London - Children exposed to high levels of infection could be more prone to depression and psychosis when they grow up, warn researchers.
They found that children with high everyday levels of a protein released into the blood in response to infection were at greater risk of depressive illnesses in adulthood.
New findings suggest that the immune system plays an important role in mental health by ‘cranking’ up the body’s responses and increasing the risk of subsequent mental illness.
Scientists led by Cambridge University analysed blood samples from 4 500 volunteers at age nine and followed up at age 18 to see if they had experienced episodes of depression or psychosis. The samples were examined for signs of previous infection.
When the immune system is mobilised, the bloodstream is flooded with proteins such as interleukin-6 (IL-6), a tell-tale marker of infection, which help fight and remove it. Even after recovery the blood carries trace levels of these proteins – known as “inflammatory markers”.
The team found that children with high everyday levels of IL-6 were nearly two times more likely to have experienced depression or psychosis than those in with low levels.
Study leader Dr Golam Khandaker from the department of psychiatry at Cambridge University said: “Our immune system acts like a thermostat, turned down low most of the time, but cranked up when we have an infection.
“In some people, the thermostat is always set slightly higher, behaving as if they have a persistent, low-level infection.
“These people appear at a higher risk of developing depression and psychosis. It’s too early to say whether this association is causal, and we are carrying out additional studies.”
People with depression and schizophrenia are known to have a much higher risk of developing heart disease and diabetes, and elevated levels of IL-6 have previously been shown to increase the risk of both.
The study – which was published in the journal JAMA Psychiatry – says anti-inflammatory drugs should be investigated to see if they could treat illnesses such as depression. Treatment with such agents leads to levels of inflammatory markers falling to normal.
Previous research has suggested that anti-inflammatory drugs such as aspirin used at the same time as anti-psychotic treatments may be more effective than anti-psychotics alone.
Professor Peter Jones, head of the department of psychiatry at Cambridge, said: “Inflammation may be a common mechanism that influences both our physical and mental health.
“It is possible that early life adversity and stress lead to a persistent increase in levels of IL-6 and other inflammatory markers in our body, which in turn increase the risk of a number of chronic physical and mental illnesses.” - Daily Mail