I can think of a handful of people that I have known that have killed themselves. My brother's best friend did it 25 years ago, my best friend's brother did it about 10 years ago. I have also had a couple of high school classmates that have taken their lives. Everyone other than the brother of my friend was (I presume), neurotypical. My friend's brother had some mental illness and addiction issues going on at the time.
Probably the most significant suicide in my life was when my best friend from my time in college made the decision to end his life a little less than two years ago. He struggled with schizophrenia most of his adult life, and was in a psychotic episode when he passed. Probably one of the brightest and most cultured persons that I knew. He was on the staff at the college that I went to, so we would spend a lot of time together there. We also were active in the same church, and in politics and civic affairs. He always wanted to do more with me, I feel bad that I didn't spend more time outside of these venues. When he had his psychotic break, he disappeared from the world. Even though I regularly saw a family member, there was very little conversation about how he was doing in the year he disappeared to his suicide. Sadly, in the grief of this situation, I ruminate and obsess over the friendship and his death. The latest obsession has been trying to find someone to replace him, which I have yet to do. 