin MG. Possible contributions of skin pigmentation and vitamin D in a polyfactorial model of seasonal affective disorder.Med Hypotheses. 2014;83(5):517-525. doi:10.1016/j.mehy.2014.09.010