Cannabis punishment

Assalamu alaikum wa rahmatullahi wa barakatuh My question is in regards to the punishment of consuming cannabis. Many scholars are of the view that the punishment for smoking cannabis is the same as drinking alcohol, including prayers not being accepted (rewarded) for 40 days. However, I wonder how they can be the same if cannabis can be consumed if for medicinal purposes while alcohol can never be consumed, even for medicine. This suggests that they are not exactly the same, and therefore the punishment may not be identical? I have read that some jurists regard the impermissibility of cannabis as lower than the impermissibility of alcohol (both still impermissible of course). Could you please advise? JazakAllah khair