Seasonal affective disorder is a type of winter depression which affects millions of people every winter. It's a type of depressive disorder.

The disorder usually begins when you're a young adult. It's also more common in women than in men.

What causes SAD is unclear, but it may have to do with the amount of sunlight you receive. Although SAD can affect people anywhere, it becomes more common the farther north or south you are from the equator - these areas of the planet experience decreased daylight for months at a time. In some people, recurring episodes of depression may occur in the summer rather than in the winter.

Although there's no cure for SAD, there are treatments to help you successfully manage the condition so that you can go through the seasons of the year with relative comfort.

• Anxiety
• Depression

Signs and symptoms

SAD is a cyclic, seasonal condition, which means signs and symptoms are present only during a particular season of the year and then go away. Most of the time, the signs and symptoms of SAD appear during the winter and recede during the spring and summer.

But there are some exceptions to the rule. Some people have worsened signs and symptoms of depression in the spring. Other people experience periods of mania or hypomania, a less intense form of mania, during the summer. Characteristics of mania may include persistently elevated mood, hyperactivity and inflated self-esteem.

If you've been through two annual cycles with the following signs and symptoms, you may have SAD:

• Depression

• Loss of energy

• Anxiety

• Irritability

• Headaches

• Increased sleep

• Loss of interest in sex

• Overeating, especially foods high in carbohydrates

• Weight gain

• Difficulty concentrating and processing information