My husband suffers from clinical depression, and OP didn't seem to help.
But what did help?
Liver flushing. It would send him into major Depression
the next day, but then by dinner time...whoosh...major high energy.
It is said that the liver is the organ that holds all your emotions.
OPing does cause some activity in the liver...so why not? If anything you should do it for dental health.
Also exercise. Those natural endorphins did wonders for him. But it's hard to say because he was dealing with a very severe disability of which we will probably always struggle with. I don't know if there is a "cure" out there for people with depression, but the best you can do is get them healthy. You are already working against the stress of their problem doing havoc to their body.
Since you are musing about this, look into acupressure massage and aromatherapy. I put a calming aromatherapy into our room and my husband got more and more depressed. Damn, it took me awhile to figure it out. As soon as I took that stuff out of the room he was better. It's that powerful! So I changed up the oil to Lavender only for awhile to clean out the air, and all was well again. Oils, when cold misted into a room, infuse into your lungs, and skin. It's not just an air freshener people!! And don't get me started on those Glade Plug-ins.......yikes....
If your friend is natural health friendly I would suggest a full course of cleanses, liver, colon, parasite......I remember when my husband and I got a high colonic, it was like he was floating on air for days. He said, and I quote "Well I finally got my Sh&t together". LOL.
He's been on Prozac. We've tried talk therapy. We've tried every damn natural health thing we could think of. Only one thing helped my spouse.
He found out he has Aspergers. That was about a year ago, and the man has not gone down the rabbit hole since. What a relief. As he will say, "Now I am validated and I now know why I'm such a freak".....I never thought of him as a freak, but he needed to know why he felt so different from other people. That was the big Kahuna of therapy. I think about all that time, and money, and useless therapy....! But sometimes these things happen.
Why the hell did I do such along post? Yikes, I'm sorry. Just couldn't stop typing I guess.