For posterity's sake, the subject of my PM to him was "Suicide Prevention Hotlines", and the body was as follows:
Hi. I'm a member of the staff at the SCP Foundation wiki, and your recent application greatly concerned me. I've personally been struggling with suicidal ideations since I was a small child, and I know how scary it is to feel like you're alone in the world. I was able to find two suicide prevention hotlines in Sweden. Please call one before you do anything drastic. They can help you.
Nagon att tala med Samaritans
GOTHENBURG
Contact by: - Phone
Helpline 1: (46) (0) 31 711 24 00
Helpline 2: (46) (0) 31 711 24 22
Website: www.natm.se
Opening hours:
Mon, Tues, Wed, Thurs, Fri: 18:00 - 22:00
Nationella Hjälplinjen
Box 22335
104 22
Stockholm
Contact by: - Phone
Helpline 1: 020 22 00 60
Helpline 2: Textphone: 020-22 00 70
Website: www.nationellahjalplinjen.se
Opening hours:
Mon, Tues, Wed, Thurs: 13:00 - 22:00
Fri, Sat, Sun: 13:00 - 23:00
(I've been lucky enough that my symptoms are currently very well-suppressed by medication, but I'm not a doctor, and I don't know his situation, so I decided to err on the side of "let the professionals handle telling him about medication".)