SAD (seasonal affective disorder), also known as winter depression, winter blues, or seasonal depression, is a mood disorder subset provoked by reduced daylight hours during fall and winter. People who have normal mental health throughout most of the year experience depressive symptoms at the same time each year.
SAD is characterized by irritability, oversleeping, increased tiredness, changes in appetite, and reduced motivation to participate in social activities. If you’re like most people with SAD, your symptoms start with the reduction of seasonal light and continue into the winter months, sapping your energy and making you feel moody. Less often, SAD causes depression in the spring or early summer.
Although experts were initially skeptical, this condition is now recognized as a common disorder. The American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders (DSM-IV & DSM-5) was changed and is no longer classified as a unique mood disorder but is now a specifier called with seasonal patterns for a recurrent major depressive disorder that occurs at a specific time of the year.
SAD’s prevalence in the U.S. ranges from 1.4% in Florida to 9.9% in Alaska. Countries closest to the equator report almost no incidences of SAD, whereas extreme northern and southern countries, have high incidences. This is mainly due to the fluctuations in daylight hours as the seasons’ change, disrupting a person’s circadian rhythm—or internal clock—which controls a person’s physiological response to light and darkness.
To reiterate, if you have SAD, you may:
- Feel sad, grumpy, moody, or anxious.
- Lose interest in your usual activities.
- Eat more and crave carbohydrates, such as bread and pasta.
- Gain weight.
- Sleep more but still feel tired.
- Have trouble concentrating.
Women are four times more likely than men to experience SAD due to the disorder’s association with female hormones. Individuals who have been previously diagnosed with depression, or those who have a family history of depression, are at an even higher risk for SAD.
The reduction of daily light exposure causes shifts in hormone and chemical levels in the brain. The two main hormones responsible for SAD are serotonin—responsible for ‘feel good’ mood and melatonin—responsible for inducing sleep. Some people are more sensitive than others to the reduction of natural light during the day and will produce more melatonin and less serotonin during the autumn and winter months. These chemical shifts disrupt the circadian rhythm, worsen moods, and decrease energy.
The most common treatment for SAD is light therapy, which consists of daily exposure to light that mimics outdoor light, leading to increases in serotonin levels in the brain that will help lift moods and relieve other symptoms. It is best to start light therapy early in the fall before symptoms appear or they become to get too intense and interfere with school work and other daily activities..
“Interestingly, the symptoms of SAD are not limited to only reduced seasonal daylight. Similar symptoms are now common for millions of people all year round caused by our now predominant indoor lifestyle.”