War and the Brain

A fascinating study on the psychological effects of war just came out in JAMA. Researchers measured the cognitive abilities of soldiers after serving in Iraq. What they found is consistent with our current models of stress, which predict that chronic stress (of the sort found in Baghdad) will damage the hippocampus, a part of the brain essential for learning and memory. But the news wasn't all bad. After returning from battle, soldiers had faster reaction times.

A large study of Army troops found that soldiers recently returned from duty in Iraq were highly likely to show subtle lapses in memory and in ability to focus, a deficit that often persisted for more than two months after they arrived home, researchers are reporting today.

But the returning veterans also demonstrated significantly faster reaction times than soldiers who had not been deployed, suggesting that some mental abilities had improved.

The slight deficit, often unnoticed by the soldiers, could make it difficult for some of them to learn and remember information as quickly as they are accustomed to, the authors said. These lapses are more common but less disabling than emotional reactions to combat like depression or post-traumatic stress disorder, the researchers said, and in many cases probably reflect a natural adaptation to life in Iraq, with the reaction time strengthening at the expense of some other mental functions.

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I haven't seen the paper, bu there is a well-known phenomenon, the Yerkes-Dodson law, about the effects of stress on cognitive functioning. Low levels of stress may improve performance on complex cognitive tasks, while moderate and high levels will reduce performance. On simple tasks, however, high levels of stress may improve performance. I suspect that's part of the story here. The experience of being in a combat zone improves simple vigilance and reaction time, but hampers performance on more complex reasoning, attention, and memory tasks.