Table 4.

Pooled analysis of mindfulness intervention in improving loneliness.

Type of analysis (PICO)	Trials	Pooled Mean difference (95% CI)
Main Analysis: P: Varied characteristics (no known mental health conditions) I: Varied mindfulness interventions C: Wait-list O: UCLA-R scale	Creswell et al., 2012 Dodds et al., 2015 Mascaro et al., 2018	MD = −6.33 (−9.39, −3.26)* I2 = 0.0%, p = 0.688
Subgroup Analysis 1 (CBCT only): P: Varied characteristics (no known mental health conditions) I: CBT only~ C: Wait-list O: UCLA-R scale	Dodds et al., 2015 Mascaro et al., 2018	MD = −6.05 (−9.53, −2.58)* I2 = 0.0%, p = 0.425
Subgroup Analysis 2 (Participants with mental health conditions): P: Participants with mental health conditions~ I: Varied mindfulness interventions C: Varied comparators~ O: Varied scales~	Jazaieri et al., 2012 Zhang et al., 2018 Lindsay et al., 2019	SMD = −0.23 (−0.80, 0.33) I2 = 62.8%, p = 0.068
Subgroup Analysis 3.1 (Younger populations only): P: Younger populations only~ I: Varied mindfulness interventions C: Varied comparators~ O: Varied scales~	Mascaro et al., 2018 Zhang et al., 2018	SMD = −0.85 (−1.36, −0.35)* I2 = 0.0%, p = 0.751
Subgroup Analysis 3.2 (Adults and elderly only): P: Adults and elderly only~ I: Varied mindfulness interventions C: Varied comparators~ O: Varied scales~	Creswell et al., 2012 Jazaieri et al., 2012 Dodds et al., 2015 Lee et al., 2019 Lindsay et al., 2019	SMD = −0.12 (−0.43, 0.19)@ I2 = 18.0%, p = 0.300 SMD = −0.15 (−0.46, 0.15) I2 = 15.6%, p = 0.315
Explorative Analysis 1: P: 3 no known mental health conditions, 1 with elevated stress~ I: Varied mindfulness interventions C: 3 Wait-list and 1 Active control~ O: UCLA-R scale	Creswell et al., 2012 Dodds et al., 2015 Mascaro et al., 2018 Lindsay et al., 2019	MD = −3.74 (−8.45, 0.98) I2 = 64.3%, p = 0.039
Explorative Analysis 2: P: 3 no known mental health conditions, 1 with elevated stress and 1 with SAD~ I: Varied mindfulness interventions C: 3 Wait-list and 1 aerobic exercise~ O: UCLA-R scale and 1 UCLA-8 scale~	Creswell et al., 2012 Jazaieri et al., 2012 Dodds et al., 2015 Mascaro et al., 2018 Lindsay et al., 2019	SMD = −0.33 (−0.76, 0.10) I2 = 53.6%, p = 0.071
Explorative Analysis 3: P: 1 no known mental health conditions and 1 with SAD~ I: MBSR only~ C: Wait-list O: UCLA-R scale and 1 UCLA-8 scale~	Creswell et al., 2012 Jazaieri et al., 2012	SMD = −0.48 (−1.02, 0.06) I2 = 13.9%, p = 0.281
Explorative Analysis 4: P: Varied characteristics (with and without known mental health conditions)~ I: Varied mindfulness interventions C: Varied comparators~ O: Varied scales~	Creswell et al., 2012 Jazaieri et al., 2012 Dodds et al., 2015 Mascaro et al., 2018 Zhang et al., 2018 Lee et al., 2019 Lindsay et al., 2019	SMD=-0.34 (−0.69, 0.01)@ I2 = 48.8%, p = 0.068 SMD = −0.36 (−0.70, −0.03)* I2 = 45.6%, p = 0.088

P, Participant; I, Intervention; C, Comparator; O, Outcome; CBCT, Cognitively-based compassion training; MBSR, Mindfulness-Based Stress Reduction; SAD, Social anxiety disorder.

^~Characteristics of PICO which differ from main analysis no.1.

^@Conservative estimate from Lee et al. (2019).

^*Statistically significant result.