Seminal studies by pioneers in the study of suicide noted seasonal variations of suicides and attributed this phenomenon to a direct influence on the circuit of the brain of climate variables, in particular temperature. Classical studies point to variations with a peak in spring and early summer.

Many studies have found that there is a spring peak of suicides (especially for males; a spring and autumn peak is often referred to females), but methodological difficulties often hamper analysis. In fact some authors indicated a lack of seasonal variation for suicides.

Affective disorders in general and bipolar disorders as well as unipolar depression may be influenced by seasonality. Some people with bipolar disorder can also have seasonal changes in their mood and experience acute episodes in a recurrent fashion at different times of the year. It has been classically described that some people with bipolar disorder are more likely to experience depressive episodes in the fall/winter and manic episodes in spring/summer. On the other hand, seasonal affective disorder (also called SAD) is a type of depression that occurs at the same time every year. Typically, seasonal affective disorder is a condition where depressions in fall and winter alternate with non depressed periods in the spring and summer. The degree to which seasonal changes afflict mood, energy, sleep, appetite, .food preference, or the wish to socialize with other people has been called “seasonality.” Implications for assessment, treatment and prevention of suicide are discussed during the course of this presentation.