I don't buy it for a second. Repeatedly inhaling any smoke is not going to be good for you. And that is a tiny portion of smokers, from the same area, presumably smoking a fairly similar strain, as they are from the same part of the world.

If the study had covered a much larger number of smokers and non-smokers and covered a greater portion of the globe, rather than one city, it might carry some weight. But this study means next to nothing.