Winter depression: Shine some light on your dark mood

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Each year, starting when winter approaches, some of us will begin to feel sluggish and gloomy.

If that sounds like you, know what you’re not alone. In fact, winter depression accounts for about 10% of cases of major depression. The Harvard Mental Health Letter took a look at seasonal affective disorder, and explored whether a little bright light can alter this dark mood.

sunlight in winter - SAD

Winter days can be SAD days

Seasonal affective disorder (SAD) is defined as depression that occurs repeatedly at the same time of year, usually starting in the fall and ending in the spring. People with SAD are sad, tired, anxious, irritable, unable to concentrate, and inclined to avoid friends and social activities. But often they have physical symptoms as well — such as overeating and excessive sleep.

People troubled by depression usually experience their dark moods in an on-again, off-again fashion. In that respect, seasonal affective disorder (SAD) differs only in that the oscillations follow a seasonal schedule, with the depression usually starting in the fall and lasting through the spring.

Studies suggest that SAD runs in families. Additionally, seasonal depression is thought to be more common and longer-lasting at high latitudes, so it appears to also stem from changes in the length of the day.

Lack of light and seasonal depression – what’s the link?

Lack of light is often blamed for SAD, but just how darker days cause depression in SAD sufferers is still in question.

Experts debate whether it has been proved that lack of sunlight in winter triggers SAD, but there’s certainly circumstantial evidence to support the connection. How might lack of light cause depression?

Three theories:
  1. The root cause may be insensitivity to light. Most of us go through winter on a relatively even keel because exposure to indoor lighting helps offset the lack of natural light, but indoor light may be too weak for SAD sufferers.
  2. There are neural pathways from the eyes’ retinas to parts of the brain that help put many of our physiological processes on a 24-hour cycle. Lack of light may put people with SAD out of phase with their biological clocks: awake and active when their internal timers want them snug in bed.
  3. A lack of light, or insensitivity to it, may disrupt brain processes influenced by serotonin and dopamine, brain chemicals that play a role in mood.
    Light therapy, which involves sitting in front of a bright light for a short time each day, helps some people who suffer from SAD. But antidepressant medications may work just as well, says the Harvard Health Letter.
Sunlight – or bright light – can help

Sunlight has always been regarded as an antidote to lethargy and gloom. Bright light treatment for SAD involves mounting fluorescent lights on a metal reflector, with a plastic screen that filters out damaging ultraviolet frequencies and diffuses the light to prevent glare. The patient sits near this apparatus for a half-hour to two hours a day. Experts usually recommend 10,000 lux, which is about the equivalent to early morning sunlight. Improvement begins in a few days and treatment continues throughout the winter. There are a few side effects, mainly occasional headaches or eyestrain.

For milder seasonal mood changes, the November issue recommends adding more lamps, sitting near windows, or spending more time outdoors. One study found that an hour’s walk in winter sunlight was as effective as 2-1/2 hours of artificial light. Other treatment approaches include the use of antidepressant drugs and the herb St John’s wort. People with SAD may also benefit from cognitive behavioral therapy.

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