This sounds very interesting. I know weed affects peoples sleep cycles, specially at the beginings of regular use, but my personal opinion is that these people are more likely to smoke weed as a form of unconcious self medication, therefore making the user question him or herself - the chicken or the egg.
Please don't try to use prohibitionist rhetoric in your thinking process. Their positions are so biased as to be totally unreliable and reasonably excluded from consideration it their entirety. From brain damage, to causing cancer, to amotivational syndrome, to the gateway theory, etc, etc, etc, all based on bias, and supported by 'scientific' studies designed to produce the results to support the bias they've proven themselves liars.