June 19, 2010 by Evie Bentley.
We’ve known for ages that far more females than males suffer from depression and anxiety disorders, but it is frequently hypothesised that this is not the true state of things. This is because, in Western industrialised cultures, it is more acceptable to admit vulnerability especially psychological vulnerability if one is female, not male. The macho nature of these cultures is, if you like, a confounding variable. However, there could be more to this than social and cultural relativism.
A recent interesting finding in rats shows that females are definitely more sensitive to stress. Their brain cells respond far more strongly to the precursor to corticosteroid stress hormones, a neurochemical called corticotropin-releasing factor, CRF. Female rat neurons are activated by CRF, male rat neurons adapt to it and less stress hormones are produced.
But does this rat behaviour also happen in humans? Well, we don’t know; but we do know that CRF regulation gets disrupted in human stress-related psychological disorders, so there could be a similarity, although one needs always to be very careful in generalising between species.
January 16, 2010 by Cara Flanagan.
Long-time depression researcher Eva Redei recently reported some of her latest findings. She has spent decades breeding rats who are severely depressed (mating depressed rats with depressed rats so you get ‘who are believed to be the most depressed rats in the world’ (!!)). This meant she could identify genes linked to depression. Next she exposed a different group of rats to stressful situations for two weeks which enabled her to identify the genes that consistently were associated with a poor response to stress.
The big news is that there was no overlap between the depression genes and the stress genes. This suggests that the idea that stress causes depression may be wrong. And, furthermore, she claims the reason antidepressants are often ineffective is because they treat stress and not depression and she has now shown that the two are not linked, though they may co-occur. So that’s one reason why antidepressants only work for some people (those suffering from stress and depression). Before you say ‘ah well, this is just an effect in rats’, Redei claims that rat brains are very similar to human brains, so it is reasonably to draw analogies. It also may explain why we like cheese. (No, that last bit was a joke).
December 8, 2009 by Evie Bentley.
Diathesis-stress is an example of nature AND nurture, as it can be interpreted as a gene or genes switched on by environmental factors. Recently it’s been suggested that being lonely and stressed could affect the expression of cancer-linked genes, triggering their action. The research has been done in the USA on rats, comparing those kept in isolation with those living in groups. The former group had over three times the frequency of breast tumours than the latter group, and their breast tumours were also more aggressive and deadly. The isolated rats also produced more stress hormones and were more reactive to stressful situations. Rats, like ourselves, are social animals and so being isolated is likely to cause stress.