I was 63 when diagnosed by a competent professional. I'd been going to my local Mental Health Center for years, for Clinical Depression, and on antidepressants. My daughter heard about Asperger's in a college Counseling course (the idea being Church Employee Counseling, a Christian college) and said "That's my Mom!", but the Center didn't have anyone qualified to do the professional diagnosis: but she did tell them about it. Then the Center got an inquiry from a PhD Psychologist specializing in Autism, working at the Children's Hospital 50 miles away, who was writing a paper about people who'd lived a life undiagnosed, and how they'd coped with life. Of course, the kicker was _finding_ undiagnosed people to study!
So we went over there, she did my diagnosis and her interview.
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Asperges me, Domine