Sussex University researchers have come up with findings that may help flu sufferers.
They found that it may not be just the physical symptoms that leave people with flu feeling tired and unwell.
Their findings may also enable drugs companies to minimise the depressive side-effects of some medicines.
Neil Harrison, of Sussex University, said: “When we have the flu we feel a bit fatigued, a little bit tired – perhaps our mood is a little bit reduced.
“This sort of constellation of different symptoms is known collectively as ‘sickness behaviours’.
“People have assumed that these are just natural consequences of having an infection.
“But it seems that whatever the cause of the infection is, the symptoms are exactly the same.”
The broadly similar psychological feelings experienced by those with a variety of infections suggest that the feelings are not caused by the infection itself but by the brain’s response to it.
Healthy volunteers were injected with a vaccine for typhoid. One side-effect of the vaccine is mild flu-like symptoms.
They were then scanned using a functional magnetic resonance imaging scanner (fMRI) to monitor which parts of the brain were inflamed while performing simple tasks like looking at emotional facial expressions.
The researchers found that the people who felt the most negative change in mood after the typhoid vaccination showed the greatest increase in activity in a part of the brain called the subgenual cingulate.
A control group received a placebo instead of the typhoid vaccine. The control group volunteers’ subgenual cingulates showed less activity.
Dr Harrison said: “What’s remarkable about this is that this individual brain region is the area that’s most implicated in major depressive illness.”
The findings offer hope for patients who suffer from depression as a side-effect of their medical treatment such as chronic hepatitis C sufferers who are given interferons.
Dr Harrison said: “This is a very effective treatment but it’s associated with the onset of major depressive illnesses.
“In some cases this can be associated with suicidal thoughts.”
The research may enable drugs companies to develop ways of mitigating the depressive side-effects, although as Dr Harrison said: “It’s extremely early days at the moment.”
