The Truth About Seasonal Affective Disorder

Can Light Be Harmful?

Now to springtime. "April is the cruelest month," T.S. Eliot famously said. This poetic insight makes sense, given the harmful impact of increased light in springtime. Again, most people think of SAD only in terms of winter depression, but springtime mania should not be ignored, especially because mania frequently reflects mixed states, when depression and mania occur together, and mixed states are linked with the highest risk for suicide. Indeed, a century ago Kraepelin showed a clear suicide spike in April, far higher than other months. Winter suicide rates are quite low; this has been replicated over and over.

The harmful effect of increased light may have something to do with another underappreciated fact. As Howard Kushner explained in his classic book, American Suicide, the highest suicide rates in the United States have always been in the sunny West, specifically California, and particularly the sunniest part of California: San Diego County. It's been this way for 100 years, despite all kinds of cultural and social changes. Obviously suicide is an olio of many ingredients, but could a biological catalyst be the dark side of SAD: too much light?

Whatever the case, we know that too little light can cause depression in people who are sensitive to it, especially those who already have mood diseases. However, let's not forget that too much light is, in many ways, just as bad.

January may be an unhappy month, but April is the cruelest.