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The days are getting shorter. Daylight savings time ended at 2 a.m. Sunday. Falling leaves will soon be replaced by falling snow.

And for many Canadians, Seasonal Affective Disorder (SAD) will set in. Four to five per cent of Canadians experience severe winter depression, and another 10 to 15 per cent develop a milder form.

Dr. Robert Levitan, a professor in the departments of psychiatry and physiology and the new Cameron Wilson Chair in Depression Studies at the Faculty of Medicine, researches the mechanisms of SAD and how obesity and overeating contribute to the condition. He is also working with the department of obstetrics and gynaecology to explore whether women with SAD have a different pattern of pregnancy than other women.

Levitan, who is also a clinician-scientist at the Centre for Addiction and Mental Health, recently spoke with Faculty of Medicine writer Erin Howe about SAD, and what we can do to protect ourselves from it.

What is Seasonal Affective Disorder (SAD) and how does it differ from depression and the ‘winter blues’?
Clinically, SAD is different from most other depressions in terms of its symptoms, which are highly reminiscent of hibernation. People will sleep much more than usual, eat more than usual, gain weight and withdraw socially. There are many academics in my field, including me, who consider SAD to be an evolutionary disorder, an energy-conserving process that is no longer helpful in modern society. While in modern times it’s not good for us to slow down too much in the winter, or to gain lots of weight, this probably helped our ancestors survive in the ice age.

Are there other ways SAD differs from depression?
The time frame is what defines it.  The fact that SAD has a predictable onset and a predictable offset is unique. It starts around now and it goes away when the clocks change in the other direction. It’s also very prominent among women. About 80 per cent of people with SAD are female. With other forms of depression, about 60 per cent are women.

When is it time to reach out and ask for help?
I think one’s ability to function is a good indicator. If you have difficulty with your normal routine at work or at home, if your relationships are strained because of low energy and you’re irritable, and you really just can’t get through the day at work the way you usually can, this would be a time to get help. Certainly, if there’s any safety issue, because SAD can cause suicidal thoughts for some people. Any of those would be a basis to get assessed, and people can be assessed initially through their family doctor.

In general, with any kind of depression, including seasonal depression, the biggest problem that we have as clinicians is that people don’t ask for the help they need. Some studies suggest as few as one in seven people with depression actually get help.

What treatments might be available to people experiencing SAD?
Light therapy is very effective. Two out of three patients will do well with it. The best predictor of light response is actually carbohydrate craving.

But it’s really important that people don’t use light therapy to self-treat, unsupervised. We’ve had patients use ultra-violet lights, like the ones used for growing plants, for SAD and that’s very dangerous.

Lights must be ultra-violet filtered, and we recommend only commercially-available units that have been tested and are properly filtered. And there are some risks with light therapy; it’s not completely innocuous. Side effects can include headache, eyestrain, and for people with bi-polar disorder, light therapy can induce a bi-polar episode, so that’s a problem as well.

We also use tryptophan quite often, which is an amino acid available in a purified, pill form. It’s a natural way of boosting serotonin and there’s lots of reason to think that serotonin is the main culprit for SAD. We often use tryptophan together with light therapy.

Standard anti-depressants may also be used and research has shown they can be equally as effective as light therapy. For some people, it’s easier to use medication because light therapy is a half-hour time commitment and not always practical, especially for mothers with young children. Having said that, most patients do prefer light as the first line treatment.

When does SAD typically set in?
Some people have recurrent SAD over many years, and they tend to have a pattern where they start to anticipate it early on in the fall as the days get shorter. There’s also a peak around the holidays, going in to January, and it’s always hard to sort out how much of it is related to biological factors versus psychological, social factors. Christmas can be very stressful for people, and falls close to the shortest day of the year, making it a highly vulnerable time. In January and February SAD is at its worst.

Are there things we can do to protect ourselves from SAD?
There are several things that can be quite helpful. Try to maintain an active schedule and avoid long periods of time being stuck inside, socially isolated and inactive. If you really slow down, are sleeping too much or sleeping in for several hours, that can promote depression. Try to get up early if you can, perhaps with exercise or just going outside to get some air or a little walk, even though it might be difficult initially.

To the extent that natural light might be available, it’s good to take advantage of those days, but the reality is that in most Canadian winters, there’s very little high-quality light to be had. In places like Toronto and Vancouver, most days are grey and overcast so that’s not necessarily a great solution. But it can be helpful to try to get outside and get exposed to natural light as much as possible.

For people with SAD who are in offices, working at a window is very helpful if they can do it. I’ll often write my patients a letter of support to try to get them a window office with natural light.

Diet also matters, and it’s important for people to avoid eating a lot of simple sugars â€“ the kind one finds in junk foods. With winter depression, there’s a tendency to want to eat junk food, which can promote sluggishness, low mood and weight gain which worsens the problem. Trying to replace some of the carbohydrates and sugars with protein can help energize people during the day and frequent, small meals are another good strategy.