Some health experts have questioned whether the study's findings are conclusive. Robert MacCoun, professor of public policy and law at University of California at Berkeley, said that while the study was carefully conducted, the results are purely correlational.
"The results must be interpreted cautiously," MacCoun said. "For example, it is difficult to be certain that any comparison between the non-smokers and marijuana smokers actually reflects effects of marijuana, rather than some other differences between the groups."
Experts agreed that the study does not provide evidence that marijuana smoking is healthy for the lungs, but that marijuana is indeed a complex substance.
"I think what is most striking about the results is that we are so accustomed to studies emphasizing, and sometimes exaggerating, how dangerous marijuana is for users' health," MacCoun said. "So this study is a cautionary note that we still have a lot to learn about this complex psychoactive plant."