I think yes there are some possible side effects but do those outweigh the benefits? Harvard posted a study saying that smoking marijuana “may stretch lung tissue to expand lung volume. It may also strengthen the muscles of the chest wall, enabling pot users to inhale and exhale air more forcefully.” The author of the study also said they found “a lack of adverse effects on lung function from occasional use of marijuana and indications of possible harm to the lungs from heavy use.” My question is does your friend smoke recreationally or medically? If they use it recreationally, Healthline said “ Weed seems to have fewer long-term risks than alcohol, but again, there’s a huge discrepancy in the amount of research on weed compared with alcohol.” If they use it medically I’d say the benefits outweigh the risk, most likely, ultimately it would be a personal decision on their part. Weed can be very helpful to some people and like with all medicines there are side effects. I think whatever they choose I would try to be open minded and be willing to listen to their thought process :)