London (dpa) - People who are moody, nervous and susceptible to stress tend to have a weaker immune system, according to scientists who studied a group of volunteers said this week.

In the preliminary study, 84 volunteers were injected with a hepatitis vaccine, using only a tiny amount of the infectious agent, to see how their bodies reacted to the virus.

U.S. researchers from the University of Pittsburgh School of Medicine in Pennsylvania gave the participants a psychological test to measure neuroticism, also known as "negative effect".

People with high scores for this trait tend to be moody, nervous, and vulnerable to stress. The research showed the immune systems of neurotic individuals did not respond well to the vaccine.

Previous studies have found that individuals with "negative effect personalities" tend to report more disease symptoms.

The results of the study appeared today in the journal Health Psychology. Dr Anna Marsland also asked participants to give a short videotaped speech in order to measure their physiological response to a stressful event.

As shown by previous research, the immune response of all volunteers was slightly reduced by having to make the speech. But those with the weakest immune response to begin with showed the most reduction.

Neurotic people may be more vulnerable to disease as a result of their susceptibility to stress, said Dr Marsland.

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