How long does Prednisone hair loss/thinning last?

My partner has been on some pretty high doses (like 50mg) of prednisone for a while and is currently on an extremely slow tapper (going down 5mg every 2 weeks). Throughout his time on prednisone he’s experienced pretty noticeable hair thinning/hair loss and as a cancer patient who already lost his hair once to chemo, it’s really been bumming him out (and the mood swings from the prednisone sure isn’t helping with this either).

So I was wondering: if you experienced hair thinning, how long after tapering off of prednisone did it take for your hair to start growing back?

I’m just trying to get an idea of a timeline in hopes of cheering him up a bit~