What Stress Does to Mental Capability

Modern humans live a busy, hectic, and multi-tasking life full of uncertainties. It doesn’t take long for this to become stressful. Stress releases adrenalin that pumps us up and makes us more capable in the short term. Adrenalin even helps us remember. Stress also releases hormones called corticosteroids, which include compounds like cortisone and hydrocortisone. They too are useful for short-term emergencies. But long-term, corticosteroids damage the brain and diminishes mental capability. One study monitored blood levels of cortisol, the most abundant corticosteroid in humans, in 57 healthy volunteers once each year for 5-6 years. Subjects varied consider-ably in the extent of their stress, as indicated by blood levels of cortisol, and also by psychological test measures of stress. People with high-cortisol levels that increased each year had nearly half the memory performance capability of the people with mod-erate levels of cortisol that decreased each year. Brain scans revealed that people in the high-stress group had a smaller hippocampus, the part of the brain that governs the conversion of a temporary memory into a lasting one. The hippocampal shrinkage is of special concern because other studies have shown that the hippocampus also helps to regulate cortisol levels. Damage to the hippocampus can lead to a vicious cycle of even more cortisol release and added hippocampal damage. In another study, brain-scans of older humans with a history of chronic stress showed they had a shrunken hippocampus. Thus, it was no particular surprise when researchers found that stressed subjects performed worse than controls on delayed-recall memory tests of line-drawings and a spatial memory maze test. I recently had the chance to visit with U.C. Irvine’s James McGaugh, who is a pio-neer in research on stress effects on memory. Early on in his research, he reported that a strong memory is created when a single stress event is presented to previously un-stressed rats. Adrenalin is what creates the memory enhancement.. Ordinarily, this can be a good thing because it makes it more likely that the things that caused the stress will be remembered and avoided in the future.rnOne of his key findings from research in rats is that some animals show great sen-sitivity to stress by releasing huge amounts of adrenalin and cortisol. But other rats barely react at all. Most human studies lump all the individual data together in a group average, and that obscures individual differences. This is important, because people vary a lot in the way they respond to stress, both psychologically and in the release of adrenalin and cortisol. Dr. McGaugh and I agree that individual differences might be the reason post-traumatic stress disorder (PTSD) occurs in some people, while other people are not so affected by the same level of stress. The people who get PTSD may well be hypersensitive and prone to release large amounts of adrenalin and cortisol. If so, screening of PTSD patients might reveal which ones will be most responsive to adrenalin-blocking therapy with propranolol, as I discussed earlier when discussing PTSD. It also suggests that screening of troops before going into battle could identify which ones are likely to need preventive medication or post-traumatic therapy. Actually, the military is very much aware of these issues. Their current emphasis is to administer helpful drugs as soon after trauma as possible. Hormone responses to stress operate at all ages. But older people have accumulat-ed a lifetime of stresses, and their nervous systems have learned more or less habitual ways to respond to stress. The learning ranges from growing hypersensitive to stress-ors, or by learning coping skills. Hormone and mental effects vary accordingly. How much memory deficit will occur as one ages could depend on how much life stress has been endured and how one has learned to react to stress. Reducing stress should not only make for better living but also better mental capability.rnAs a Senior citizen, I am increasingly aware that aging has its own set of stressors. I know too that stress of earlier years can linger, even magnify, and accumulate as the years go by. Have I learned to become hypersensitive or to cope? Learning how to re-duce stress can help sustain good mental capability in old age, not to mention making life more enjoyable. Yoga, anyone? Dr. Bill Klemm, a.k.a. “Memory Medic,” is a neuroscientist at Texas A&M University who operates a blog, Improve Your Learning and Memory. He has two recent books, one an e-book for students, Better Grades, Less Effort, and the other a comprehensive general-audience paperback, Memory Power 101rn