RE:  Increased risk of testicular cancer, mental illness...

You may be another one who needs to read some of the numerous studies conducted over the years by reputable universities and scientists.  
"Does marijuana cause cancer?. Dr. Sean McAllister of the Pacific Medical Center in San Francisco has spent years researching cannabidiol.....   “Cannabidiol offers hope of a non-toxic therapy that could treat aggressive forms of cancer without any of the painful side effects of chemotherapy”

The US government solicited a study in 2015 - The research, conducted by a team of scientists at St. George’s University of London  found the two most common cannabinoids in marijuana, tetrahydrocannabinol (THC) and cannabidiol (CBD), weakened the ferocity of cancer cells.... recent studies confirm cannibis can reduce certain types of cancer cells and totally kill others."

As for mental illness, it's been shown to drastically reduce symptoms of anxiety.

Please read some science-based studies.