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Researchers from Rockefeller University (USA) have found that single exposure of rats to a 30 minutes stressful episode caused widespread methylation (an epigenetic phenomenon) in the hippocampus, a brain area known to be involved in several mental disorders like depression.and schizophrenia. Repeated exposition to the same stressful episode day after day did not cause further methylation, suggesting that the animals adapt. Fluoxetine (Prozac) was only somewhat efficient in removing this epigenetic mark.
Lead researcher Richard Hunter said:
There was a thought that the genome project would reveal all in neuropsychiatric disease, but that has proven not to be the case. Epigenetics has become much more interesting because it allows us to look at how gene expression is changed by environmental events, explainable in part by histone modifications.
Source: Science Daily.
Research paper: Richard G. Hunter et al., Regulation of hippocampal H3 histone methylation by acute and chronic stress. PNAS 2009.
2 comments:
The scientists are hinting that stress can cause mental ilness but what they are inflicting on the rats is way beyond a normal stress.
In the wild a rat would get away from something trying to hold it or get eaten. Being restrained for 30 min a day is by no means the kind of recuring stress that rats would have adaptive epigenetic responses to. In human terms it's probably more comparable to daily prolonged torture than emotionally stressful events.
Stress producing epigenetic responses would result in changes that would be adaptive for the environment, ie adaptive for those specific stressors. As all humans have always undergone emotional stress in social interactions I don't see how they would have evolved to go haywire >1% of the time. In other words schizophrenia is too common in poeple who have lived fairly normal lives to be analogous to the rat experiment.
The epigenetic switch to a metabolism adapted to low food availability could be switched on by accident, eg pregnant woman goes to work without eating a breakfast which leads the fetus to epigeneticaly switch to a food scarcity mode. That might be a bad thing when the chid is born into aworld of abundant food; yet it would be a good thing in the right environment.
I still wonder what schizophrenia could possibly be good for, what social or physical environment could schizophrenia be adaptive in. Schizophrenic men do not father as many children as normal men and they are not rare like genetic diseases.
30 mins one single day is enough, further stress of the same kind does not change anything. And I'd say in humans is more akin to a brief preventive arrest of the same duration. Humans and rats are very similar: humans are not born to be in prison either.
In other words schizophrenia is too common in poeple who have lived fairly normal lives to be analogous to the rat experiment.
I don't think "fairly normal lives" are exempt from dramatic trauma at all, right? Birth alone (in hospital conditions at least) is highly traumatic: being separated from your mother for hours after birth is certainly much more severe than being restrained for 30 mins.
And that's just the beginning.
A "fairly normal life" for our biology and psychology would be that of a Hadza, not civilization in any case. We are only badly adapted to this, the same we are only badly adapted to cold, dark climates.
But sure, I strongly suspect that usual hospital birth is the binning of a rough life.
Anyhow, the case is that stress and/or repression may trigger psychological problems and does it via epigenetics, not genetics.
I still wonder what schizophrenia could possibly be good for, what social or physical environment could schizophrenia be adaptive in.
Is not good. As I see it it's a severe deterioration caused in the same way as an immune disease, like allergies or other autoimmune diseases, that can kill you just out of "curing" you. What normally may be adaptative in some cases may become destructive out of overreaction or maldapted reaction.
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