If 2 clinical experts, 3 psychiatrists and dozens of psychologists didn't think you had ADHD, but eventually one person did, how do you know with certainty you actually have it?
It's not that they didn't think I had it. It never occurred to them that it might be the problem, for several reasons. I presented very clearly suffering from MDD and general anxiety and have been medicated for that my entire adult life. But in fact the MDD and anxiety were just symptoms of living undiagnosed and trying to live as best I could with what worked for me.
> comments such as this can be incredibly harmful
For anyone reading this exchange, ignoring, or going against, the opinion of 30+ mental health professionals can also potentially be harmful.
In defense of GP, I want to caveat with this: if you go to a random psychiatrist and tell them about your issues, it's quite likely you'll get evaluated for the "usual suspects", such as depression. A proper evaluation (not just initial diagnosis, but matching treatment and noticing effects) can easily take over a year, since medication used in depression treatment usually take a month to kick in, and you might need to go through several before finding one that works for you, if at all - while also dealing with some nasty side effects.
Now, imagine a person with ADHD staring this path. How likely is it they'll go through the process diligently for a year or more, until the doctor figures out something else is going on? What's more likely to happen is, the person will keep taking the meds for a while, then forget to schedule a visit before running out, run out, enter withdrawal, then be unable to schedule a visit, leave withdrawal few weeks later, and feel too ashamed to talk to that doctor again. So in a few months or more, they may go to another psychiatrist...
... who will want to re-examine them for depression just to be sure, starting the cycle anew.
I wasted a decade of my life on exactly this.
Hence my standing recommendation: if you suspect ADHD, find a psychiatrist who's actually specializing in adult ADHD (and not just has it on a list of things they can help you with). ADHD can often be diagnosed or ruled out in days to weeks; going to an ADHD specialist isn't about trying to "get your favored diagnosis" (if you feel worried about this, just be up-front with them) - it's about minimizing the chance they'll dismiss this as an option, as (from copious anecdotal evidence) most other psychiatrists do.