Table 1.

Summary of studies—Study type, participants, and recruitment.

Authors (year)	Study type	N	Participant eligibility	Method of recruitment	Recruitment duration	Recruitment costs
Batterham (2014)	Systematic Investigation	1893	Australian, ˃18 years old	Facebook advertising: First period—4 ads with direct link (2x2 factorial design- “problem” vs “positive” terminology and “altruistic” vs “self-gain” terminology). Second period- Facebook page that you “liked” and page showed visible links to the survey site. Facebook compared to previously completed study which used postal and telephone surveys.	First period recruited for 1 month. Second period recruited for 2 months.	Direct link cost $9.82 per completed survey. Survey linked to the Facebook page cost $1.51 per completed survey.
Fenner (2012)	Exploratory study	278	Female, 16-25, live in Victoria, Australia, willing to complete health survey	Facebook advertising	4 months	Cost-per-click: $0.67. Cost-per-participant: $20.14
Frandsen, Walters, & Ferguson (2013)	Multisite randomized trial	266	Older than 18, smoke more than 10 cigarettes a day for the last 3 years at least, not enrolled in another smoking cessation trial in the last 3 months, highly motivated to quit (>75 on 100 pt scale)	Two methods: Traditional—flyers, newspaper ads Online—Facebook ads	18 months	Average cost-per-click was AUD $0.95. Cost-per-participant was AUD $42.34. Newspaper cost-per-participant was AUD $21.52
Graham, Bock, Cobb, Niaura, & Abrams (2006)	Randomized controlled trial	764	Older than 18, smoking 5 or more cigarettes a day, no prior QuitNet.com use	Major search engines (AOL, MSN, Yahoo, Google), using an active user-intercept protocol	At least 7 months (recruitment was ongoing at published time)	[Not reported]
Graham, Milner, Saul, & Pfaff (2008)	Comparison of different media campaigns	9,655	Not reported	Two methods: Traditional—billboards, TV, radio, direct mail, physician detailing Online—national websites (banner ads), local websites (banner ads), paid search ads (per click basis)	One 6-month period, one 3-month period	First phase: $35 per participant (with a 9% conversion rate). Second phase: $38 per participant (with a 7% conversion rate)
Heffner, Wyszynski Comstock, Mercer, & Bricker (2013)	Pilot study	222	Older than 18 years, smoked at least five cigarettes daily for the past year, want to quit in the next 30 days, willing to be randomly assigned to either group, lives in the United States, has weekly access to the Internet, English literate, not participating in other smoking cessation interventions, and never used Smokefree.gov website	Two methods: Traditional—Standard media (news coverage on TV, radio, newspaper ads), emails, word of mouth. News coverage on online—medical Internet media, Google AdWords, Facebook advertising and free posts Twitter posts	10 weeks	Total cost: $9,429.83; Direct cost from Facebook: $1,250; Direct cost from Google: $3,320.53; Direct cost from press releases: $1,250; Cost-per-participant: $42.48.
Morgan, Jorm, & Mackinson (2013)	Randomized controlled trial	1326	˃18 years, from Australia, New Zealand, UK, Ireland, Canada, or US, access to Internet once a week, not getting help for depression already	Search engine advertising, Facebook ads, Forum posts, posts on relevant websites and online newsletters	14 months	Google keyword costs: Cost-per-click=AUD $0.09, cost-per-participant=AUD $10.75 (click-through rate of 6%); Google display network advertising: Cost-per-click= AUD$0.13, cost-per-person= AUD$14.71; Facebook costs: Cost-per-click=AUD $0.62, cost-per-participant=AUD $19.89 (click-through rate of 0.05%)
Ramo, Hall, & Prochaska (2010)	Comparison of three recruitment methods	201	18-25 years of age, English literate, smoked at least one cigarette in past 30 days	craigslist, Internet ads through Adbrite (2 banner ads and 1 text ad), email invitations	6 months	craigslist: Free to post (estimated $0.66 per participant for time spent); Adbrite: Cost-per-participant=$20.86 (Charge every 1000 impression); SSI (online sampling service)=$19.24 per completed survey
Ramo & Prochaska (2012)	Investigation of Facebook as a recruitment mechanism	1548	18-25 years of age, live in the United States, English literate, smoke at least one cigarette in the past 30 days	Facebook’s Ad program	13 months	Cost-per-click: $0.45; cost-per-completed survey: $4.28; Overall cost: $6,628.24
Ramo, Rodriguez, Chavez, Sommer, & Prochaska (2014)	Investigation of recruitment campaigns	79	18-25 years of age, English literate, go on Facebook 4 or more days a week, smoked 100 or more cigarettes in their lives, currently smoke one per day on 3 or more days of the week, access to camera required for bioconfirmation of nonsmoking.	Facebook’s Ads Manager program- Newsfeed ads and ads on the right column of the page	5 different standard ads, 2 sponsored stories, and 3 promoted posts were up for 3 weeks, 16 ads with a picture and text combination were posted for 7 weeks	Cost-per-click: $0.34; Overall cost: $2.024; Cost-per-participant: $8.80
Raviotta, Nowalk, Lin, Huang, & Zimmerman (2014)	Human Papillomavirus Vaccine Trial	220	18-25 years of age, male, fewer than five lifetime sexual partners, no history of HPV infection or vaccination, no autoimmune disease nor immunosuppression, no hospitalization in past year, no receipt of blood products or immunoglobulins within 90 days, no participation in other drug studies within 30 days, and no receipt of other vaccines within 8 days.	Two methods: Traditional—flyers, email, student newspaper ads, class announcements Online—Facebook ads	One 3-month period, one 5-month period	Facebook: Direct costs= $4,820, Cost-per-click= $1.24, cost-per-person= $110. Print ads and Flyers: Direct costs= $6,758, Cost-per-participant= $61
Valdez, Guterbock, Thompson, Reilly, Menefee, Bennici, Williams, & Rexrode (2014)	Feasibility trial	87	Study 1: 18 years or older, identify as Filipino, live in the United States; Study 2: 18 years or older, US citizen, diagnosed with type 2 diabetes, Facebook user	Already-established Facebook group	Study 1: 5 months; Study 2: 2 months	Study 1: No direct costs; Study 2: Direct cost= $118.17, cost-per-participant= $1.94