If you think the person has a serious addiction, then you could refer him to Narcotics Anonymous meetings (they accept anyone with any type of addiction).

You could print out these fliers and give it to him and say, "I know it's none of my business, but I'm worried about you." Print out http://www.na.org/ips/an/an-IP7.htm

You could find meetings and times and even bring him to a meeting. Find meeting here http://portaltools.na.org/portaltools/MeetingLoc/