The shallow depth of research has left clubs and unions in Europe wary of recommending CBD as a supplement. But with strong anecdotal evidence of positive effects encouraging more use, some players believe it will become the norm.

"Boys take protein, creatine, all kinds of stuff to help them and I think because CBD is from cannabis everyone links it to the drug that's illegal," British and Irish Lions and Scotland fly-half Finn Russell, who has invested in a CBD brand founded by his former Glasgow team-mates Adam Ashe and Grayson Hart, tells BBC Scotland.

"The more people start using it, then clubs will become more aware of it and start doing their tests and it will be a matter of time until it becomes like a protein shake or something like that."

Former Scotland and Saracens lock Jim Hamilton believes, over time, there will be a "culture shift" towards CBD.

"It needs more people to start seeing good side effects, more papers and reports being written about it. America are five years in front of us when it comes to this," he told BBC Scotland.

"It's about evolution going forward and trying things that are safe to enhance my life, my family's life. And being able to move the game forward and the way we take supplements and medicine in future."