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Past Abuse and Genetics Combine to Raise PTSD Risk
> 3/18/2008 1:16:22 PM

Individuals who suffered abuse as children respond differently to adult traumas and are more likely to develop post-traumatic stress disorder in the wake of a distressing event, especially if the earlier abuse was of the physical or sexual variety. A particular genetic polymorphism also leaves them susceptible to that chronic condition, and a recent study surveying low-income patients in the Atlanta hospital system notes that childhood trauma, in combination with this variation, creates the greatest risk of an individual developing PTSD after disturbing personal events. The "nature vs. nurture" debate appears to be somewhat irrelevant in PTSD cases as the two elements, while damaging on their own, have an exponentially higher degree of influence when occurring in tandem.

PTSD is said to be "30 to 40 percent" genetic in origin, and identical twin studies have confirmed the considerable influence of inheritence on later stress disorders. But the responsible bio-system has yet to be mapped out in full even as extensive research continues on a daily basis. The polymorphism uncovered by this study is most likely a key element in the PTSD equation - FKBP5 plays a predictably crucial role in the body's stress-response system by determining how tightly stress hormones bind to their own receptor cells. Early disturbances in this process, such as those created by disruptive personal traumas, may lead to permanent changes in the system itself. Beyond emotional disturbance, the extreme physiological imbalance created by such profound levels of stress in combination with abnormally high levels of related hormones creates a system defined by dramatic instability and far more susceptible to the development of chronic stress conditions.

The variation has also been linked to major depression, which is very often comorbid with PTSD and most likely applies to a considerable number of the abused individuals who participated in the recent study. They were drawn from a pool of poor, urban and primarily minority individuals due to the greater presence of early life stressors in low-income, high-crime environments. One researcher asserted that PTSD rates in inner city neighborhoods are "as high as among war veterans," and the study seems to confirm this statement: more than 80% of participants reported experiencing major trauma; 30% had a friend or family member who became a murder victim; 1 in 3 had been abused as children; at least 1 in 4 qualified for a full PTSD diagnosis.

"Protective" variations on the FKBP5 stress receptor also exist, furthering the belief that the gene plays a very pivotal role in determining stress response. Individuals with this variation registered almost no PTSD even in the presence of early abuse or later trauma. Interestingly, neither the aversive FKBP5 variation nor the previous abuse factor led, independently, to a significantly higher PTSD rate in the face of later incidents. Only in combination did these two variables create a statistical jump, and it was considerable: the disorder was more than twice as common among individuals who qualified for both. Why are these two issues so toxic when they occur together, and why is their influence not more significant in isolation? How common is this particular genetic polymorphism among the general population, and what can the victims of child abuse take from the study's findings? Only further research can answer these questions with confidence.

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