London: Exposure to a type of bacteria found in soil boosts happiness levels and could help restore healthy immune functions in people who are depressed and prone to infection, says a study.

British scientists led by Chris Lowry at Bristol University treated lung cancer patients with the bacteria, named 'bacterium Mycobacterium vaccae', and found improvement in their quality of life, reported the online edition of BBC News.

However, they said more work is needed to determine if the bacteria has anti-depressant properties through activation of serotonin neurons - a chemical in the brain that helps maintain a 'happy feeling', and seems to help keep our moods under control by helping with sleep, calming anxiety and relieving depression.

Mice exposed to the bacteria made more of the brain's "happy" chemical serotonin, the researchers told the journal Neuroscience.

The study may help understand how the body communicates with the brain and why a healthy immune system is important for maintaining mental health.

"They also leave us wondering if we shouldn't all spend more time playing in the dirt," Lowry said. (IANS)