Seasonal affective disorder (SAD) is a subtype of depression with symptoms that occur based on a seasonal pattern. Typically depressive symptoms occur during the winter, but other patterns are possible. For example, depressive symptoms may appear in the spring, or anxiety symptoms may show up in the summer. The potential symptoms of SAD are the same set of symptoms that can occur with other types of depression, although winter depression tends to be more likely to be associated with oversleeping and increased appetite.
People with bipolar disorder who have a seasonal element to their illness may be diagnosed as bipolar I or II with seasonal pattern. Seasonal fluctuations are more common with bipolar II than bipolar I. Spring and summer may trigger the onset of mania or hypomania.
Approximately 6% of Americans experience SAD, while around 14% experience seasonal dips in mood that don’t meet the full diagnostic criteria for a depressive episode. One survey found that 20% or Irish people experience SAD. The exact cause of SAD isn’t clear. Rates of SAD are elevated at higher latitudes that have less light in the winter, which may effect melatonin production by the pineal gland in the brain. This can affect serotonin production, as melatonin is a precursor to serotonin.
Light therapy one option that can be effective for treating SAD. It involves sitting in front of a 10,000 lux light box for 30 minutes or a 5000 lux box for an hour. Times may need to be lower for those with bipolar disorder. It’s recommended to sit 30-60 cm (about 1-2 feet) away from the box, at an angle that allows the light to shine in your eyes without staring directly at it. Light therapy and treatment with SSRIs have been shown to have approximately equal effectiveness.
Getting regular exposure to outdoor light (even on cloudy days) and physical activity may also be helpful.
I live on the wet west coast of Canada, just north of the 49th parallel. The biggest issue in the winter here is that it rains a ton, so the sun doesn’t make an appearance very often. While I find cloudy vs sunny days make a transient difference in my mood, winter doesn’t seem to affect my symptom patterns overall. However, since early on in the course of my illness I’ve had a consistent seasonal pattern of a major drop in mood starting in late August and lasting through September.
I have a light box that I sometimes use in the winter, but I don’t notice much of an effect from it. I actually prefer the warm glow of my Himalayan salt lamp, even though it’s not the right kind of light to be effective for SAD.
Do you have a seasonal component to your illness?
You can find the rest of the What Is series here.