ScienceDaily (Mar. 27, 1998) — WASHINGTON - People with lower intelligence before a traumatic experience are more likely to develop posttraumatic stress disorder (PTSD) symptoms, according to the first study to identify a cognitive risk factor for PTSD. Conversely, higher intelligence may protect against the development of PTSD. The research, conducted with 90 U.S. Army and Marine Corps Vietnam combat veterans, is to be published in the April issue of the American Psychological Association's (APA) Journal of Consulting and Clinical Psychology.

Researchers studied the association among precombat intelligence, current intelligence, and PTSD symptoms among 31 healthy Vietnam veterans and 59 Vietnam veterans with PTSD symptoms. Those with PTSD had lower precombat intelligence, fewer years of education, and lower current intelligence. "For a given amount of combat exposure, persons of lower precombat intelligence were more likely to develop PTSD following combat," said the authors. Co-author Richard J. McNally, Ph.D., says "it remains to be seen whether cognitive ability is associated with PTSD symptoms after exposure to other types of traumatic events."

Posttraumatic stress disorder does not lower measured intelligence; the researchers found no significant correlation between PTSD severity and difference between precombat and current intelligence. The authors are careful not to blame the development of PTSD on victims' intelligence levels. "PTSD is caused by traumatic events, not lower intelligence," Dr. McNally emphasizes. "Just as levels of cholesterol influence risk for heart attack, levels of intelligence influence risk for PTSD in people exposed to traumatic events."

The researchers maintain that there may be several possible explanations for their findings. People of lower intelligence may believe they are less able to cope and consequently may feel increasingly overwhelmed and helpless, thereby increasing their risk for PTSD. They suggest that individuals with more cognitive resources may be better able to cope with the emotional impact war-zone exposure has on them. They conclude that trauma-exposed individuals with lower cognitive ability may be targeted for early intervention to prevent the development of chronic PTSD.

Article: "Lower Precombat Intelligence Is a Risk Factor for Posttraumatic Stress Disorder" by Michael L. Macklin, B.A., Linda J. Metzger, Ph.D., Natasha B. Lasko, Ph.D., Scott P. Orr, Ph.D., and Roger K. Pitman, M.D., Veterans Affairs Medical Center, Manchester, New Hampshire and Harvard Medical School, Brett T. Litz, Ph.D., Boston Veterans Affairs Medical Center and Boston University School of Medicine, and Richard J. McNally, Ph.D., Harvard University, in Journal of Consulting and Clinical Psychology, Vol. 66, No. 2.

The American Psychological Association (APA), in Washington, DC is the largest scientific and professional organization representing psychology in the United States and is the world's largest association of psychologists. APA's membership includes more than 150,000 researchers, educators, clinicians, consultants and students. Through its divisions in 50 subfields of psychology and affiliations with 58 state, territorial and Canadian provincial associations, APA works to advance psychology as a science, as a profession and as a means of promoting human welfare.

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