The big question for us is, do we consider the parts of our behavior caused by whatever we suffer from to be part of our identity or personality?
I do not now. I used to -- I had a fairly major crisis of identity after my diagnosis, because a very large chunk of what I considered to be my personality turned out to be ADHD symptoms. I literally had to refind myself.
But it turned out very well, because now I define myself based upon what my actual qualities are, rather than defining myself based on symptoms of a disorder. I no longer feel like everything about who I am changed after meds; I'm still the same person I was ten years ago, I'm just now more easily able to express that self without ADHD getting in the way.
Also, in almost all cases, the "new qualities" are better than the old ones. Whereas before, "I just can't finish things" was unfortunately something I considered to be part of me, now I am able to finish things mostly the same as neurotypical people. That leaves me free to define myself based on positive qualities -- good humor, optimism, and so on.
The thing is, it became much easier for me to feel okay about taking medicine when I realized that the goal of medicine is simply to bring me back to a "normal" level. I had been operating at a deficiency of certain neurotransmitters; the medication simply brings those levels closer to normal. Once I had adopted a more biochemical perspective on my brain and identity, my initial reluctance disappeared.
A side effect of this is that I kind of no longer believe personality is fixed. I really don't find that the things we tend to call 'personality' are the sort of permanent identifying landmarks to a person we want them to be. Now I've adopted a view that puts a much stronger emphasis on the actions a person chooses to take, which I think is a better way to identify a person's qualities anyways.
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I would hesitate though with ADHD in particular, because untreated ADHD reduces your lifespan in a statistically significant way, is literal hell to live through, and the treatments are perfectly safe and extremely effective. If someone has a child who is diagnosed with ADHD, I would beg them to not let their personal prejudices against medicine keep them from getting the child the help they need. As someone who lived through it as a kid, it was physically torture. The word "restlessness" sounds benign, but I find it to be quite similar to akathisia on bad days, which is really horrific.