For many people, the arrival of spring is a relief: the cold is over, the sun is starting to shine again, and we feel more eager to go outside. For about 3 out of every 100 Dutch people, however, this change is even more relevant; for them, it marks the end of their annual recurring depression.
Winter depression is likely strongly influenced by the short winter days, which (at their lowest point) receive up to five times less sunlight than summer days. For people with seasonal affective disorder (SAD), this decrease in sunlight—combined with spending more time indoors and individual vulnerability—leads to symptoms that closely resemble those of a disrupted biological clock. The treatment of choice of these symptoms, such as low mood, fatigue, and sleep problems, is light therapy.
During the dark winter days, light therapy can offer a solution. But what happens if your profession allows you to escape this cloud cover almost daily, resulting in no dark winter days whatsoever? In other words, would pilots, who spend a significant portion of their working hours above the clouds and in direct sunlight, suffer less from winter depression?
This issue turns out to be not so easy to resolve. Yes, on the one hand, pilots are exposed to more direct sunlight in the winter, but on the other hand, this light doesn’t always come at the right time. Pilots flying intercontinental routes experience jet lag due to time differences between departure and arrival locations. In addition, work schedules are often irregular, causing many pilots to be awake at unnatural times and exposed to light. This, too, can disrupt the biological clock. The extent to which the negative effects of these circadian disruptions outweigh the protective effects of increased winter light exposure varies by pilot (and their work schedule). Whether a pilot ultimately develops seasonal affective disorder therefore remains a highly personal matter, with the amount and timing of light exposure, along with individual factors, ultimately being the deciding factors.
A paper on this topic was recently published in Op de Bok 1 2026 B, a journal of the Association of Dutch Airline Pilots.