Does a diagnosis of depression automatically ground a commercial airline pilot?
An Air Transport Pilot (ATP) requires a 1st class medical certificate in order to fly in that capacity. Major depression and the associated medications used to treat it are temporarily disqualifying but not necessarily permanently. There is now a waiver process that may allow an airline pilot to continue flying even while taking some antidepressants once they are shown to be stable. However, it isn’t automatic or guaranteed in any case.
Here is what the FAA has to say about it:
https://www.caa.co.uk/WorkArea/DownloadAsset.aspx?id=4294973468
The above is a flow chart for CAA authorisation (i.e. UK Civil Aviation). Based on that it would seem that provided you have recovered from the illness for a period of time then you can be allowed to fly.
The above is a guide from the FAA. See the section “Bereavement; Dysthymic; or Minor Depression”. Again it appears that successfully treated depression is not a barrier to holding a medical.
On the other hand the initial diagnosis would ground the pilot. But it’s not a career ending illness.
Edit: What Shagnasty said.