You’ve probably heard of seasonal affective disorder. Often referred to as SAD, it’s a form of depression that happens seasonally, usually arising in the late fall and winter. But have you heard of reverse seasonal affective disorder? Also called Summer SAD, and it’s what we often think of as the “summer blues,” or depression that occurs in the summer months.

Winter SAD and Summer SAD are related to seasonal changes in the amount of sunlight we’re exposed to—and both have strong connections to sleep. People with SAD in winter or summer appear to have trouble adjusting their sleep clocks to the seasonal changes in sunlight and darkness. Scientists think both types of seasonal affective disorder may be linked to changes in the body’s production of melatonin, a hormone that is produced by exposure to darkness, and an important hormone for sleep. (Other seasonal factors are believed to play a role, too, including temperature.)

SAD—the wintertime version of seasonal affective disorder—is thought to be provoked in part by a lack of sunlight, which creates an overproduction of melatonin, and important sleep hormone. These seasonal light and melatonin changes can affect our circadian rhythms, which help regulate our sleep. People with Winter SAD often are inclined to sleep a lot more than they typically do. Melatonin is also involved in the body’s production of serotonin, a hormone that plays a major role in our mood.

All of these biological changes are thought to contribute to the depression and other symptoms associated with Winter SAD, including:

  • Low energy
  • Feeling a need to hibernate
  • Increased appetite
  • Trouble concentrating

Summer SAD, on the other hand, may result at least in part from too much sunlight. The long days and shorter nights of summer translate into less time for the body to make melatonin. Like when the body produces too much melatonin, too little of the hormone can cause problems with sleep, disruptions to our circadian rhythms, and changes to the body’s serotonin. People with Summer SAD often experience:

  • Insomnia
  • Restlessness and anxiety, in addition to feelings of depression
  • An excess of energy, which makes it hard to settle down for sleep at night
  • Loss of appetite
  • Trouble concentrating

Here’s where geography comes in: studies show Winter SAD occurs more often in people who live in the northern parts of the United States, while Summer SAD is more common among people who live in southern regions. (From a global perspective, Winter SAD appears more frequently in places further away from the equator, whether north or south; Summer SAD is more likely in regions near the equator, where the sun is strongest.)

Winter SAD is a much better studied and more well known condition than Summer SAD. Scientists currently think Winter SAD is also much more common, with about 10 percent of all seasonal affective disorders occurring in the summer.

If you think you may be suffering from SAD, talk to your doctor. There are four major treatments usually prescribed including medication, light box therapy, cognitive behavioral therapy and vitamin D. We tend to think of summer as a carefree, happy time. But for some people, Summer SAD may make this light-filled season more complicated and difficult.


Written by Caitlin Reynolds