To what extent are genetic and environmental factors linked with the development of posttraumatic stress disorder?

Purpose
PTSD is a disorder that may develop in people who have been exposed to traumatic events or stressors. Four main types of symptoms of PTSD can be distinguished: affective, cognitive, behavioural and somatic. Although much research has been done, the exact cause of the development of PTSD is still unknown. The risk of susceptibility to PTSD is probably increased by environmental and genetic factors.

Review
According to the meta-analysis Broekman et al. there are certain genes which may promote PTSD. It seems that specific polymorphisms in the serotonin transporter gene (5-HTT), GABA receptor, dopamine receptor (DRD2) and dopamine transporter (DAT) might be involved in the development of PTSD. On the other hand, environmental factors have also been investigated. There is a diversified group of these, including among others manmade catastrophes, natural disasters, SOT transplantations and experiences of migration. Vulnerability to PTSD increases with the duration of exposure, the power of the stress and individual sensitivity.

Conclusions
Our results indicate that there must be a relationship among a number of factors in the development of PTSD. It is possible when strong environmental factors affect a vulnerable organism with predisposing genes that the disorder is going to develop considerably. However, despite a lot of research which has already been done, the exact cause of PTSD is still unknown and requires further study.