A lot of written material has been produced over the years explaining various types of depression and their treatments. Similarly, a lot of data has been produced regarding seasonal affective disorder due to the increased number of diagnosed cases in the recent years. A lot of information is available on line and in books. The information on the internet may not always be the best and precise. Thus a book is more trustworthy than the internet.

SAD or Seasonal Affective Disorder is a kind of depression usually influenced by seasons. It is a subtype of major depressive disorder.
These could be of two types – winter onset and summer onset. Winter onset is the most common one among the two. It begins in late fall and ends with the advent of summer. On the other hand summer onset begins in late spring or early summer and wards off by the beginning of winter.