Three pieces of statistical good news:
First, from the New York Times, several serious diseases are getting less common, and we don’t really know why. Heart disease rates have been falling for my whole lifetime. More recently, rates of dementia have been going down (though the number of cases is going up, because there are more old people). Hip fractures are down. And now colon cancer is getting less common. In all these cases there are well-understood contributing factors, but these aren’t enough to explain the decrease (except perhaps for heart disease).
Violence is also down: in the specific politically-relevant case, fewer US police officers have been shot during the Obama presidency than the equivalent periods of Clinton, Bush, or Reagan.
And finally, in US states where medical marijuana has been legalised, there are fewer prescriptions written for other competing drugs. (Washington Post, original research paper). This is most dramatic in prescriptions for painkillers: marijuana is competing successfully against opioid narcotics.