No one is thrilled to see summer end, but for some of my patients, the shortening daylight and grayer weather of fall and winter bring on something more than a seasonal mood dip. It’s a real mood disorder, and it has a name: seasonal affective disorder, or SAD.
SAD is also known as winter depression or the winter blues — a pattern where people who are otherwise mentally healthy begin experiencing depressive symptoms as fall and winter arrive. A summer version exists too, though it’s far less common in my experience.
What triggers it
Reduced daylight during the fall and winter months appears to be the central trigger in people who are susceptible, with genetics, age, and individual differences in brain chemistry all playing a role. The brain produces melatonin during periods of darkness, which helps regulate sleep, body temperature, and hormone release. In people with SAD, that melatonin production increases beyond what’s useful, disrupting the internal body clock and contributing to depressive symptoms. If depressive episodes reliably start in fall or winter and lift again in spring or summer, SAD is worth considering.
Recognizing the symptoms
- Depressed mood, irritability, or a sense of hopelessness
- Anxiety and loss of energy
- Social withdrawal and oversleeping
- Diminished interest in activities that are normally enjoyable
- Carbohydrate cravings and weight gain
- Difficulty concentrating
Light therapy
Light therapy works by using exposure to bright light as a way of sending new signals to the brain and lifting depression. A 10,000-lux light box requires about 30 minutes of daily exposure; a 5,000-lux box needs roughly 60 minutes. Patients typically sit 12 to 18 inches away with their eyes open, though there’s no need to stare directly at the light. I generally recommend morning use, since using it later in the day can interfere with sleep. Anyone with bipolar disorder or a history of manic episodes should only use light therapy under medical supervision, since it can trigger a manic episode.
Medication and other approaches
Antidepressant medication is effective for SAD as well, and it’s sometimes combined with light therapy for a stronger response. Correcting low vitamin D levels has also shown benefit for some patients. Beyond these, counseling that helps someone recognize the early signs of a seasonal episode and manage the negative thinking that comes with it, stress management, nutrition-focused support, social skills work, and simply identifying enjoyable winter activities can all make a meaningful difference. Sleep management is also worth addressing directly, since oversleeping and disrupted sleep patterns are so often part of the picture.
What I find reassuring to tell patients is that SAD is one of the more predictable mood conditions I treat — because the pattern repeats on a calendar, we can often start light therapy proactively each fall rather than waiting for a full episode to develop.
Seasonal affective disorder is genuinely treatable, and for most patients the combination of light therapy, and sometimes medication, makes a real difference well before winter is over. If this pattern sounds familiar, it’s worth talking through before the season turns again.