People with symptoms of SAD often experience 2 or 3 years of the condition before they are diagnosed.
First described in 1984 by Dr. Norman Rosenthal from the US, seasonal affective disorder (SAD), also known as seasonal adjustment disorder, is a form of depression that can occur at certain times of the year.
Mind, a UK organization that provides advice and support to individuals with mental health problems, notes that the majority of people with SAD experience the condition during winter months. Some people can be affected in reverse and experience depression during the summer months, but this is very rare.
According to Beth Murphy, head of information at Mind, the condition is often undiagnosed, making it difficult to know how many people suffer from the disorder. People with symptoms of SAD often experience 2 or 3 years of the condition before they are diagnosed.
However, Murphy says estimates show that around 10% of the population in Northern Europe experience milder symptoms of the condition, while 2% experience more severe symptoms.
According to the Cleveland Clinic, approximately 500,000 people in the US suffer from SAD, and around 10-20% of the US population suffer from milder forms of the disorders.
But regardless of the number of people worldwide who suffer from SAD, experts say that doctors appear to have lack of awareness of the condition.
Helen Hanson, chair of the Seasonal Affective Disorder Association (SADA) in the UK and a sufferer of SAD, told Medical News Today:"I would say that we are still finding that the medical profession don't seem to have sufficient awareness of the illness and particularly of its complexity. A pattern of presentation with depression needs to be noticed before a diagnosis can be made and general practitioners who do not have SAD on their agenda can still miss it completely.
So what are the signs of SAD to look out for?
Symptoms of SAD
According to Murphy, SAD can begin at any age. However, it is more likely to develop before the age of 21, and is twice as likely to develop in women than in men.
Other symptoms include:
Previous research has suggested that SAD may be caused by lack of light in winter seasons.
- Lack of energy for everyday tasks
- Weakened immune system
- Lack of concentration
- Overeating and weight gain
- Alcohol or drug abuse
- Feelings of guilt and worry
- Sleep problems
- Reduced libido
- Social and relationship problems.
Potential causes of SAD
It is unknown what the exact causes of SAD are, but previous research has suggested that since the condition occurs during the change in seasons, changes in light may trigger the disorder.
Murphy explains that when light hits the retina at the back of the eye, messages are sent to the hypothalamus - the part of the brain responsible for sleep, appetite, sex drive, temperature, mood and activity.
"If there's not enough light, these functions are likely to slow down and gradually stop," says Murphy, adding:
"Some people seem to need a lot more light than others for their body to function normally, and are therefore more likely to develop SAD symptoms when there are low levels of light."
It is thought that levels of serotonin - a neurotransmitter in the brain - may also play a part in the cause of SAD.
Low serotonin levels have been found in people who suffer from depression, particularly during winter months. This suggests that people with SAD may have an impairment in the brain's system that releases and absorbs serotonin.
Research has also found that people with SAD produce higher levels of the hormone melatonin in winter, compared with people who do not have the condition.
The pineal gland in the brain produces melatonin when we are exposed to darkness, which causes us to sleep. When it is light, the production of melatonin stops, making us wake up.
But Murphy says research has shown that melatonin is unlikely to be the only cause of SAD.
"We know that if someone with high melatonin levels is exposed to bright light, their melatonin levels drop to normal," she says. "However, trials have shown that even after their melatonin levels have returned to normal, most people continue to experience the depressive symptoms of SAD."
Previous studies have also shown that SAD could be caused by disruption to the body clock. It has been suggested that those with SAD may have a faulty body clock that is unable to set the body's circadian rhythm to daylight hours, causing tiredness and depressive symptoms.
Additionally, Murphy says reports have suggested that, like other forms of depression, SAD could be triggered by traumatic life events, physical illness, a change to diet or medication or use/withdrawal from drugs or alcohol.
'I couldn't make the connection to darkness and dull weather'
SADA's Helen Hanson first experienced symptoms of SAD at the age of 13. She had winter flu and felt depressed and anxious for many months.
Her doctor prescribed antidepressants, and she found she felt better as the summer months approached.
"I probably had sub-syndromal SAD, as did my mother, for most of my adult life. But it showed up as an inability to get up on winter mornings, a deep dislike of November and December and general feelings of despair which I did not recognise as seasonal," Hanson explains.
She explains that there were no recurring symptoms until she reached her late 30s, when she moved from a light modern flat to a dark Edwardian terraced house.
Hanson developed winter flu, which was followed by labyrinthitis - an inner ear infection. These conditions kept her at home for weeks, during which time she experienced sickness and dizziness.
"I developed a post-viral depression, which gradually got better, but its symptoms came back suddenly and unexpectedly the following September without any accompanying illness. I more or less came to a halt," she says.
For the next 3 years, Hanson attempted a series of self-help remedies to try and beat her depression, but these did not help. She says:
"I knew that I hated darkness and dull weather but didn't make the connection because I didn't know there was one.
Eventually, I saw a new doctor and she spotted a pattern. She pointed me towards SADA. I went to their annual general meeting and realised with huge relief that I was amongst fellow sufferers and that we all had something with a name. I was not mad after all."
On the next page, we discuss the treatment options for SAD and discuss why there is lack of awareness surrounding the condition.