Extra stress can lead to memory loss, say Edinburgh researchers

Too much stress may help contribute to memory loss as we get older, researchers from Edinburgh University have suggested.

A study into mice has found that once stress levels reached a certain point, the animals were less able to remember how to navigate a maze – although small amounts of stress actually helped memory. The discovery could help in developing drugs to treat age-related memory disorders, the scientists believe. The researchers, led by Dr Joyce Yau at the university’s Centre for Cardiovascular Science, looked at how two receptors in older brains reacted to the stress hormone cortisol, which has been linked to increasing forgetfulness as we grow older. They found that one receptor was activated by low levels of cortisol, and that this actually helped memory. Once levels of the stress hormone were too high, however, they affected a second receptor and activated brain processes that contribute to memory impairment. The memory recall problem was reversed when the receptor linked to poor memory was blocked, according the study, which was published in the Journal of Neuroscience. The study helps explain why too much stress over time interferes with the normal processes in storing memories, while a little bit of stress can actually help us remember emotional memories, the researchers say. “While we know that stress hormones affect memory," said Dr Yau, "this research explains how the receptors they engage with can switch good memory to poorly-functioning memory in old age. “We now know that lowering the levels of these stress hormones will prevent them from activating a receptor in the brain that is bad for memory. Understanding the mechanisms in the brain, which affect memory as we age, will help us find ways to combat conditions linked to memory loss.” This study was funded by the Medical Research Council, and the researchers – with help of a Seeding Drug Discovery award from the Wellcome Trust, are currently investigating a new chemical compound, 11beta-HSD1, which is involved in producing stress hormones within cells. They hope this could be used to develop a drug to slow the normal decline in memory linked to ageing, or possibly even improve memory in older people.

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