I thank you for helping me clarify my question.  I do want to see if there is a marginal difference between the physiological and psyche.  

How would I locate the Canadian study that you have referred to? 

Search in PUBMED for Staci A Gruber and Deborah Yurgelun-todd and Nadia Solowij.  Several behavioral and neuroimaging papers suggest chronic cannabis is not nearly as harmful as other substances, but not as benign as the decriminalization crowd would like to believe, either.

Contact Dr. Carl Hart of Columbia, he has run clinical studies on users of all types of drugs including marijuana. Most studies that showed "damage" to brain or health were not run well. Cannabinoids boost neurogenesis, the growth of new brain cells in the adult brain.

There is a substantial body of evidence that long-term use of cannabis (especially if initiated during adolescence) is a significant risk factor for developing psychosis or schizophrenia.

See attached papers.

It may also cause an amotivational syndrome.

See the link.

http://www.ncbi.nlm.nih.gov/pubmed/23438696

I have not yet come across anything which empirically states that cannabis use is quantifiably correlated with negative psychosis in a healthy population sample. What I have found are papers re cannabis use tend to focus on samples whom exhibit variations of pre-existing tendencies of negative psychosocial expression. For example, one person may develop one set of outcomes after cannabis use while another person may develop an entirely separate set of outcomes when using the same cannabis sample. Individual factors which affect outcome such as biological and chemical reactions to cannabis intake will and do influence results, let alone samples with pre-existing psychosocial tendencies. Researchers whom have a pre-existing attitude toward cannabis use naturally tend to find evidence which support their belief system. As researchers, we are required to maintain a non-biased stance in order to further understanding of a rather old substance but considered socially new, due to the relaxation of state and Federal controls. What we should do is finance a meta analytic study of cannabis research which includes a large population parameter so subjects whom have preexisting conditions which may effect the outcome are included but statistically accounted for among the larger healthy population. Without a meta sample of the population, I presently conclude that articles which cherry pick factors regarding cannabis use to be specious simply due to the inability of our community to access cannabis for use in a true experiment model. So there.