It took ~6 months for a diagnose (got diagnosed with depression by a shit psychiatrist that wouldn't consider anything else after 2 different antidepressants didn't work) and 6 years for a good therapy.

But my case is not usual, I had severe side effects for like half the stuff I took and other meds didn't work all that well. And it's hard to follow the treatment properly when you're severely depressed so that slowed everything even more. Only after ruling out a meds only treatment I could try alternate therapies, first electroshock which worked alright, I mean I stopped hating life, and then TMS which finally worked as it should. The latter was experimental at the time.

I hope yours is much faster, but I'm saying this so you do not get discouraged if it takes long.