Yuuuup!
I was diagnosed when I was 42 and it literally changed my life.
Like Nome, my depression went away. My diagnosis armed me with the knowledge of what was happening and along with a good therapist I was able to recognize and break the cycle of ADHD burnout.
I am truly happy now.
A thread I'm transferring over, answering a question asking me how I was doing after a few years medicated for ADHD - how my comorbid conditions (depression, anxiety) were doing, how the medication was working.
I answered there, but here it is again:
My depression is functionally gone.