Autism rates are increasing for several reasons.
1. Kids who were counted as retarded 50 years ago are now more often called autistic instead.
2. Shy and socially awkward kids are getting classified as autism spectrum, not just the head bangers, so the numbers go up. It is like calling people with thick glasses as being on the blindness spectrum.
3. Autism as a mental disorder does go up when the mother takes antidepressants during pregnancy. More use of the mood altering drugs means more kids whose brains are affected by prenatal exposure to those drugs.