In the wake of the mass shooting in Las Vegas on Monday, scientologist/actor Kirstie Alley tweeted that the "mystery of Why there were no 'shooters' or almost 0 before the 1980s" had to be solved. To that effect, she added that "mass usage of psychiatric drugs" was a "common denominator of 'shooters.'"
Alley pointed out that a certain percentage of psychiatric drugs have side effects of "VIOLENCE & SUICIDE." Of course, a great many people not on psychiatric drugs also experience and act out on violent and suicidal thoughts. In fact, they are often prescribed psychiatric drugs to help with those feelings.
When people on Twitter questioned her, Alley insisted that her idea was not a "theory" but a "statistic."
Scientologists are well known for their strong anti-prescription medication stance, preferring vitamins instead. Remember when Tom Cruise criticized Brooke Shields for saying that she took antidepressants after suffering postpartum depression, calling it "irresponsible"?
Interestingly enough, an article in the Washington Post from July 2016 points out that "[b]etween 1993 and 2013, total gun homicides were nearly cut in half, primarily during the 1990s. Over the same time period, violent crime as a whole went down by about 75 percent. The increases in fatalities we’ve seen [in 2016] don’t come close to reversing the trend."
Given that psychiatric drugs were prescribed a great deal in the 90s and aughts, combined with the fact that Las Vegas shooter Stephen Paddock is not reported to have been on any psychiatric drugs (as far as we know), it doesn't seem that Alley's statement holds much water.