With daylight still short in mid-January, the organization that runs Markham Stouffville Hospital is reminding residents that winter can bring on more than a passing slump.

In an article published Jan. 16, Oak Valley Health said its Mental Health Services Program often sees seasonal affective disorder, or SAD, in the colder months, usually from November through March. SAD is a form of depression tied to seasonal change, and the hospital stressed that it is a recognized, treatable condition, not a personal failing.

Why Canadians are vulnerable

The hospital points to geography. In winter, many parts of Canada get fewer than eight hours of daylight a day. Less sunlight disrupts the body's internal clock, which regulates sleep, mood and hormones. It can also lower serotonin, a brain chemical linked to mood, and raise melatonin, which controls sleep, leaving people tired and sluggish.

Research suggests SAD affects 2 to 3 per cent of Canadians, with rates rising farther north, the hospital said. It is diagnosed more often in women, in young adults in their 20s and 30s, in people with a family history of depression or SAD, and in people with limited access to natural daylight, such as shift workers. Anyone can be affected, however.

Symptoms to watch for

SAD is more intense and persistent than ordinary winter fatigue. Signs listed by the hospital include:

  • ongoing low mood or hopelessness

  • loss of interest in activities once enjoyed

  • sleeping too much and having trouble waking

  • a bigger appetite, especially cravings for carbohydrates, and weight gain

  • trouble concentrating

  • pulling away from friends and family

In severe cases, the condition can interfere with work and relationships, and some people may experience anxiety or thoughts of self-harm. Anyone in immediate danger should call 911 or go to the nearest emergency department; the national suicide crisis helpline can be reached by calling or texting 988.

How it is treated

One of the most effective treatments is also one of the simplest: light therapy, which involves sitting near a light box that mimics natural sunlight, typically for 20 to 30 minutes each morning. Many people see their mood and energy improve within weeks, the hospital said.

A SAD light is often prescribed and covered by insurance plans. Because many products claim to treat SAD, the hospital advises speaking to a primary care provider to make sure you get an appropriate one.

Lifestyle changes help too. The hospital recommends regular exercise, time outdoors even on cloudy days, a consistent sleep schedule and staying socially connected to counter winter's isolating effects.