I think this is the first explanation that makes sense.
I've always been "different" and never knew why. My parents were frustrated and tried lots of different approaches and consulted with different doctors of various types. My teachers pretty much hated me. I was always treated like I refused to apply myself, and when I was found to be of high intelligence it only made the adults in my life more confused and frustrated.
As an adult, I have been to a few different counselors. I have been diagnosed with adult ADHD, dysthymia, cyclothymia, and social anxiety disorder by various mental health professionals. I have learned to cope with many of the problems and "eccentricities" that I have but I'm still under a lot of stress because of it and I have been searching for answers.
I've always been extremely ticklish to the point of it being a real issue, which is embarrassing when you're a 6'4 man. I also can't stand when people talk towards my ear, as in when I'm looking forward and they are facing me. Similarly, when people strongly enunciate certain consonants it bothers me so much it makes my skin crawl and my muscles tense. These are the symptoms that are ignored by all of my other diagnoses that The counselors and doctors and psychologists have always seemed more focused on why I couldn't concentrate at school or why I was irritable and didn't fit in or have friends.
I wish some authority figure in my life had known about SPD 20 or so years ago. I could be so much better off right now than I am.