Example 3: Long-term cannabis users at midlife In 2002 we reported that young cannabis users had elevated risk for psychosis [31]. In 2007 we reported that cannabis users developed periodontal disease, beyond the effects of tobacco use [32]. Our Dunedin Study is well suited to tracking the health of sustained heavy cannabis users as they age. In 2012 there was strong interest in our report in PNAS [33, 34] that cannabis users who began using as teens and continued into adulthood showed a variety of cognitive declines, culminating in a loss of 8 IQ points on formal testing from age 11 to age 38. In January 2013, this paper was again prominent as result of a misguided critique attributing our findings to socioeconomic factors [35] to which we published a successful empirical rebuttal [36]. In January 2014, this paper was once again in the news, as result of legalisation of cannabis in Colorado, and because it was featured in an AMA report that recommended against legalisation. Lost in the hyperbole was our observation that evidence of harm is clearest for
