“…Efforts have been made to describe characteristics of those who attend, their length or degree of participation and involvement, changes in their behavior, their substance use outcomes, and their perceived usefulness of the groups (see, for example, Connors & Dermen 1996;McCrady, Epstein & Hirsch 1996;Morgenstern et al 1996a;Morgenstern et al 1996b;Burton & Williamson 1995;Montgomery, Miller & Tonigan 1995;Carlson, Dilts & Radcliff 1994;Kaskutas 1994;Snow, Prochaska & Rossi 1994;Emrick et al 1993;Humphreys & Woods 1993;Emrick 1989Emrick , 1987Ogbome & Glaser 1981;Boscarino 1980;Trice & Roman 1970;Trice 1957).…”