Study	Reason for exclusion
Andersen 2000	RCT where the data relating to the peer support telephone component could not be extracted.
Anderson 2005	RCT where the data relating to the peer support telephone component could not be extracted.
Brindis 2005	Not an RCT.
Bullock 1995	RCT where there are trained volunteers ‐ no information about whether the volunteers were peers.
Carroll 2007	RCT where the data relating to the peer support telephone component could not be extracted.
Caulfield 1998	Not an RCT. Peer component not by telephone.
Chapman 2004	RCT where the data relating to the peer support telephone component could not be extracted.
Emmons 2005	RCT where the data relating to the peer support telephone component could not be extracted.
Gattellari 2005	RCT where peers are GPs (i.e. healthcare professionals).
Goodman 1990a	Not an RCT ‐ a randomised comparative trial.
Goodman 1990b	Not an RCT.
Gotay 2007	RCT where the data relating to the peer support telephone component could not be extracted.
Heckman 2002	Not an RCT. Not investigating efficacy of intervention ‐ report on prevalence rates.
Heckman 2006a	RCT where intervention facilitated by non‐peers.
Heckman 2006b	RCT where intervention facilitated by non‐peers.
Heiney 2003	RCT where intervention led by non‐peers.
Heisler 2005	Not an RCT.
Heller 1991	RCT where the data relating to the peer support telephone component could not be extracted.
Hunkeler 2000	RCT where the data relating to the peer support telephone component could not be extracted.
Ireys 1996	RCT where the data relating to the peer support telephone component could not be extracted.
Ireys 2001	RCT where the data relating to the peer support telephone component could not be extracted.
Keyserling 2002	RCT where the data relating to the peer support telephone component could not be extracted.
Krieger 2000	RCT where the data relating to the peer support telephone component could not be extracted.
Lando 1992	RCT where lay interventionists were used as opposed to ex‐smokers to provide intervention.
Mohr 2005	Not a RCT.
Mongeon 1995	RCT where the data relating to the peer support telephone component could not be extracted.
Ossip‐Klein 1991	Not an RCT. Trial where intervention is conducted by trained 'paraprofessional' counsellors.
Ossip‐Klein 1997	Not an RCT.
Park 2006	Not an RCT.
Preyde 2003	Not an RCT.
Pugh 2002	RCT where the data relating to the peer support telephone component could not be extracted.
Rene 1992	Not an RCT. Trained lay personnel not peers providing the intervention.
Ritchie 2000	Not an RCT.
Rudy 2001	Not an RCT.
Samuel‐Hodge 2006	RCT where intervention led by non‐peers.
Schwartz 1999a	Not an RCT.
Schwartz 1999b	Not an RCT and investigating impact of peer support on the provider.
Silver 1997	RCT where the data relating to the peer support telephone component could not be extracted.
Simoni 2007	RCT where the data relating to the peer support telephone component could not be extracted.
Solomon 2000a	Not an RCT.
Solomon 2000b	Not an RCT ‐ a randomised comparative trial.
Solomon 2005	Not an RCT ‐ a randomised comparative trial.
Stewart 2001	Not an RCT.
Stockdale 2000	RCT where the data relating to the peer support telephone component could not be extracted.
Sullivan‐Bolyai 2004	RCT where the data relating to the peer support telephone component could not be extracted.
Sutton 2006	Not an RCT ‐ before and after study.
Walker 2002	Not an RCT.
Weinberger 1989	RCT where intervention is education not peer support.
Wewers 2000	RCT where the data relating to the peer support telephone component could not be extracted.
Whittemore 2000	Qualitative study of peers ‐ not RCT.
Wiggins 2005	RCT where the data relating to the peer support telephone component could not be extracted.
Wolke 1994	Not an RCT.
Wong 2007	RCT where the data relating to the peer support telephone component could not be extracted.