Stress hormones impair memory
High serum concentrations of cortisol may be responsible for stress
induced memory loss, a team of researchers from Zurich has found.
They compared the effects of oral cortisol and placebo in a randomised
trial and found that the cortisol group did worse in tests of recall
than controls. The research was prompted by animal research suggesting
that learning was enhanced in animals given glucocorticoids.
In this study, the 46 subjects were randomised to take either 25
mg cortisone (which produced circulating cortisol concentrations
equivalent to natural concentrations of cortisol at times of stress)
or a placebo. They were all asked to memorise 60 nouns, each of
which were presented on a computer screen for four seconds. Both
groups were then tested for free recall (write down all the words
you remember) and recognition (how many of the following words were
on the list). The subjects were also tested for delayed recall,
24 hours after the initial presentation.
Subjects who were given 25 mg cortisol immediately before their
recall test showed a significant deterioration in performance compared
with those who took a placebo. Cortisone administration at other
stages of the experiment showed no significant difference between
the two groups. This suggests, say researchers, that physiological
response to stress does not impair the "learning" aspects of memory
but only the free recall of information. There was no significant
difference between the treated and untreated group in their ability
to recognise words presented.
Cortisol is one of the hormones produced by the adrenal cortex
in response to stress. Previous research has suggested that exogenous
cortisol impairs human overall memory performance, and long term
hypercortisolaemic states such as depression, Cushing's syndrome,
and old age are known to have strong associations with memory impairment.
"Elevated glucocorticoid levels may induce impairments in such
stressful conditions as job interviews, combat, courtroom testimony
and examinations," the authors conclude (Nature Neuro-science
2000;3:313-4 (April.)).
Helen Morant, Clegg scholar, BMJ
studentBMJ 2000;08:131-174 May ISSN 0966-6494
