it can weaken ur lungs so ur more at risk for illnesses like bronchitis or infection. ive done alot of researching and that is my main question too, any long term side affects, and so far i havent found anything, at least not anything really bad, there have never been ANY deaths directly related to marijuana as in ODing, but other than the weakening ur lungs and maybe some affects on ur memory (not sure on the permanence of that tho, i know ur short term goes to shit when ur high but it returns when u come down) just dont over-do it and ull be fine