Table 2

Description of included studies

VariableTotal—n (%)Excluding discussion forums—n (%)
Total—N28495
Continent of corresponding author
 Asia12 (4.2)5 (5.3)
 Australia14 (4.9)3 (3.2)
 Europe78 (27.5)19 (20.0)
 North America179 (63.0)67 (70.5)
 Not reported1 (0.4)1 (1.1)
Study start date—median (range)2006 (1997–2011)2008 (2000–2011)
Study duration—median (range)5 months (1–117)3 months (1–117)
Sample size—median (range)124 (1–16703)*130 (2–16703)*
Publication type
 Journal article255 (89.8)75 (79.0)
 Abstract15 (5.3)8 (8.4)
 Dissertation14 (4.9)12 (12.6)
Study design
 Quantitative
 Randomised controlled trial48 (16.9)6 (6.3)
 Non-randomised controlled trial6 (2.1)1 (1.1)
 Controlled before-after1 (0.4)
 Observational11 (3.9)3 (3.2)
 Cross-sectional63 (22.2)33 (34.7)
Qualitative
 Case study1 (0.4)
 Case series3 (1.1)2 (2.1)
 Ethnography3 (1.1)2 (2.1)
 Grounded theory6 (2.1)2 (2.1)
 Phenomenology6 (2.1)1 (1.1)
 Qualitative (other/not specified)46 (16.2)16 (16.8)
 Mixed methods33 (11.6)9 (9.5)
Other
 Content analysis57 (20.1)20 (21.1)
Authors’ conclusions
 Positive186 (65.5)56 (59.0)
 Neutral65 (22.9)23 (24.2)
 Negative15 (5.3)10 (10.5)
 Indeterminate18 (6.3)6 (6.3)
  • *Excluding one study that examined >3 000 000 tweets.