A misdiagnosis and even the wrong medication is the worst to experience. Finally in my 33rd year of life (18 years since finding out about ADHD) I found a medication that helps my anxiety and depression which allows me to focus on the downsides of the ADHD.
This isn't an ad for mirtazipine. :)
Genuinely curious - do you in fact take mirtazipine to manage AD(H)D? I've never had it recommended as a treatment option.
I've tried a few other drugs for both ADHD and depression / anxiety over the years, but this one seems to be the sweet spot between helping with everything. Hardly scientific, but it's my experience.
I should note that at lower doses mirtazapine (remeron) helps with insomnia. For me, I'm on a higher dose (45mg) where this isn't the case.
While a psychiatrist can make the diagnosis, IME they're more likely to go after the secondary long-term effects as described above.