ABSTRACT
Suicidal behavior represents one of the most complex human behaviors, influenced by the action of several biological, psychological and social factors. The inheritance of suicidal behavior seems to be linked to two main components: the predisposition to psychiatric disorders and the predisposition to impulsiveness-aggressiveness traits. Twin studies compare the similarity of monozygotic (MZ) and dizygotic (DZ) twins. Tryptophan is an essential amino acid for serotonin synthesis and the tryptophan hydroxylase (TPH) is the initial and rate-limiting enzyme in the biosynthesis of serotonin. Monoamine oxidases (MAO) are enzymes involved in the catabolism of amines. The catechol-O-methyltransferase (COMT) is an enzyme involved in the catecholamines' inactivation. The Brain Derived Neurotrophic Factor (BDNF) is a neutrophin involved in neuronal and plasticity of serotonergic and dopaminergic neurons. Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis seems to be linked to suicidal behavior. The HPA axis is responsible for stress response and it is regulated by the corticotrophin-releasing hormone (CRH).
