Autism and ADHD are not just one set of characteristics, but it is a spectrum of a variety of characteristics. Each autistic person has a different set of these general characteristics, and they are each applied uniquely to each autistic person. So you can't just find a "definition" of autism and apply it to yourself to see if you fit or not.
For instance, a common characteristic of an autistic or ADHD person is "stims" or repeated actions that we do in order to balance our overwhelming energies. But each autistic person has a different stim or set of stims we use. Stereotypically, an autistic person might flap their hands, bounce their torso, or pace manically. My stims are that I bounce my leg, pace when talking, fingerspell (sign language) words I see or randomly think of, or sing aloud. All of these can calm me down and get me ready for another activity.
The fingerspelling, especially, is rare as a stim. Very few people do that, but when we think of it as a form of echolalia (repeating a word one hears or thinks of), then it is not uncommon among autistic folks, it's just that my version is quieter. Singing is pretty rare, but humming is pretty common..
Another thing about stims is that we can sometimes exchange one stim for another. For instance, I will scratch my leg, often until I'm bleeding. That is not a positive stim. But I found that there is a group of "toys" called fidget toys that are made especially for "pain stims". A "pain stim" is when we are so agitated that we need pain to break us out of the funk we are in. I got a "cutie pie" fidget toy, which is a cylinder for one's palm and it has sharp, scratchy surface so I can have pain stim need be "scratched" so to speak, if I roll it in my hands. That's not for everyone, but it works for me.
Stimming is just one characteristic on the neurodivergent spectrum, and you see how complicated it is? So there are a number of other characteristics. Some examples:
Inability to be "socially acceptable"
For example, I have a struggle answering the basic question "how are you?" I overthink it and can't decide what they want to hear without me needing to lie. "Fine" is a lie, by the way.
Difficulty communicating
I have periods of time in which I will have difficulty talking or initiating conversation.
Hyper- or hypo activity
I will have times, sometimes months, in which any activity is difficult to do without a meltdown.
Sleep difficulties
I will often wake up in the middle of the night, unable to sleep for an hour or two.
BM or urination problems
I feel that I need to go to the bathroom, but I cannot release my waste (this is usually due to anxiety)
Depression/anxiety
I have constant depression, daily. I have frequent anxiety but for years I denied it.
Seeking dopamine raising activities
I would volunteer for difficult activities, without fear or dread.
Hyperfixation on a subject that could last weeks or almost all of one's life
As soon as I heard about Jesus (before I was a Christian), I would seek more and more information about this person. On the other hand, I went through a number of months where I needed to find out information about the cartoon Steven Universe.
Inattention on what is "important" or hyperfocus on what is "unimportant"
If I am having an important conversation in a living room, it is difficult for me to not pay closer attention to the books on a shelf than the conversation I am supposed to have.
Meltdowns or shutdowns
I can get so emotionally distraught that I can't talk or have to walk away or I will get very upset and start yelling.
Executive dysfunction
I need to make a phone call but I can't bring myself to do it. That part of my brain just isn't accessible.
Any one of these characteristics any "normal" person (neurotypical) can have. An autistic/ADHD person will have many of them (probably not all) and they are continuously a hindrance to achieving personal goals or in having relationships with others. And when one experiences these over a long period of time without a sufficient break, then comes burnout. Personally, for the last few years, I've been in perpetual burnout.
I don't say this for people to have pity on me or other autistic/ADHD folks. Just so that we can understand each other and give each other space when necessary.
