There is no solid research on prevalence of seasonal affective disorder (SAD) . Some evidence indicates that people who live in northern latitudes may be more frequently affected.
When onset is in winter, the following symptoms often occur:
- General depression symptoms
- Social withdrawal
- Craving for foods high in carbohydrates or other appetite changes
- Weight gain
Spring and Summer Symptoms
When onset is in the spring or summer, the following symptoms are more likely:
- Weight loss and poor appetite
- Increased sex drive
Infrequently people have a reverse form of seasonal affective disorder, experiencing the following symptoms, that relate to elevated mood:
- Persistently elevated mood
- Increased social activity
- Elevated mood or enthusiasm beyond normal range
The following factors may play a part in seasonal affective disorder, with no clear cut single cause likely to emerge.
Melatonin, a hormone that affects sleep is suspected by some, as the body naturally produces more of it during winter. Serotonin, a brain chemical, may also play a part, as reduced light causes a drop in serotonin levels.
The body’s natural clock, called the circadian rhythm , may be disrupted by the short days and long nights of winter by and cause depression.
Other general causes of depression may also apply.
Psychotherapy, light therapy and medication are all used to treat Seasonal Affective Disorder. A mental health professional may indicate the need to begin taking an antidepressant several weeks before the onset of symptoms.