I will send him to test it, but he is stubborn, continuing to take fermented foods and eat lots of vegetables in the hope of improvementA short, sharp course of cypro would possibly do wonders for him. It cleared up a longstanding rash I had on my shins and ankles, all but proving for me the deep connection between gut and skin. It should also help lift his mood. If he's never taken it, the standard advice: start super small, and build up to maybe 2-4 mg a day for a couple of weeks tops. If he gets drowsy, tell him that will pass after a few days and to up the coffee. If his day is too impacted by the 'zombie effect' of cypro, he can just try one small dose at night. Tell him not to be scared of it, since chemists dish out entire boxes of the stuff in 4mg tabs.
Ultimately though, I think working on gut health would be hugely beneficial for him. And find a kick **** therapist who knows about childhood stuff, the true cause of depression (no, it's ultimately not a metabolic issue as some folk round here would prefer to think). Depression is healthy in its own warped way - it's a siren song from the soul that something aint right and desperately needs attention. To take nothing away from the difficulty of it.
I wish him well .
PS also re SIBO - look into B1 (dig around on this forum for some amazing research), Haidut's camphor product and/or activated charcoal