Seasonal depression, or seasonal affective disorder (SAD) is a form of depression that comes and goes according to the season. In most people, winter is the time they experience seasonal depression. In a minority, it’s the summer.
According to the Australian government website Health Direct (see their article ), symptoms of seasonal depression in the winter are:
- lack of energy
- sleeping too much
- finding it hard to wake up in the morning
- feeling very tired all the time
- overeating and craving carbohydrates
- gaining weight
- losing interest in normal activities
Conversely, if you suffer it in the summer, symptoms are more likely to be:
- trouble sleeping
- not feeling hungry
- losing weight
- feeling agitated and anxious
Wikipedia’s article adds that feelings of hopelessness or worthlessness, thoughts of suicide, withdrawal from social interaction, and loss of libido may also be symptoms. Under the DSM-5, SAD is not a distinct condition, but a specifier (called “with seasonal pattern”) for major depressive disorder that recurs consistently at a set time of year and is absent otherwise. Wikipedia also distinguishes between SAD and what it calls Subsyndromal Seasonal Affective Disorder, which is less severe, and about 2.5x as common as “true” SAD.
The cause of SAD is not super clear, but is thought to have something to do with disruption to the circadian rhythm as a result of the changing day length (in the more common wintertime depression variety, it’s thought to do with lack of bright light, especially in the early morning to signal to your body “hey, it’s a brand new day!”). Apparently SAD is more common in people with certain personality traits, namely openness, agreeableness, neuroticism and an avoidance-based coping style.1
The primary treatment for SAD seems to be bright light therapy. The idea is that you buy this special lightbox, and sit in front of it soaking up its very bright light (supposed to mimic the strength of daylight) for at least 30 minutes as early as you can in the morning. Where this treatment works, improvement is observed within a few days. It’s also recommended to try to allow as much external light into your home as you can, and to go outside during the daylight hours, getting in some exercise like a walk. If these “light exposure” type treatments prove inadequate, other measures include vitamin D supplements (if your vitamin D levels are low), antidepressant medication, or counselling.