At the winter solstice, Minneapolis gets eight hours and forty-six minutes of daylight, and much of it is overcast. The clinical consequences are well documented and routinely self-managed with mixed information.

Seasonal affective disorder is a recognized pattern of major depression with seasonal onset, and prevalence rises with latitude. Estimates for Minnesota place it in the range of five to ten percent of adults, with a larger share experiencing milder seasonal mood changes that fall short of a diagnosis.

Light therapy is the best-supported first-line treatment. The evidence favors a 10,000-lux light box used for twenty to thirty minutes within an hour of waking, positioned at an angle rather than stared into. Efficacy in trials is comparable to antidepressant medication for seasonal patterns.

Timing matters more than most users realize. Evening use can delay circadian rhythm and worsen sleep, and clinicians report that incorrect timing is the most common reason a patient concludes the device does not work.

Vitamin D is the most discussed and least clearly supported intervention. Deficiency is genuinely widespread at this latitude in winter, and supplementation corrects it. Whether correcting it improves mood is not well established; trials have been largely disappointing.

Clinicians tend to recommend it anyway, for bone health, while being careful not to promise mood effects.

Exercise has better evidence than supplements and worse compliance. Outdoor exercise appears to help more than indoor, plausibly because of light exposure, which is also the hardest recommendation to follow in February.

Sleep timing is the intervention clinicians describe as most underused. Holding a consistent wake time through the winter, even on weekends, stabilizes circadian rhythm more effectively than most interventions patients try first.

What clinicians uniformly discourage is waiting. Seasonal patterns are predictable, which means they are preventable, and starting light therapy in October works better than starting it in January.

"Everyone comes in February," a psychiatrist at a Minneapolis clinic said. "By February you have had ten weeks of it. We would much rather see you in the fall, when you feel fine and know what is coming."