Stress has been proven to be bad for physical health. Researchers from Ruhr University Bochum, however, have uncovered that it can also be bad for mental health.
Led by Dr. Georg Juckel from RUB's LWL university clinic, researchers explored the cause of mental disorders by focusing on a type of phagocyte known as microglia. Under normal situations, this cell repairs damage between the brain's nerve cells, stimulating their growth. However, once activated, microglia also has the ability to damage nerve cells, triggering an inflammation response.
According to the study, as microglia is more frequently subjected to stress, the longer it stays in destructive mode, resulting in a heightened inflammatory response that increases risks for mental disorders like schizophrenia.
"We see this very clearly in patients suffering from multiple sclerosis or Alzheimer's. The brain areas affected by inflammation or neurodegeneration are surrounded by a circle of microglial cells," described Juckel.
In patients with schizophrenia, microglial cells are higher in number compared to what healthy individuals have. The high number of microglial cells in destructive mode causes deterioration in neurons' synaptic links, which is why schizophrenia patients feature dramatically reduced regions of grey matter.
Does this mean anyone who's stressed is automatically at higher risk of developing a mental disorder?
Not necessarily.
While chronic stress will still take its toll on anyone, not every person under permanent stress develops a mental disorder. The researchers suspect it has to do with how embryos develop in the womb. Previous research have demonstrated that babies born to mothers who got sick from true viral influenza while they were pregnant were seven times likelier to develop schizophrenia as they age. RUB researchers were able to confirm the study using animal models, proving immune responses an embryo experiences during development can have far-reaching consequences that determine an individual's future immune system state.
"Originally, the brain and the immune system were considered two separate systems. This, however, is not true," added Juckel.
Direct connections are formed from the brain, connecting to organs part of the immune system. At the same time, immune cells can migrate to the brain, carrying out various tasks like getting rid of damaged synapses.
An additional example that supports the idea of a brain-immune system connection lies in treating mental conditions, where 20 to 30 percent of patients involved in treatments utilizing immune system mediators were diagnosed with depression.
The study's researchers are now working on exploring the damaging effects of microglial cells in destructive mode in detail.
