The notion that psychological stress, and especially posttraumatic stress disorder, can damage the architecture of the human brain is a disturbing notion.
But there is scientific evidence to support it—and the evidence is growing.
During the past few years, for example, various scientists have reported that PTSD patients have smaller hippocampi than normal. These findings suggest that the psychological stress of PTSD is powerful enough to shrink the hippocampus. Smaller hippocampi have also been noted in depressed persons, which in turn may possibly be due to stress as well (Psychiatric News, May 19, 2000).
And now Yutaka Matsuoka, M.D., Ph.D., head of adult mental health at the National Center of Neurology and Psychiatry in Kohnodai, Ichikawa, Japan, and colleagues have found that cancer survivors who experience only one of the symptoms of PTSD—intrusive recollections—have a smaller left amygdala. The investigation was reported in the October 1 Biological Psychiatry.
"This is an intriguing study," David Spiegel, M.D., associate chair of psychiatry at Stanford University School of Medicine, told Psychiatric News. "It is novel to have differences in amygdala volume related to PTSD symptoms in cancer patients."
Matsuoka and his coworkers first recruited 76 subjects who had already survived more than three years since breast cancer surgery. They then took a question regarding PTSD intrusive recollections from the Structured Clinical Interview for DSM-IV Axis I Disorders and modified it slightly so that it was more appropriate for cancer survivors.
The question was this: "Did you think about cancer-related events when you did not want to, or did thoughts about cancer-related events come to you suddenly when you did not want them over a period of four weeks or more?"
They then asked this question of their 76 subjects: 35 (46 percent) answered yes, and the remainder (54 percent) answered no.
The researchers then used magnetic resonance imaging to measure total amygdala volume and volume of the left amygdala and of the right amygdala in each of the subjects. The total amygdala volume was significantly smaller in the subjects who had experienced intrusive recollections than in the subjects who had not, the investigators found. What’s more, this significantly smaller total amygdala volume appeared to be due to a smaller left amygdala, not to a smaller right amygdala. These findings continued to be statistically significant even after the scientists took possibly confounding factors such as age, height, handedness, and a history of major depressive disorder into consideration.
"These results suggest a difference in volume of the amygdala of cancer survivors according to whether they have cancer-related intrusive recollections," the researchers concluded in their study report. The results also suggest, but certainly do not prove, that the psychological stress of having cancer might be enough to shrink the left amygdala.
And how might psychological stress shrink the left amygdala? Conceivably through intrusive recollections because, as the researchers pointed out in their report, "the amygdala is critically involved in the formation of enhanced explicit memory for emotionally arousing events." Still, the psychological stress of having cancer might shrink the left amygdala via some other means, and a diminished amygdala might then lead to intrusive recollections.
"It is more likely that the volumetric alterations of the amygdala precede the cancer-related intrusive recollections," the scientists speculated.
These findings do not have any immediate implications for clinical psychiatrists, Matsuoka told Psychiatric News. But they do have a possible future one, he pointed out—"I think that the left amygdala may become a possible target for the development of a treatment strategy against intrusive recollections in cancer survivors."
Moreover, he said, the findings "represent an important step in integrating medical illness [such as cancer] with a field that was previously the domain of neuropsychiatry."
The study was financed by the Japanese Ministry of Health, Labor, and Welfare; the Japanese Ministry of Education, Culture, Science, and Technology; and the Foundation for Promotion of Cancer Research in Japan.
An abstract of the study, "A Volumetric Study of Amygdala in Cancer Survivors With Intrusive Recollections," is posted on the Web at www-east.elsevier.com/bps. ▪