Playing “shooter” video games weakens the brains of young people and puts them at greater risk of dementia in later life, new research suggests.

A trial in Canada found that those who spent a lot of time playing games such as Call of Duty had less grey matter in a crucial part of the brain.

Scientists behind the research have cautioned doctors against recommending video games as a means of boosting older people’s cognitive function, warning the activity may be harming their ability to retain memories.

Previous research has shown that people with depleted amounts of white matter in their hippocampus, the part of the brain responsible for orientation and for recalling past experience, face a higher risk of neurological illnesses including Alzheimer’s, depression and schizophrenia.

Video games have been shown to benefit certain cognitive systems related to visual attention and short-term memory, but were suspected to damage the hippocampus.

Researchers at the University of Montreal scanned the brains of habitual players of action video games and compared them to non-players, finding the gamers had less grey matter.

"If action video games lead to decreases in grey matter in the hippocampus, caution should be exerted when encouraging their use by children, young adults and older adults to promote cognitive skills such as visual short-term memory and visual attention," the scientists wrote.