Criminal behavior, lack of guilt, and irritability are typical features of antisocial personality disorder. Evidence suggests that a low-activity variant of the MAO-A gene predisposes to adult antisocial behavior in men, especially in those who faced early adversity 1–4 . Catechol-O-methyltransferase enzyme metabolizes dopamine and other monoamines. Its gene, the COMT-gene, occurs in two forms: a high-activity form and a low-activity form. They associate these variants with differential abilities of the prefrontal cortex, especially working memory. People with low-activity form may have a more efficient prefrontal cortex, likely because of the greater dopamine level in the synaptic space 5,6 . We have associated serotonin transporter gene variants with neuroticism and a predisposition to depression. The variants may also influence individual response to SSRIs8. APOE4 gene is a risk factor for Alzheimer’s disease (compared to APOE2 and APOE3).