Table 2.

Characteristics of Interventions of Included Studies

Author	Mindfulness training intervention	Content of intervention	Modifications	Delivery	Frequency and dosage	Adherence	Control condition
Hoge et al., 2013, 2015, 2018, 2020; Hölzel et al., 2013	8-week MBSR	Practice of exercises to build present moment awareness with a non-judgemental attitude	Shorter times were used compared to the original program for classes (2.5 to 2 h), retreat (8 to 4 h) and homework (45 to 20 min). Metta (loving kindness) was added to the first class and homework practice	Group classes taught by MBSR instructor with > 8 years experience	8 × weekly 2-h group classes + 4-h retreat + 20 min daily homework practice	No adherence data reported for Hoge et al., 2013, 2015, 2018, 2020 Hölzel et al., 2013 (N = 26)                                        Homework mins of practice MBSR: M = 1,116, SD = 499 Control: M = 868, SD = 413 Number of classes attended      MBSR: M = 7.27, SD = 0.59 Control: M = 7.00, SD = 0.59 Number of participants who missed the retreat day      MBSR: 26.7% Control: 9.1% No significant group differences found for any measure	8-week stress management education class active control. 8 × weekly 2-h group classes + 4-h special class + 20 min daily homework practice. Content included psychological and physical health information and gentle exercises. Delivered by an instructor with 9 years experience and a physical therapist with 22 years experience
Asmaee Majid et al., 2012	8-week MBSR	As above	Not reported	Group classes delivered by an experienced MBSR instructor	8 × weekly 2-h group classes + 30 min daily homework practice	No adherence data reported	Details of control condition not reported
Wong et al., 2016	8-week MBCT	Exercises to increase present moment awareness of feelings and thoughts and integrate mindfulness skills into daily activities	Cognitive–behavioural components related to anxiety were introduced to replace those previously relating to depression (i.e., theory and education regarding automatic thoughts, avoidance, worrying, action planning, relapse prevention)	Group classes taught by a clinical psychologist and social worker with experience in delivering MBCT	8 × weekly 2-h group classes + 45 min daily homework practice	Number of classes attended MBCT: M = 6.4, SD = 1.9 Psychoeducation group: M = 7.1, SD = 1.5 No significant group differences found in terms of completion. No baseline covariate was found to be associated with compliance (i.e., attendance of > 80% of classes)	1) 8-week Psycho-education group. 8 × weekly 2-h group classes taught by two clinical psychologists with at least two years experience. CBT-informed psychoeducation: stress, panic, insomnia, depression, thinking and behaviours 2) Care as usual. No specific intervention but allowed to access to primary care services (i.e., GP, seek referral to mental health specialist)
Zhao et al., 2019	8-week MBCT	As above	Modified psychoeducation and relapse prevention content to be relevant to GAD	Group classes taught by a psychologist with > 5 years experience in delivering mindfulness meditation	8 × weekly 2-h group classes + 30 min daily homework practice	No adherence data reported	8-week pre-intervention waitlist (within-subjects)

Note. MBSR = Mindfulness Based Stress Reduction; M = Mean; SD = Standard Deviation; MBCT = Mindfulness Based Cognitive Therapy; CBT = Cognitive Behavioural Therapy; GP = General practitioner