Suicide is a major social and public health problem, one of the leading causes of death, a major complication of different psychiatric disorders that can evoke great suffering in patients and their families, and places a financial burden on society as a whole. Suicidal behavior and suicide are frequently associated with various psychiatric disorders and personality traits. However, most psychiatric patients never attempt suicide, indicating that aside from psychiatric diagnoses, other socio-cultural, environmental, biological and genetic factors are important risk factors for suicide. The biological and genetic contributions to suicide are still not completely understood, and the heterogeneity of the underlying neurobiology makes such investigations particularly difficult. Molecular basis of suicidal behavior is assumed to involve the changes in different neurotransmitter and neuroendocrine systems (primarily in the serotonergic and noradrenergic systems, the activity of the hypothalamic-pituitary-adrenal axis (HPA). Therefore, research on suicide, which is the major and the most dramatic consequence of suicidal behavior, should be linked to biological characteristics of suicidal behavior, to find biomarkers that might predict suicidal behavior, in order to prevent suicide.