Interesting. In 2003 I read a book called "ADHD in adults" by Weiss. There was one character there that was near identical to myself and so I pusued a psychiatrist specialising in ADHD, one of two in Melbourne. He subsequently diagnosed me with the illness, then later depression.
For 6 years I took various medications for ADHD none of which worked. I then got a second opinion from a psychiatrist and a second psychiatrist that sat in on my interview over his lunch break. Their combined diagnosis - Bipolar 2, depression and dysthymia with some lingering anxiety. I was put on the appropriate meds and presto- was and am much better and stable as bipolar can be.
It was the mania that mirrored ADHD symptoms.
So the message is clear- get a proper diagnosis before assuming. And a second opinion if you can.
All the best.