There’s no doubt about it, shorter, colder days with less sunshine certainly have an effect on our overall happiness. Just imagine the regions of the world such as Norway, where the sun doesn’t rise above the horizon for an entire 51 days! That’s 51 days living in darkness!
Seasonal affective disorder (SAD) or seasonal depression is a type of depression that lasts throughout autumn or winter months and is believed to be caused by the lack of sunlight, shorter days and lack of warm temperatures. There are multiple hypotheses as to the true causation behind SAD and it seems there is no one true link, rather a combination of factors including:
A disruption in your circadian rhythm
Experts believe that one causation of SAD is linked to a disruption in our natural circadian rhythm, otherwise known as your body clock, which controls your sleep/wake cycle. Your cycle is directly influenced by light or darkness.
If you were to wake around the same time each morning year round, your circadian rhythm will naturally shift with the seasons, but your wake time remains unchanged. Therefore, your sleep/wake cycle can end up misaligning. SAD can be caused by a mismatch in the sleep/wake cycle and the natural circadian rhythm, which is why light therapy and administration of melatonin are used in the treatment of SAD, to attempt to reset the body clock.
Altered levels of melatonin
This misalignment can disrupt the release of melatonin, the sleep hormone, as it is usually slowed down during daylight hours, in order to keep you awake and alert. As the evening goes on, the production of melatonin is increased. In fact, your circadian rhythm controls many aspects of your body functions including blood pressure, mood, metabolism and body temperature.
For night shift workers, their health can suffer dramatically from their natural body clock being thrown out by alterations in sleep patterns. You could picture someone who suffers from SAD as being similar, the shorter duration of daylight alters their natural body clock, with melatonin being produced at a greater rate, therefore causing lethargy and associated negative emotions.
If you suffer from SAD, it is said that you have trouble with the overproduction of melatonin.
Altered levels of serotonin
Less exposure to sunlight has been associated with lowered levels of serotonin. In general, we all have lower serotonin levels in winter. In fact, serotonin has been used in antidepressant medication since their discovery in the 1950s.
Serotonin even has a role to play in helping to convert to melatonin during the darkened hours. It has been recognized that those who suffer from SAD have lower levels of serotonin during the day and have trouble in producing melatonin when needed at night.
The role of serotonin is that it helps to regulate mood, sex drive, memory, emotional behavior, appetite, and the regulation of the circadian rhythms. Serotonin is a happy hormone and when we have an abundance of it we feel content with our lives.
Genetics may play a role
In studies of the patterns of SAD in family members, it was noted that there was an increased prevalence in the first-degree relatives of SAD patients. Particularly, one study of twins estimated that genetic factors of SAD account for 29% of overall variance.
Diagnosis of seasonal depression
There is no one set test in diagnosing seasonal affective disorder (SAD). Rather particular criteria must be met in determining a diagnosis of SAD. The clearest diagnosis is feelings of depression and the symptoms of SAD present at the same time each year, where the temperate begins to plummet and winter kicks in. Your doctor may ask the following questions:
- Do you find that your depression worsens throughout the cooler months, but almost entirely vanishes in spring or autumn months?
- Have you noticed a clear pattern of the timing of these symptoms for at least two years in a row?
- How would you rate your overall lifestyle patterns including exercise, diet, sleeping patterns and self-care? Do these patterns change throughout winter?
- Is it hard for you to go about your everyday activities in the cooler months? Do you find that your symptoms prevent you from carrying out your necessary daily tasks?
- Are you drinking more alcohol or relying on drugs in the colder months?
Your doctor may also carry out basic tests such as blood tests in order to rule out any other condition with similar symptoms.