WHAT IS SAD? What are the links between light and seasonal depression? Seasonal affective disorder (SAD) is a specific type of recurring depressive illness that manifests in an annual pattern, usually from early-to-late fall and subsiding with the longer, sunnier days of spring. Some people have the milder form, called subsyndromal-SAD (S-SAD), also known as the winter blues. This mild “winter blues” form causes minor problems in people’s lives but not the total disruption that full-blown SAD causes.
Researchers aren’t sure what causes seasonal affective disorder. Three main theories have been put forth, and there is contrasting evidence both for and against each of these theories: the Melatonin Hypothesis, the Phase Shift Hypothesis, and the Serotonin Hypothesis.
- Melatonin Hypothesis
- The Melatonin Hypothesis argues that SAD is due to too much melatonin being secreted in response to the long, dark days of winter. Some studies have supported this theory, while others have disputed it.
- Phase Shift Hypothesis
- Advocates of the Phase Shift Hypothesis, proposed in 1986, contend that in patients with SAD, circadian rhythms [see Sleep & Circadian Rhythm Disorders section] have been desynchronized to the light-dark cycle, and that appropriately timed bright light reverses SAD Symptoms by realigning these rhythms. Again, there is evidence on either side of the debate.
- Serotonin Hypothesis
- In the Serotonin Hypothesis, the idea is that serotonin levels in the brain are much lower during the winter months in patients with SAD than they are either in people without SAD or in SAD patients during the spring and summer months. This hypothesis came about from researchers observing that SAD patients tend to feel energized after carbohydrate consumption (which increases serotonin levels), whereas people without SAD generally feel more lethargic after eating carbohydrates. Whether serotonin is ‘the cause’ of SAD or not, there is currently a wide body of evidence to suggest that it does play a major role in the disorder.
Other neurotransmitters (dopamine and noradrenaline, for example) may also be involved, as well as other hormones (thyroid, corticotrophin-releasing hormone). The role of these other neurotransmitters and hormones, though, requires further research.
WHAT ARE THE SYMPTOMS OF SEASONAL AFFECTIVE DISORDER?
The symptoms of seasonal affective disorder manifest themselves differently for different people.
The typical symptoms include decreased mood and low energy level, social withdrawal, low sex drive, anxiety, irritability, and inability to concentrate or be productive at work.
The “classic” SAD symptoms, which are considered atypical symptoms of non-seasonal depression, are sleep problems, including changes in sleeping patterns (oversleeping and having poor sleep) and appetite changes (increased appetite, carbohydrate cravings, and subsequent weight gain).
In children and teenagers, the symptoms are slightly different from those for adults. These symptoms include inability to concentrate as in adults, but also irritability, crying spells, anxiety, low energy and fatigue, difficulty in getting out of bed for school, and a lowering of grades and self-esteem.
Because these symptoms mirror the symptoms of laziness, Attention Deficit Disorder (ADD), learning disabilities, or the stereotypical behavior of teenagers, it is important for parents to note whether these symptoms recur year after year during the fall and winter months, and whether they go away in the spring.
THE BASICS ABOUT BRIGHT LIGHT TREATMENT RESEARCH
A lot is known about bright light treatment and light therapy research; it involves the use of a special type of light fixture that produces much brighter light than regular indoor lighting. Visit our Research section for complete details on Seasonal Effective Disorder (SAD) Treatment.