Hello everyone. We started this course by talking about how the cancer patient or the veteran with PTSD or the family with a child with seizures or autism, do not have the information that they need to weigh the risks and benefits of cannabis products. Of course that's completely unfair. The goal for module four is to provide a summary of the health risks of cannabis at a general level, and also to provide information about how to administer and dose cannabis to minimize risks. Of course, understand that this is critical to weighing the risks against the benefits. Up coming modules will cover the potential benefits for specific types of medical disorders. Look, it's tricky to be an honest broker of information about the risks of cannabis. The U.S. has a long history of exaggerating the risks of cannabis. More recently, it's fair to say that there has been an effort by some in the industry, to minimize risks and exaggerate the benefits. To make it more difficult science can be a messy business. Making it hard to clarify some of the risks. Having said that in my experience, the majority of people agree about the majority the risks. For example, most of us agree that cannabis use can impair driving, and agree that driving while impaired from cannabis or any other drug or alcohol is dangerous. At the same time we might disagree, about whether or not legalization has resulted in an increase in motor vehicle crashes and fatalities. In fact the data are not clear on this point. We may not agree about whether cannabis use has a causal link to psychosis. Hopefully we all agree that until we know for sure, young people, especially young people with a history of psychosis, family history psychosis should stay away from cannabis. Finally, regardless of whether cannabis use causes negative changes in the brain, I think most of us can agree that cannabis can negatively impact learning and memory in young people. As scientists, policy makers and healthcare providers, whether we condone the use of cannabis or not, I hope we can all agree that giving people who are already using it or planning to use it, information about how to reduce risks and side effects is a good idea. On that note, the last lecture of this section summarizes an academic paper on dosing and rules of administration with suggestions about how to reduce undesirable effects and maximize the benefits. All these sets the stage, for the next series of modules on how to apply this information, to specific groups of patients. I hope we can all find some common ground in this module. I hope you enjoy it.