I think there are many ways to answer that question. THC is a chemical which interacts with the brain. Depending on the influences of certain hormones and neurotransmitters plus environmental influences would determine how one reacts to it. Just to sample the people in college I know who smoked, some were unproductive others weren't. The productive smokers are no less productive than productive non-smokers. In terms of health, smoking anything isn't good for the lungs. Regarding your subject line, I think for those of us who are environmentally influenced to lead unproductive lives, those people would find a way to be unproductive one way or the other. Weed, alcohol, or anything else amplifies what the individual decides to do with their time. You know what I mean?