Let me answer that. As Dr. Courchesne said, because of the war on drugs, principally in the U.S., for a very long time it was very hard to get funding to do research. However, there is research available. As she also said, most of it shows the harms associated with cannabis use.
There is actually very little good research showing any positive health effects for the use of cannabis, even though you will see in the popular press that people who tend to use cannabis will talk about how profoundly it has helped them. In fact, the research that is out there, including both reviews and reviews of the research out there on health effects, show overwhelmingly that there are negative effects, certainly on mental health and on physical health as well.