London, Nov 24 (IANS): Permanent stress can activate immune cells that can cause changes in the brain, leading to mental disorders such as schizophrenia, shows a study.

The researchers focused mainly on a certain type of phagocytes, namely microglia. Phagocytes are large white cells that can swallow and digest microbes and other foreign particles.

Under normal circumstances, microglia repair gaps between nerves cells in the brain and stimulate their growth. However, once activated, microglia may damage nerve cells and trigger inflammation processes, the findings showed.

The more frequently microglia get triggered due to stress, the more they are inclined to remain in the destructive mode - a risk factor for mental diseases such as schizophrenia, the study noted.

However, the researchers noted that not every individual who is under permanent stress will develop a mental disorder.

US researchers demonstrated as far back as the 1950s that children born of mothers who contracted true viral influenza during pregnancy were seven times as likely to suffer schizophrenia later in life.

The new study confirmed this hypothesis in animal models.

"The embryo undergoes some kind of immune response which has far-reaching consequences and presumably shapes the future immune system," said Astrid Friebe from Ruhr University Bochum in Germany.

The study appeared in the science magazine Rubin.