I can speak from recent experience on this.
If you are either being treated for depression (however it is worded by your GP / consultant) or taking anti-depressants, then you must inform the CAA aeromedical people with all the relevant details and stop flying if directed to do so.
They require a period of 2 months after stopping the medication (SSRI / SNRI) before you can be considered fit to fly again. I can vouch for the fact that ceasing SSRIs can be an absolute ba5tard. They may require you to meet with a CAA AME before re-instating your medical certificate.
I didn't need to, but it was for a class 2 and I had a letter from my consultant that gave chapter and verse, plus a glowing endorsement of my "fitness to fly". I now have my class 2 back (almost 4 years after losing it), and I will be flying again before the end of the year.
Good luck - I hope this is just a brief setback for you.
SD