Brain imaging studies suggest that those with a postive outlook also have a stronger immune system.

The pre-frontal cortex of the brain is involved in how individuals respond emotionally to events. Previous research has suggested that those with more activity in the right prefrontal cortex are more likely to have a negative response to events.

The left hand side of the pre-frontal cortex is associated with positive emotional responses. Researchers at the University of Wisconsin-Madison have worked with 52 individuals aged between 57 and 60 to see how activity in the pre-frontal cortex is linked to the immune system.

Each of the participants was vaccinated against the flu virus and the antibody response of the immune system was tracked. They were also asked to recall and describe events that made them happy, and events that made them angry or sad. Meanwhile, activity in the pre-frontal cortex was monitored by imaging. Those with the most activity in the left side of the pre-frontal cortex appeared to have the strongest immune responses. This supports the theory that positive thinking can perhaps protect against disease.

Source

Proceedings of the National Academy of Sciences on-line September 2003