Authors (published years)	Published years of included studies	Review method	Included participants	How interventions were categorised	Number of studies	Types of study included
Subjective social isolation interventions
Findlay [30]	1982–2002	Systematic review	Older people	(1) Increase social support (2) Psychoeducation/social skills training	17	RCTs, non-randomised comparison studies
Cattan et al. [32]	1970–2002	Systematic review	Older people	(1) Social skills training (2) Provide social support (3) Psychoeducation/social skills training	30	RCTs, non-randomised comparison studies
Dickens et al. [33]	1976–2009	Systematic review	Older people	(1) Increase social opportunities (2) Provide social support (3) Psychoeducation/social skills training (4) Address maladaptive social cognitions	32	RCTs, non-randomised comparison studies
Masi et al. [34]	1970–2009	Meta-analysis	Adults, adolescents and children	(1) Increase social opportunities (2) Provide social support (3) Address maladaptive social cognitions (4) Provide social skill trainings	50	RCTs, non-randomised comparison studies
Perese and Wolf [35]	Unclear	Narrative synthesis	People with mental health problems	Social network interventions: include support groups, psychosocial clubs, self-help groups, mutual help groups and volunteer groups	36	Unclear
Objective social isolation interventions
Newlin et al. [36]	Up to September 2014	Systematic Review and modified narrative synthesis	People with mental health problems	All types of psychosocial interventions	16	RCTs, non-randomised comparison studies and qualitative studies
Anderson et al. [37]	2008–2014	Systematic review	People with psychosis	All types of social network interventions	5	RCTs
Webber and Fendt-Newlin [38]	2002–2016	Narrative synthesis	People with mental health problems	Social participation interventions: include social skills training, supported community engagement, group-based community activities, employment interventions and peer support interventions	19	RCTs, non-randomised comparison studies, and qualitative studies