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January 2011



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Genes And Environment May Interact To Influence Risk For Post-Traumatic Stress Disorder

Article Date: 04 Nov 2009 – 1:00 PST

Individuals who experience both childhood adversity and traumatic events in adulthood appear more likely to develop post-traumatic stress disorder than those exposed to only one of these types of incidents, according to a report in the November issue of Archives of General Psychiatry, one of the JAMA/Archives journals. In addition, the risk was further increased in individuals with a certain genetic mutation.

Although 40 percent to 70 percent of Americans have experienced traumatic events, only about 8 percent develop PTSD during their lifetimes, according to background information in the article. PTSD is a complex anxiety disorder that involves re-experiencing, avoidance and increased arousal following exposure to a life-threatening event. “In addition to the obvious effect of environmental factors, PTSD has a heritable component,” the authors write. Recent studies estimate that genetic factors account for approximately 30 percent of the difference in PTSD symptoms.

Pingxing Xie, B.S., of Yale University School of Medicine, New Haven, Conn., and VA Connecticut Healthcare Center, West Haven, and colleagues studied 1,252 individuals who had experienced childhood adversity (including abuse or neglect), adult trauma (such as combat, sexual assault or a natural disaster) or both. Participants age 17 to 79 (average age 38.9) were interviewed and assessed for a variety of psychiatric and substance use disorders. DNA was extracted and used to differentiate between versions of a particular polymorphism or gene mutation-known as the 5-HTTLPR genotype-previously found to be associated with emotional response after stressful life events.

About one-fifth of the participants (229, or 18.3 percent) met criteria for PTSD. A total of 552 of the 1,252 participants (44.1 percent) experienced both childhood adversity and traumatic events in adulthood. These individuals were more likely to have a lifetime diagnosis of PTSD than were those who experienced trauma in only one life stage (29 percent vs. 9.9 percent).

“Although the 5-HTTLPR genotype alone did not predict the onset of PTSD, it interacted with adult traumatic events and childhood adversity to increase the risk for PTSD, especially for those with high rates of both types of trauma exposure,” the authors write. The genotype may influence the way the brain processes the neurotransmitter serotonin, affecting an individual’s anxiety levels and changing the way neurons react to fearful stimuli, they note.

“It was only in the group of subjects who could be characterized as having had the highest rates of trauma exposure (i.e., in both childhood and adulthood) that an impact of 5-HTTLPR could be detected,” the authors conclude. “This suggests that there may be many neurobiological (including genetically determined) ‘buffers’ to PTSD; only in instances of extreme and/or repeated trauma exposure (which, it should be pointed out, characterizes those trauma ‘types’ with the highest conditional risk for PTSD, e.g., domestic violence and military combat), in which these buffers are overwhelmed, can the impact of specific genes such as 5-HTTLPR be detected.”

Arch Gen Psychiatry. 2009;66[11]:1201-1209.

Archives of General Psychiatry

Associated Conditions of PTSD

By Harold Cohen, Ph.D.

Persons with PTSD often have other disorders as well, which makes it difficult for clinicians to diagnose the PTSD. In particular, major depression and substance abuse are common in people with PTSD. There may also be an increased risk of panic disorder, agoraphobia, obsessive-compulsive disorder, social phobia and somatization disorder. Scientists are not sure to what extent these co-occurring disorders are present before or come after the traumatic event and the development of PTSD.

When exposure to trauma has been long-standing (as for badly abused children), persons may develop certain enduring patterns of behavior or traits. These include difficulty in trusting others, irregular moods, impulsive behavior, shame, decreased self-esteem and unstable relationships. Many of these traits are also seen in persons with borderline personality disorder, and people with this disorder often have histories of childhood physical and sexual abuse, which are possible causes for PTSD.

Persons with posttraumatic stress disorder (PTSD) also often have physical symptoms. They may go to a primary care physician with many physical complaints, rather than psychological concerns. Studies have also shown that people with PTSD are at increased risk for a number of medical conditions, such as hypertension and asthma.

Significant interpersonal difficulties are common in persons with PTSD. Symptoms of estrangement, irritability and anger, or associated depression, may take their toll on a person’s relationships. Persons with PTSD may find it difficult to talk about symptoms with those who did not go through the same trauma. Sometimes, guilt about surviving or about acts done in order to survive can also cause increased isolation and tension in interpersonal relationships.


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