well it's a fairly addictive drug and physical and psychological dependency can creep up on you. your life can begin to revolve around the next joint at a certain point and it can make you apathetic to a depressive routine of not going out much or pushing yourself to do anything other than play videogames and smoke. some people will attest that it aids motivation for them but i find the inverse to be more common. in terms of purely physical detrimental effects it's definitely nbd compared to cigs or alcohol, but knock-on effects from ending up in a sedentary lifestyle and eating poor quality food can be a concern with heavy users, it can also exacerbate depression or anxiety with heavy dependency. you can end up depending on it just to go to the store or do social interaction or even pull yourself out of bed. speaking as a 10+ year stoner who has had better and worse periods with this stuff. ultimately it's a massive reduction in harm compared to say alcohol dependency but people definitely underrated the damage it could do for a while, up until a few years ago where that started seeing some healthy pushback. it obviously has legitimate medicinal applications too but ime self medication can spiral into recreational dependency quite easily.