Like I said, you didn't read the article or you would've seen that it was an incredibly small case study and that the data was inconclusive and not indicative of large-scale results. They even admit to outliers where grey matter increased and there were inconsistencies between heavy and light users. Almost every study in the last 10 years has been about adolescent use that leads to heavy adult use. Those studies show that in heavy, long-term usage there is a slight decrease in IQ (less than 10 points) and memory. That doesn't reflect recreational or light usage, and it doesn't reflect medical usage. Cigarettes and alcohol are also much worse when you start young and use heavily into adulthood. It doesn't mean everyone that smokes or drinks in any capacity is at the same risk. Marijuana is FAR less addictive than nicotine, and FAR less debilitating than other drugs including alcohol. Of course heavy usage has side effects, but there is no study in the last 10 years that agrees with you that it is dangerous or addictive like other drugs. If you overuse, then of course you can create an addiction, but the same can be said for sugar.
You need to actually read some scientific studies if you want to try and use science to prove your point.