Suzana Herculano-Houzel

The reality of psychosomatic stress

Column_359 The reality of psychosomatic stress

How annoying it is to hear from others that a problem you feel on your skin is “just in your head”. It’s good that science has freed us from other people’s beliefs, including this one: health problems that are “just psychosomatic”.

Well, they’re so real that even rats suffer the effects of stress. What kind of problems disturb rats’ sleep, you ask? Several, all related, as they are for us, to the feeling of powerlessness and lack of control. One of them is the stress of having their territory invaded and losing the fight to the invader. In cases of social defeat, the losing rats suffer from tachycardia, high blood pressure and even a purely emotional fever, which doesn’t respond to antipyretics.

How is it possible to have a fever because of stress, and even more so a fever that doesn’t respond to treatment? A scientific tour de force by neuroscientist Kazuhiro Nakamura’s group at Nagoya University in Japan recently revealed the brain circuit responsible. As you might expect for something as subjective as the feeling of social defeat, the emotional fever in the rats begins in the cerebral cortex, in prefrontal, associative areas – which means they do much more than process sensations or movements. These are the parts of the cortex that make our lives complex and flexible, and that adjust our behavior and adapt it to our external and internal reality.

According to the study published in the prestigious journal Science, the medial part of the rats’ prefrontal cortex has a direct line to the hypothalamus, the most anterior structure of the vertebrate brain, which in turn has a direct line to the body. In the event of a social defeat, the medial region of the hypothalamus triggers the sympathetic nervous system, which causes everything together: tachycardia, hypertension – and even fever, due to increased heat generation in brown fat tissues in the body.

This is the kind of fat that babies and those who live in the cold have a lot of, but we all have some. Under stress, these reserves start to be used purely for heating, which is completely different from the increased generalized heat generation of fever, caused by a different part of the hypothalamus. The antipyretics that act on one and fight the fever of infection don’t act on the other, and so the emotional fever doesn’t go down.

Not all fevers are the same, but that doesn’t make some any less real – or any less important.

Originally published in Folha de São Paulo in May 2020.

More Posts

pt_BRPortuguês do Brasil