What is concerning about spliff is the tendency to facilitate descent into abnormal mental states.
I enjoy good relations with a few healthcare professionals and the general consensus is, at this point, spliff has more potential benefits to explore than bad effects, so it makes sense to explore it, never overlooking the continuous use has been linked with some serious mental inbalances and even some physical syndromes.
Just a few days ago, here, on Lemmy, there was a lemming talking about a strange condition where continuous use over decades can trigger extremer pain and discomfort episodes, due to deposit of substances on fat tissue.
Tobacco is a proven killer, yes, but who knows what weird side effets we may be yet to discover connected with mary jane.