SAD is depression caused by lack of natural light. People who have limited exposure to light, and people who live in northern climates are most likely to suffer from SAD, though many people undergo seasonal variations in mood, energy, appetite and sleep. With SAD, sufferers experience an exaggerated version of these changes. Full-blown SAD can be extremely debilitating; the sufferer finds it difficult to carry out normal activities.
The disease is often undiagnosed because the symptoms are general enough that they can be attributed to a variety of causes. SAD can be treated with or...

SAD is depression caused by lack of natural light. People who have limited exposure to light, and people who live in northern climates are most likely to suffer from SAD, though many people undergo seasonal variations in mood, energy, appetite and sleep. With SAD, sufferers experience an exaggerated version of these changes. Full-blown SAD can be extremely debilitating; the sufferer finds it difficult to carry out normal activities.
The disease is often undiagnosed because the symptoms are general enough that they can be attributed to a variety of causes. SAD can be treated with or...