I have looked online for studies, and have found very little. My son was diagnosed with dysthymia (low-grade depression) when he was 16, and diagnosed with high-functioning autism when he was 17. He was treated for the depression off and on for a few years, but often didn't take medicine - he didn't like pills. Drew was extremely bright, scored very well on standardized tests, was living in an apartment and working while attending college. However, he was bullied since he was very young, had a speech and language delay when he was a toddler, and had started having trouble relating to his peers in mid- to later elementary school years. He finally found a girlfriend, but after they broke up earlier this year, he died by suicide.
I do know that people on the autism spectrum have a higher incidence of depression than the general population, and I now know that people with suicide have a very, very high percentage of previously being diagnosed with depression. Although there is no study that we know of that links autism with suicide, it seems safe to say that there is a relationship.
I hope you all will watch for symptoms, such as sleep disorders, headaches, lack of enjoyment, changes in relationships, striking changes in mood, lack of appetite, and any others that may set off an alarm. Please ask for help from someone you trust. We need all of you in our world. We each have an important part to play in each other's lives. Drew's loss has devastated so many people. He had many friends who cared about him. So what if they were often several or more years older than his peers? He was a quirkly, difficult, thoughtful, brilliant person. We miss him terribly. We now have some idea of how much pain he was in from the depression, for many years. Please do not put your families and friends through this. Help them help you!