If you ask Sha Carri Richardson 100 metre sprinter I think the answer would be no, probably the same with Michael Phelps, one of the greatest ever swimmers.
But what about driving whilst under the influence on cannabis, I recently read an article on crazeco.com.au: "Unimpaired Medical Cannabis patients can lawfully drive in Tasmania"

Very little research has been done since medical cannabis became legal in Australia, many patients are getting frustrated with the lack of effort on the government's part.
The pharmaceutical industry is also quite complacent with any research, which it's not surprising as it competes with their own products.

CAMBRIDGE, MA—Shedding light on a promising way to provide relief from the chronic condition, a study published Monday by Harvard University found that medical marijuana was an effective treatment for long-term pain over Jerry Garcia’s death.

Performance enhancement plant? Or inhibitor?
So much negative media about the effects of cannabis and here we see clearly, it doesn't inhibit this young woman's abilities! fastest woman in the world?

In the following interview Zoe Sigman discusses the endocannabinoid system with emphasis on the cannabinoid CBD.
Zoe is a writer/researcher for the CBD project.
I'm very skeptical about the medicinal efficacy of any isolated cannabinoids believing that nature knows best and people have ulterior motives.

This is a recent article from the Byron Echo reflecting the frustrations of Australian citizens;

The good oil
Colin Thornton, Federal

Now that medicinal cannabis is finally legal you would think that it would be freely available. But doctors who have tried to access it on behalf of needy patients have found themselves forced through so many legal hoops and obstacles that it becomes almost impossible. And then, if it is actually obtained, the (imported) product is prohibitively expensive.