What causes autism: correlation vs. causation

In the 1960s it was thought that cold, unemotional refrigerator moms caused autism in their children. The theory was that these moms failed to give their children the emotional support that they needed to be normal. Few people nowadays think that parents' actions cause autism in children.

But as Valerie Paradiz writes, there may indeed be a correlation between unemotional moms and autistic children. Autism is a mostly genetic and so highly inheritable condition. So many mothers of autistic children have autistic traits themselves.

One common trait of autism is appearing emotionally cold to strangers. Consequently, researchers studying parents of autistic children might have reasonably concluded that many such parents are emotionally cold. These researchers erred, however, in confusing correlation with causation.