I agree with whats been said above, advise him sure, but let him make up his own mind. Personally, i have suffered from depression in the past but also enjoy tripping either on shrooms or LCD. I'v never had a bad trip because i can understand my own thought patterns and know not to be trippin when i'm particulary stressed or anxious or down in the dumps bout sum sh*t, cuz it would intensify those feeling and would be sh*t craic. Acid and schrooms feed off ur own imagination so it could be the best you can possibly imagine or the worst, the choice is yours really... But ye there are a few things to help keep things on an even keel:
Setting: somewhere familiar, comfortable,
Company: Friends, people you know and trust
Weed: lots of it! Bongs, Hookah Pipes, Waterfalls, also pre-roll spliffs as it can be challanging with a head full of acid
Alcohol: something tasty, i love beer, whiskey Guinness or scotch but that's up to you
Music: chilled, relaxed, mad and crazy, regaaee always brings you back to earth, metal and mad heavy Dub Step can be pretty intense! you have been warned.
Activities: Anything to keep your mind busy, talk laugh, joke, doing something creative, If your a painter, paint, a musician, play! Where im from, County Down in the North of Ireland we like to trip mad with guitars, bongos, mandelins, bodhrans, tin whistles etc.
but that's us dude, your friend needs to find his groove.
Last but not least a trip around a park or a nature reserve or something like that is a must. Nature is perfection when tripping. Hope you'se have loads of fun btw. Am hitting the Dam myself for 4 days on Sunday for my 21st! Can't wait!!!!
Peace