Seasonal affective disorder (SAD), also known as seasonal depression, is a type of depression caused by long, gloomy winter days. SAD begins and finishes at roughly the same period each year. If you’re like most SAD sufferers, your symptoms begin in the fall and last into the winter, draining your energy and making you cranky. These symptoms usually go away in the spring and summer.

SAD induces depression less frequently in the spring or early summer and resolves in the fall or winter. Symptoms specific to winter-onset SAD, sometimes called winter depression, may include oversleeping, appetite changes, especially a craving for foods high in carbohydrates, weight gain, tiredness, or low energy.

Causes

Seasonal affective disorder’s exact cause is unclear. Some of the things that may come into play are as follows:

Your biological timer (circadian rhythm). Winter-onset SAD may be caused by the decreasing amount of sunlight in the fall and winter. This lack of sunshine may cause your body’s internal clock to malfunction, leading to depression.

Serotonin levels are high. SAD may be caused by a decrease in serotonin, a brain chemical (neurotransmitter) that modulates mood. Reduced sunshine can induce a decrease in serotonin, which can lead to depression.

Melatonin levels are low. The change in season can upset the body’s melatonin balance, which influences sleep patterns and mood.

When to see a doctor?

It’s common to have low days from time to time. However, if you’re feeling depressed for days at a time and can’t get inspired to do things you generally love, consult your doctor. This is especially crucial if your sleeping and eating habits have changed, you use other medicines for comfort or relaxation, you feel hopeless, or you consider suicide.