So what does that actually mean? "In general, our findings showed that cannabis use over 20 years was unrelated to health problems in early midlife," the study authors write. "Clear evidence of an adverse association with cannabis use was apparent for only one domain, namely, periodontal health."This is great news for cannabis lovers, but the study does have limitations. All of the marijuana use in the study was self-reported, and it's not clear how great humans are at accurately remembering how much or often they smoke pot. There's also the fact that this study only includes data for participants up to age 38, so we can't make any claims about how true these findings are for weed users beyond that age.And, as The Washington Post points out , the study doesn't consider the possible mental health effects of marijuana. The lead author on this study, Madeline H. Meier, PhD, even used the same dataset that was used in an infamous 2012 study to suggest that chronic pot use may lead to a decrease in IQ. But, remember, subsequent studies have failed to find that same strong effect (and it's probably a more complicated story than we think).More than anything else, this study suggests that we still have plenty of research to do.