Seasonal affective disorder is a form of major depression. The symptoms of depression include persistent and excessive feelings of sadness, hopelessness and guilt, isolation and thoughts of suicide (or attempts) as well as physical symptoms such as headaches, low libido, sleep disturbances and gastrointestinal problems. A diagnosis of depression is made when a person suffers from symptoms that last for two consecutive weeks (or longer) and that are severe enough to interrupt daily life. Sometimes the episodes of bipolar disorder may be seasonally-driven, with depressive episodes during the autumn and winter followed by periods of mania during the spring and summer months (or vice-versa).
People with seasonal affective disorder suffer from episodes of depression that coincide with the change of the seasons, and otherwise don't report feelings of depression during the rest of the year. Winter depression sufferers tend to be socially withdrawn, uninterested in their normal activities, have low energy levels and difficulty concentrating. They sleep more and report being tired during the day. As many as 65 percent of SAD sufferers say they're hungrier during the winter months, and three-quarters report weight gain. While it's difficult for a lot of us to pass up a slice of warm bread or a comforting bowl of pasta, as many as seven out of 10 people suffering from SAD report strong and persistent cravings for those mood-boosting carbohydrates [source: Health.com]. Symptoms often begin in early autumn and peak during December, January and February.
Summer-onset SAD, on the other hand, is sometimes called reverse SAD because the symptoms are often the opposite of the more common winter-onset form of the disorder. Summer depression sufferers are more likely to experience agitation and anxiety, increased libido, difficulty sleeping, loss of appetite and weight loss. People with summer-onset SAD find their symptoms usually begin in the spring and peak during the longest months of summertime. Only about 10 percent of SAD sufferers have summer-onset SAD [source: Griffin].