Cortisol is a hormone that occurs naturally in the body. It's vital to human survival, helping humans stay alert when danger lurks and to think fast when good decisions are needed quickly. And cortisol isn't harmful in moderate doses, even spikes during instances of stress are a mostly harmless part of the normal human condition.
But prolonged periods of cortisol spikes -- whether due to chronic anxiety, depression or the stress from a string of several worrisome life events -- is bad for the body. Too much of the important hormone can weaken the immune system and break down muscle, bone, and connective tissues. An excess of cortisol has also been linked to weight gain and high blood pressure.
And as Iowa University researchers recently demonstrated, it hobbles short-term memory loss too.
Researchers linked elevated amounts of cortisol levels to the gradual loss of synapses in the prefrontal cortex, the area of the brain responsible short-term memory. The connection was backed by lab experiments involving mice.
In the experiment, older rats with high cortisol levels performed poorly in navigating their way through a maze, whereas old rats with low levels of cortisol, as well as young rats with all different levels of cortisol, were able to navigate the maze with ease.
Thus, the researchers concluded the connection between cortisol and short-term memory loss only surfaces after the age of 65.
"Stress hormones are one mechanism that we believe leads to weathering of the brain," said co-author Jason Radley, psychology professor in psychology at Iowa.
The study is scheduled to be published this week in the Journal of Neuroscience.
It's not all bad news for the aging, however. Earlier this year, a different study showed high self esteem can help suppress spiking cortisol levels and ward off the hormone's negative health consequences in the elderly.