Donald Trump is leading the GOP field in polls of Republican voters. This fact has some grabbing the popcorn, others tearing out their hair, and still others shaking their heads at the state of U.S. politics today. But if you're among the one in four adults in the US with a mental health condition, if you have an interest in children's health, or if you love an autistic person, then you might view Trump as more troubling than bemusing or amusing.

First, there's his willingness to apply mental illness as an epithet. Using Twitter TWTR -3.64%, his favorite online tool, he has called into question Obama's mental health, calling the president's decision not to block flights from West Africa during the 2014 Ebola scare "psycho." He doubled down on those comments later, stating in an interview that "there's something wrong" with Obama, implying that the POTUS just isn't quite right in head because his policies don't align with The Donald's. Of course, that scare ended without realization of the fears that motivated Trump's outburst.

Trump also appears to believe that mental illness, rather than guns or other deadly weapons, kills people, saying about the Louisiana movie theater killings:

Well, these are sick people.  I mean, these are very, very sick people.  This has nothing to do with guns.  This has to do with the mentality of these people.

And then there's his belief about autism. Eight years ago, Trump was evidently convinced that vaccines cause autism—or at least, vaccines as administered according to the recommended schedule. He decided in 2007, he said at the time, to have his son administered "one shot at a time" in what he described as "a very slow process." He also said that his "theory is the shots" are responsible for autism.