Experts say the months after Christmas when winter really sets in can be the most difficult for sufferers with Seasonal Affective Disorder (SAD).
SAD is a type of depression that follows the seasons and usually kicks in around autumn when the weather turns chilly and days become shorter.
It is more common in northern geographic regions.
A less common type of SAD, known as summer depression, usually begins in the late spring or early summer, it goes away by winter and experts believe SAD may be related to changes in the amount of daylight during different times of the year.
For many the condition will mean they are more irritable and tired and disinterested in socialising; for others battling with a severe case of the disorder, work may be seriously affected and they withdraw both professionally and socially.
Experts say it can be as bad as any form of depression and according to the American Psychiatric Association, young adults and women appear to be most at risk.
As many as half a million people in the United States may have winter depression. Another 10% to 20% may experience mild SAD.
The symptoms differ according to the whether the sufferer is prone to winter or summer SAD.
Winter victims may see a change in appetite, especially a craving for sweet or starchy foods, weight gain, heavy feelings in the arms or legs, a drop in energy level, fatigue, a tendency to oversleep, difficulty concentrating, irritability, increased sensitivity to social rejection, and an avoidance of social situation.
Summer depression can include include poor appetite, weight loss and insomnia.
Both types of SAD may also include some of the symptoms that are present in other forms of depression including feelings of guilt, a loss of interest or pleasure in activities normally enjoyed, ongoing feelings of hopelessness, and physical problems, such as headaches.
The symptoms appear year after year at about the same time and it is thought that up to 5% of the U.S. experiences severe SAD, another 20% faces a milder version of the winter blues and another 25% has a symptom or two but remains totally functional.
Treatments include bright light therapy, negative air ionization and in severe cases even antidepressants.
Experts advise those who are sufferers to seek professional help rather than struggling to cope.
Many standard techniques can be helpful in keeping stress levels down such as maintaining some sort of structured schedule, doing some form of exercise and getting out of the house for some part of the day.
Being positive is essential and sufferers are advised to consider work demands by recognising their limitations during these periods and managing their work load accordingly.