Table 1 Detailed characteristics of included studies

Andersson et al., 2005 [47]

117

Mild to moderate

Treatment group: m = 36.4(11.5)

Control group: m = 36.3(9.9)

Internet-administered cognitive-behavioural self-help

Wait-list

Swiss

Berger 2011 [8]

76

Mild

Moderate

Severe

Dysthymic disorder

Total sample: m = 38.8(14.0)

Internet-based self-help program (Deprexis)

Wait-list

Swiss German

Choi et al., 2012 [48]

63

Major depressive episode

Total sample: m = 39.0(11.07)

Internet-delivered CBT program (The Brighten Your Mood Program)

Wait-list

Resident of Australia, but self-identified as of Chinese origin

Clarcke et al., 2005 [49]

255

Major depression

Treatment group: m = 44.5(10.5) Control group: m = 45.0(10.6)

CBT-based ODIN program

Treatment as usual

Not defined

Farrer et al., 2011 [50]

155

(relevant for us n = 80)

Mild and higher

Treatment group: m = 41.7(12.1) Control group: m = 43.7(12.3)

Web-based CBT (Web with tracking)

Not active control condition

Not defined

Gilbody et al., 2015 [46]

691

(relevant for us n = 452)

Moderate

Total sample: m = 39.86(12.65)

(1) Beating the Blues

(2) MoodGYM

Usual GP care

UK

Klein et al., 2016 [10]

1013

Mild to moderate

No means reported (participants were between 18 and 65 years of age)

Internet-program (Deprexis)

Care as usual alone

Not defined

Lambert et al. 2018 [60]

62

Moderate to severe

Treatment group: m = 39.3(12.0) Control group: m = 36.9(12.6)

Web-based course (eMotion)

Wait-list

UK

Mantani et al., 2017 [57]

164

(relevant for us n = 117)

Major

No means reported (participants were between 25 and 59 years of age)

Smartphone CBT program (Kokoro-App)

Switch alone arm (control arm)

Japanese

Mohr et al., 2013 [51]

102

(relevant for us n = 67)

Major depression

Treatment group: m = 47.6(12.4) Control group: m = 48.49(11.7)

MoodManager

Wait-list

African American; White; Other

Newby et al., 2013 [52]

109

Major

Total sample: m = 44.3(12.2)

Worrying and Sadness internet-program

Wait-list

Not defined

Newby et al., 2017 [58]

106

Moderate to severe

Total sample: m = 47.0(12.61)

Cartoon-style Web-based lessons teaching CBT skills

Treatment as usual

Not defined

Proudfoot et al., 2004 [53]

274

Mild

Moderate

Severe

Treatment group: m = 43.6(14.3) Control group: m = 43.4(13.7)

Beating the Blues

Treatment as usual

White; Bangladeshi;

Black African;

Black Caribbean;

Black other;

Indian;

Pakistani;

Other

Rosso et al., 2017 [5]

77

Major

Treatment group: m = 29.2(7.69) Control group: m = 28.8(6.74)

Internet-based sadness program

A monitored attention control group

Americans

Selmi et al., 1991 [54]

36

(relevant for us n = 24)

Major

Mainor

Intermittent

Total sample: m = 28.2(not reported)

Computer-administred treatment

Wait-list

All white

Smith et al., 2017 [59]

270

(relevant for us n = 129)

Major

Treatment group: m = 42.5(12.63) Control group: m = 37.59(13.29)

Internet-based sadness program

Wait-list

Not defined

Stiles-Shields et al. 2019 [61]

30

Moderate to severe

No means reported (participants were at least 18 years old)

(1) Boost Me (2) Thought Challenger

Wait-list

American

Titov et al., 2010 [55]

141

(relevant for us n = 94)

Major

Total sample: m = 43.0(12.86)

Internet-based sadness program

Delayed treatment group

Not defined

Van Straten et al., 2008 [56]

213

(relevant for us n = 81)

Major

No means reported (adults)

Web-based problem-solving program

Wait-list

Dutch

Total:

3954

(relevant for this meta-analysis n = 3226)

Mild to severe depression