Smoking weed is unlikely to cause acne, but it may lead to some behavioral changes that could make existing acne worse.
It can in some cases, THC raises your testosterone which could cause more acne but it should not cause to much more if any at all.
THC use is associated with small increases in testosterone . This increase in T appears to decline as THC use increases. I could not find the article I read on it so I just googled lmao