VANCOUVER -- A study by researchers at the University of British Columbia suggests that while the main psychoactive ingredient in marijuana causes laziness, adding a medicinal component of pot doesn't change that behaviour.

Lead author Mason Silveira says the study done on rats involved giving them THC, the intoxicating part of cannabis, and having them choose between an easy or hard task to earn sugary treats.

Silveira says that under normal circumstances, most rats who preferred the more difficult task to get more rewards switched to the easier option when given THC.

However, the PhD candidate in the school's psychology department says while the finding was not surprising, adding the same ratio of a pain-relieving ingredient called cannabidiol didn't block the so-called slacker effect.

He says the study, published today in the Journal of Psychiatry and Neuroscience, suggests that while some people consider marijuana as a panacea for various ailments, the findings highlight a need for more research.

He says that could allow people who use medicinal marijuana to enjoy the benefits of cannabis without its effects on their cognitive abilities.