Stress is not just an abstract term, it is a real physical response to circumstances that may be physical or emotional. When stressed you secrete hormones and we know that long term exposure to those hormones increases your risk of heart disease, suppresses your immunity, and increases your chances of psychological disorders. If that has sent you in search of ways to lower your stress levels then a new study will add to your enthusiasm for the search because it has shown that the stress hormone cortisol can also damage your short-term memory.
The study looked specifically at corticosterone levels in rats, which is the equivalent of the stress hormone cortisol in humans. The rats in the study were 21 months old which corresponds to a human age of 65 years, which is the age that short term memory lapses, possibly related to cortisol, begin in humans.
The 21 month old rats were compared to four month old rats (roughly equivalent to a 20 year old human). The rats were then classified as having either naturally high or low levels of corticosterone. Then the rats were put through a test of short term memory that involved remembering which way they had to turn at a T-junction in a maze after either 30, 60, or 120 seconds.
The longer the time interval, the worse all the rats did in the memory test. However, older rats with high stress hormone levels remembered the correct direction only 58 per cent of the time compared to 80 per cent success in the rats with low stress hormone levels.
Analysis showed that the rats with higher corticosterone levels had 20 per cent fewer synapses between nerves in the prefrontal cortex, the part of the brain involved in short-term memory. This lack of connection can impair the processing and storing of information. So as long term stress hormone exposure causes shrinkage and death of brain neurons so it takes with it the quality of short term memory. Older rats with low levels of stress hormones showed little memory loss by comparison to the younger rats.
If you remember one thing from that, it should be that allowing yourself to remain stressed is not good for you at any age, but particularly as you age and especially for your brain. Maybe there’s a reason why we remember the happy times, because it is when we are happy that we can remember them.
