TABLE 3. Results of included systematic reviews.

Citation	Desirable outcomes	Harms or limitations	Usage, reach engagement	Conclusions of the review
Chang et al., 20129	• Inconsistent effect on BMI and weight; concluded that few studies quantified effect • Inconsistent effect on physical activity levels (2 positive, 3 negative)	• Use of social media was low (25%), and 85% of studies used researcher-developed platforms that may not be as user-friendly and vibrant and connected to large community of users • Use of social media for weight management may reduce positive feelings associated with social media use	25% of users reported using social media sites	“We found that social media is being incorporated in online weight-management interventions largely through message boards and chat rooms with unclear benefits.”
Eysenbach et al., 200434	• Weight loss or healthy body weight: mixed but mostly nonsignificant results • Behaviour change: Of the 6 studies that looked at this outcome, abstinence rates were higher with peer support in 1, study and similar in the group with full psychoeducational intervention • Only 3 studies out of 12 looking at depression and social support reported an improvement • Effects for social support measures were mixed: some indicating significant effects and others not • 5 studies looked at glycosylated hemoglobin and only 1 showed significant improvement • Of the 3 studies of health care utilization, 1 reported a significant decrease, 2 reported increase in phone calls to providers	No adverse effects reported. The authors saw little commercial or professional interest in evaluating pure virtual communities. Studies investigating “natural” self-help are difficult to recreate in controlled setting as participants may have an intrinsic desire to participate in virtual communities and general recruitment may not capture the right population	Some studies found virtual community component not heavily used	“In view of the wide variation in interventions, measurement tools, and populations studied, and the lack of methodological rigour in the majority of studies reviewed, the effect of online support groups on health-related outcomes and health care resource use remains unclear.”
Griffiths 200939	• 3 of 4 multicomponent trials reported a reduction in symptoms of depression while 1 found no effect • The non-experimental studies had mixed findings • Multicomponent studies were significantly less likely to yield positive outcomes than stand-alone interventions • Outcome was not affected by the use of synchronous (chat room) compared to asynchronous (bulletin board, listserv/newsgroups) Internet support groups, whether or not the study reported using a moderator or whether the board was public, research and/or restricted access	No adverse effects reported	Not reported	“There is a need for high-quality research to investigate the effect of [Internet support groups] on depression outcomes.”
Hong et al., 201235	• Most studies reported positive effects of online support but none of the RCTs reported significant positive outcomes, e.g. no positive improvement in mood, adjustment to cancer, self-related health status, health-related QOL • 1 of the 4 RCTs reported improvements in emotional well-being but results for psychological well-being were mixed (1 study reported improvements while 1 reported more psychological distress in the intervention group)	1 study reported more psychological distress in the intervention group.The studies didn't include online cancer support resources such as Facebook. Limited number of studies	Not reported	“Preliminary but inconclusive evidence of positive outcomes”
Lai et al., 201431	No quantitative measure of benefits on suicidal ideation; 2 papers reported positive feedback from users who were in crisis	• Risk of low-quality information (only half evidence-based), possible breaches of confidentiality, and limits to access may not match cultural background of user • Risk of non-genuine messages (< 5% in one online support group) • Risk of “flaming” effect of hostile comments • Risk of Internet addiction, limited to literate clients • Possible safety concerns in acute crises	Not described	“Preliminary evidence that suggests the probable benefit of web-based strategies in suicide prevention”
Medina et al., 2013 32	Mutual support, support seeking as self-help, support given as stored currency, moderating information, dilemma of sharing, support as bad debt, reduced medical visits, reduced isolation, improved QOL (qualitative data/themes), and increased hope	• Dissatisfaction or frustration of not finding what they wanted • Risk for socially sensitive people, risk of lack of moderation of content, risk of unreliable data	Not described	“Online support groups are a large repository of quality information related to general and specific diseases, such as cardiovascular diseases, and an appropriate environment to foster or create a support community between participants.”
Moorhead et al., 2013 8	• Increased interactions with others • More available, shared and tailored information • Increased accessibility and widening access to health information • Peer/social/emotional support • Public health surveillance • Potential to influence health policy	No adverse effects reported. Limitations included poor reliability, quality concerns, lack of privacy, unaware of risks of disclosure, harmful or incorrect advice, information overload, not sure how to apply information to personal situation, some media more effective for behaviour change, adverse health, negative health behaviours, deter people from visiting their health professionals	Not described, but some disparities in use need further investigation (e.g. more female users). Helpful as social/emotional support, particularly with connections where ties are strong, peer-to-peer interaction, one-sided/imbalance for professionals in professional-to-patient interactions needs to be managed, reliability/quality of social media is unregulated	“Although there are benefits to using social media for health communication, the information needs to be monitored for quality and reliability, and the users’ confidentiality and privacy need to be maintained”
Nef et al., 201333	Main benefit was knowing what was going on in younger family members' lives	No mental health harms identified nor increases in loneliness. Barriers described were lack of privacy; did not understand purpose of social media sites, technology was not user-friendly	Described as low acceptance and use	“Social networking sites have the potential to support today’s and tomorrow’s communication between older and younger family members”
Newton & Ciliska, 200612	No difference in effect for eating disorder inventory or eating disorder examination questionnaire	None reported but the authors mention that an ethical concern for Internet-based interventions is the inability to detect and address serious eating disorder symptoms that could be detected in a face-to-face encounter	Completion in the intervention group ranged from 77%–92%	“No conclusive statements can be made regarding the impact of Internet prevention programs.”
Nieto 200840	The results were not aggregated. Both studies found positive results	No adverse effects reported	Not reported	“In general the results of the studies reviewed demonstrate that treatments based on new technologies are effective and efficient and that patients hold positive attitudes toward them.”
Williams et al., 2014 30	Weight not statistically significantly different in 10 studies: SMD 0.00 (95% CI: −0.19 to 0.19). Levels of physical activity not statistically significantly different: SMD 0.13 (95% CI: −0.04 to 0.30), 12 studies	No adverse effects reported (but high dropout rate from intervention group). The authors reported some risks of confidentiality, cultural differences, hostile comments, fake messages, safety concerns in crises	23% of intervention group completed the study	“Despite its growing popularity, there is little evidence that social media interventions demonstrate a significant benefit for improving healthy diet and exercise.”

Abbreviations: BMI, body mass index; CBA, controlled before–after study; CI, confidence interval; QOL, quality of life; RCT, randomized controlled trial; SMD, standardized mean difference.