Seasonal affective disorder or hormones? A men’s guide to winter mood, testosterone, and sleep

In men, winter “low mood” can be true seasonal affective disorder (a recurrent depressive pattern that starts in late fall, peaks in winter, and eases as daylight returns) or a look‑alike driven by physiology—less morning light can delay your circadian rhythm and prolong melatonin, while testosterone, cortisol, and thyroid shifts can produce the same fatigue and low drive. Here’s how to tell which is more likely, what to test, and what actually helps you feel normal again.

By Men’s Health Editors

The relationship

Seasonal affective disorder is a subtype of depression with a predictable pattern: symptoms show up in late fall, peak in winter, and ease as daylight returns.^[1] In men, it often looks less like sadness and more like low drive, irritability, heavier sleep, and “why bother” energy at work and in the gym.

Here’s the twist: the same winter inputs that can trigger SAD also nudge the hormone systems that regulate mood and recovery. Less morning light can shift your circadian rhythm, meaning your internal clock drifts later, and your melatonin window can stretch longer. Melatonin is a hormone that helps signal “night” to your brain. If it runs long, you can feel groggy, unmotivated, and socially withdrawn even when you get enough hours of sleep.

At the same time, low mood and fatigue can be driven by hormone imbalance that has nothing to do with seasonality. Testosterone, cortisol, and thyroid hormones affect serotonin, dopamine, sleep quality, and metabolism. Serotonin is a brain chemical tied to mood stability. Dopamine is a brain chemical tied to motivation and reward. In other words, “seasonal affective disorder hormones” is not a gimmick phrase. It reflects real overlap in biology that can confuse the diagnosis.

How it works

Light, circadian rhythm, and melatonin

Circadian rhythm is your 24-hour body clock that times sleep, alertness, and hormone release. Short winter days can delay circadian timing in vulnerable people, and that mismatch between your schedule and your internal clock is one proposed driver of seasonal depression. Melatonin is a hormone released at night; in winter, the melatonin signal can extend, which can increase sleepiness and make mornings feel brutal.

For men, this often shows up as “I can’t wake up” plus “I don’t feel like myself until noon,” followed by late-night alertness that pushes bedtime later. That pattern matters because testosterone is normally highest in the morning, and chronic sleep disruption is linked with lower testosterone production over time.^[5]

Serotonin, dopamine, and the “winter chemistry” shift

Season and sunlight exposure are associated with changes in serotonin activity in the brain, and lower light is linked with lower serotonin turnover.^[2] That matters because serotonin supports mood steadiness, and dopamine supports motivation, goal pursuit, and the “this feels rewarding” signal.

This is why seasonal affective disorder can feel like more than sadness. Many men describe it as emotional numbness, carb cravings, and a preference to isolate. If you already have high stress or poor sleep, the light-driven changes can stack on top of an already strained system and push you into a true depressive episode.^[1]

Testosterone and estradiol: mood, drive, and resilience

Testosterone is the primary male sex hormone, and it influences mood and motivation partly through interactions with serotonin and dopamine pathways.^[6] Estradiol is a form of estrogen that men make by converting some testosterone; in normal ranges, it supports bone, brain, and sexual function, but extremes can be associated with symptoms that overlap with depression and fatigue.

Clinically, low testosterone can look like winter depression: low energy, low libido, reduced morning erections, lower training tolerance, and a shorter fuse. It can also worsen sleep, which then worsens mood, creating a loop. If seasonal affective disorder hormones are part of your story, this is the point where lab work stops guesswork.

Diagnostic thresholds used in practice: meta-analyses indicate that symptomatic men with total testosterone below 350 ng/dL, about 12 nmol/L, are most likely to benefit from TRT. If total testosterone is borderline, measure free testosterone. Free testosterone is the unbound, biologically active fraction. Values below 100 pg/mL, about 10 ng/dL, support hypogonadism when symptoms persist.^[5]

Cortisol and thyroid hormones: stress, metabolism, and energy

Cortisol is the main stress hormone made by the adrenal glands. Depression is associated with altered activity of the HPA axis, the hypothalamic-pituitary-adrenal system that controls cortisol release, and research over decades shows measurable differences in cortisol patterns in many people with depression.^[7] In men, high chronic stress can present as early waking, anxiety, abdominal weight gain, and “wired but tired” fatigue that gets mislabeled as purely seasonal.

Thyroid hormones regulate metabolic rate and energy. Thyroid dysfunction can mimic depression with fatigue, low motivation, cold intolerance, and brain fog, and thyroid measures show seasonal variation in some populations.^[8] The practical point: if you’re chasing “winter blues” with supplements and grit, but your thyroid or stress biology is off, you’re treating the wrong target.

Conditions linked to it

Because seasonal affective disorder and hormones overlap, clinicians often look for common “look-alikes” and add-ons. In men, these are some of the most relevant conditions to consider:

• Major depressive disorder with seasonal pattern. SAD can be a seasonal pattern of depression rather than a separate problem, and it can require the same seriousness in assessment and treatment.^[1]
• Testosterone deficiency. Also called hypogonadism, meaning the testes are not producing enough testosterone for normal function. Symptoms can overlap heavily with SAD, including low mood and fatigue.^[5]
• Sleep disorders. Circadian delay, insomnia, and obstructive sleep apnea can worsen winter fatigue and lower mood. If you snore, wake up choking, or feel unrefreshed, treat sleep like a core cause, not a side note.
• Thyroid dysfunction. Underactive thyroid can present as depression-like symptoms and low energy, and thyroid markers can vary by season.^[8]
• High chronic stress and burnout. HPA axis changes can overlap with depressive symptoms and sleep disruption.^[7]

Limitations: Hormones and mood interact in both directions. Depression can worsen sleep and activity, which can lower testosterone and change cortisol patterns. So a single lab result rarely “explains everything.” The goal is pattern recognition: symptoms, seasonality, sleep timing, and repeat morning labs interpreted together.^[5]

Symptoms and signals

If you’re trying to figure out whether seasonal affective disorder hormones are driving your winter slump, watch for clusters, not single symptoms.

• Seasonal timing: symptoms start around late fall, peak in winter, and ease in spring most years.^[1]
• Sleep changes: longer sleep, hard mornings, daytime sleepiness, or a bedtime that drifts later.
• Energy and training signals: workouts feel harder, recovery is slower, and your usual routine feels “too much.”
• Mood and behavior: irritability, low motivation, social withdrawal, lower confidence, or feeling emotionally flat.
• Appetite shifts: carb cravings and slow weight gain during winter months.
• Sexual function signals that point to hormones: lower libido, fewer morning erections, erectile dysfunction, reduced intensity of orgasm, or reduced ejaculate volume.
• Red flags: thoughts of self-harm, hopelessness, or inability to function at work or home. Treat this as urgent medical care.

What to do about it

You can treat winter mood as a performance problem with a medical backbone: measure the likely drivers, act on proven tools, and monitor like you would blood pressure or lifting progress.

1. Step 1: test the basics that change the plan.

   Start with a clinician visit focused on mood, sleep, and sexual function. Ask for morning labs, ideally drawn early and repeated if borderline. Common first-pass tests in men include total testosterone, free testosterone if needed, SHBG, LH, FSH, and prolactin for the testosterone axis, plus TSH for thyroid screening and basic labs to rule out anemia or systemic illness. Follow guideline-based evaluation before considering TRT.^[5]

   If symptoms are clearly seasonal, also screen for depression severity and suicidality. Seasonal pattern does not make depression “minor.”^[1]

2. Step 2: use proven winter interventions, then add hormone treatment only when indicated.

   Bright light therapy is one of the best-studied treatments for SAD. Meta-analyses show it can reduce depressive symptoms, especially when used consistently in the morning.^[3] A common clinical protocol is a 10,000-lux light box shortly after waking, used daily during the season, with timing personalized to your sleep pattern.

   Cognitive behavioral therapy for SAD is another evidence-based option that can be as effective as light therapy for many people and may help reduce relapse across winters by changing habits and winter-specific thinking loops.^[4]

   Medication can be appropriate, especially if symptoms are moderate to severe. Evidence supports antidepressant approaches for SAD, including prevention in people with a clear annual pattern, with bupropion XL commonly studied for prevention.^[9]

   Hormone treatment is not a first-line “winter mood hack.” But if you have consistent symptoms plus low testosterone by guideline-based criteria, TRT may improve depressive symptoms in some men, particularly those with lower baseline levels.^[6] This decision should be individualized, with fertility goals, hematocrit, prostate risk, and sleep apnea risk considered.

   Do the unsexy sleep moves. Keep wake time stable, get outdoor light early if possible, train most days, and keep alcohol and late-night screens from becoming the winter coping strategy. These behaviors directly support circadian timing and the hormone signals that follow it.

3. Step 3: monitor and adjust for 6 to 12 weeks.

   Track sleep timing, mood, training consistency, libido, and energy weekly. If you start light therapy, give it daily consistency before judging it. If you begin antidepressant medication or TRT, follow up for symptom response and side effects, and repeat labs as recommended. The goal is not just “feeling better.” It is stable sleep, stable mood, and stable functioning through the darkest months.^[5]

Myth vs Fact

• Myth: “If I’m down in winter, it’s definitely SAD.” Fact: Low testosterone, thyroid dysfunction, sleep apnea, and chronic stress can mimic SAD symptoms in men.^[5],[8]
• Myth: “Light therapy is basically placebo.” Fact: Meta-analyses support bright light therapy as an effective treatment for seasonal depressive symptoms when used correctly and consistently.^[3]
• Myth: “TRT is a mood treatment for any tired guy.” Fact: TRT is most likely to help men with symptoms plus low testosterone confirmed on proper testing. It is not a substitute for treating depression or sleep problems.^[5],[6]
• Myth: “If it’s seasonal, I should just wait for spring.” Fact: SAD is a depression subtype and can be treated now with light therapy, CBT-SAD, and medication when appropriate.^[3],[4]

Bottom line

Seasonal affective disorder and hormones can produce the same winter crash in men: low energy, poor sleep, irritability, and low drive. The smartest approach is dual-track: treat the seasonal trigger with morning light, structured sleep, and evidence-based therapy, while also checking testosterone, thyroid, and stress biology when symptoms persist or include sexual and performance changes.

References

1. Melrose S. Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression research and treatment. 2015;2015:178564. PMID: 26688752
2. Lambert GW, Reid C, Kaye DM, et al. Effect of sunlight and season on serotonin turnover in the brain. Lancet (London, England). 2002;360:1840-2. PMID: 12480364
3. Golden RN, Gaynes BN, Ekstrom RD, et al. The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence. The American journal of psychiatry. 2005;162:656-62. PMID: 15800134
4. Rohan KJ, Mahon JN, Evans M, et al. Randomized Trial of Cognitive-Behavioral Therapy Versus Light Therapy for Seasonal Affective Disorder: Acute Outcomes. The American journal of psychiatry. 2015;172:862-9. PMID: 25859764
5. Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. The Journal of urology. 2018;200:423-432. PMID: 29601923
6. Walther A, Breidenstein J, Miller R. Association of Testosterone Treatment With Alleviation of Depressive Symptoms in Men: A Systematic Review and Meta-analysis. JAMA psychiatry. 2019;76:31-40. PMID: 30427999
7. Stetler C, Miller GE. Depression and hypothalamic-pituitary-adrenal activation: a quantitative summary of four decades of research. Psychosomatic medicine. 2011;73:114-26. PMID: 21257974
8. Ittermann T, Völzke H, Baumeister SE, et al. Diagnosed thyroid disorders are associated with depression and anxiety. Social psychiatry and psychiatric epidemiology. 2015;50:1417-25. PMID: 25777685
9. Gartlehner G, Nussbaumer-Streit B, Gaynes BN, et al. Second-generation antidepressants for preventing seasonal affective disorder in adults. The Cochrane database of systematic reviews. 2019;3:CD011268. PMID: 30883669