Cannabis..

Men with a history of cannabis use had less cognitive decline from early adulthood to late midlife compared to men without a history of cannabis use.

 Among cannabis users, neither age of initiation of cannabis use nor frequent use was significant.

Researchers at the Univerity of Copenhagen studied about the relationship between cannabis use and age-related cognitive decline.

The findings pointed out that there are no significant harmful effects of cannabis use on age-related cognitive decline. This is quite contrary to what was believed. 

Meanwhile, a recent study found that low doses of Tetrahydrocannabinol (THC), the main active ingredient in cannabis, showed to reverse conventional signs of brain aging in mice. 

Just a thought.