Not really. The coincidence of steadily decreasing drug laws and the explosion of gun control is too obvious for the attentive to miss. As drug use goes up, gun violence goes up and increased gun control occurs.
From Patrick Purdy in Stockton, California, to Thomas Hamilton in Dunblane, Scotland, the one common denominator is a long known history of mental illness. That marijuana causes increased psychotic episodes, in the known mentally ill, is also another common precursor to violence.
I'm willing to bet you a $1,000.00 that those who have gone "postal" have used pot, or another illegal drug, or stopped their legal "meds", at least 72 hours before they started shooting people.
The bet thing is a real non starter on-line.
Not to mention the research you have to do to prove your dubious point.
Please provide evidence that drug use has gone up.
What decreasing drug laws? At the beginning of the 20th century, you could legally buy cocaine, in your Coke-a-Cola no less, smoke whatever you wished, and you could also own whatever firearm you chose without any federal permission. It's not just a coincidence that the first federal firearm law was patterned after the Harrison Narcotics Act. Very explicitly so in fact according to the testimony of the Attorney General before Congress when the NFA was being debated and passed. Both laws used, illegitimately IMHO, the delegated power to tax to regulate what was otherwise not within the delegated powers of the federal government to regulate and in the case of the National Firearms Act, to infringe upon that which the Constitution states "shall not be infringed".
It's also probably no coincidence that these laws were passed shortly after the repeal of alcohol prohibition.