Genetic markers in suicidal and non-suicidal veterans with combat-related posttraumatic stress disorder, Chapter 4

Posttraumatic stress disorder (PTSD) is a complex polygenic psychiatric disorder, precipitated by an exposure to a traumatic event. The risk factors for PTSD include, besides traumatic experience, other biological, genetic, environmental factors, and adversity in early life. Genetic studies in PTSD are still scarce. Combat-related PTSD is especially pervasive form of PTSD, frequently associated with suicidal behaviour. Various markers of serotonin (5-HT), dopamine, noradrenalin, hypothalamic-pituitary-adrenal axis function, brain derived neurotrophic factor (BDNF), and catechol-o-methyltransferase (COMT) have been proposed as the possible markers of PTSD and/or suicidal behaviour. Our study determined polymorphisms of the genes for monoamine oxidase (MAO-B), dopamine-beta-hydroxylase (DBH), COMT, BDNF, serotonin transporter (5-HTT) and serotonin 5HT2A receptor in male Croatian war veterans with combat related PTSD, subdivided into non-suicidal and suicidal subjects. There were no significant differences in the frequencies of the genotypes or alleles for MAO-B, -1021C/T DBH, Val158/108Met COMT, Val66Met BDNF, 5-HTTLPR and 102T/C 5HT2A between suicidal and non-suicidal veterans with PTSD. Our results did not support the hypothesis that these genetic variants contributed to the risk of suicidal behaviour in combat- related PTSD. Since both suicidal behaviour and clinical features of PTSD are heterogeneous and complex, the research of the risk genes is associated with numerous methodological difficulties, especially with the problem of detecting a significant effect. The identification of subjects prone to suicidal behaviour is important for the prevention of suicidal attempts and proper treatment interventions, and therefore future studies should elucidate the relationship between candidate genetic risk factors and suicidal behaviour in the large homogenous sample of veterans with PTSD.