Dirt 'boosts happiness'

Exposure to dirt may be a way to lift mood as well as boost the immune system, UK scientists say.

Lung cancer patients treated with "friendly" bacteria normally found in the soil have anecdotally reported improvements in their quality of life.

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

Common antidepressants work by boosting this brain chemical.