Participants
Student sample sizes were reported in all 13 papers in the review with a total number of 2277 early adolescent participants. The seven quantitative papers had a total of 1721 participating students, ranging from 41 (Sibinga et al. 2013) to 555 students (Johnson et al. 2017). The six mixed-method papers had a total of 556 participating students, ranging from 30 (Arthurson 2015) to 175 students (Joyce et al. 2010). The gender of students was reported in all studies except one (Arthurson 2015). Of the studies that reported gender, all had a mix of both male and female students, except one study that only had male students (Sibinga et al. 2013). In the 12 studies where gender was reported, 49% of students were females.
All of the studies provided information on student’s age. Two of the papers reported age range between 11 and 12 years (Arthurson 2015; Costello and Lawler 2014), one study reported age range between 11 and 13 years (Viafora et al. 2015) and the remaining ten studies reported a mean age between 11 and 14 years, with a minimum mean age of 11.1 years (Schonert-Reichl and Lawlor 2010) and a maximum mean age of 13.63 years (Johnson et al. 2016). Students attended either upper primary school, middle school or lower high schools. Of the 13 studies, two were conducted with private schools (Arthurson 2015; Britton et al. 2014), six with public schools (Barnes et al. 2004; Costello and Lawler 2014; Schonert-Reichl and Lawlor 2010; Sibinga et al. 2013, 2016; Viafora et al. 2015), two had students from both public and private schools (Johnson et al. 2016, 2017) and three did not provide this information (Bernay et al. 2016; Joyce et al. 2010; Quach et al. 2016).
Objectives
All 13 of the papers under review examined the effect of a MBI for the well-being of early adolescent school-aged students. Twelve of the 13 papers examined well-being through student self-report measures as either an increase in positive mental health traits for the student (e.g. optimism, coping, self-compassion, self-concept and emotion regulation) (Arthurson 2015; Bernay et al. 2016; Schonert-Reichl and Lawlor 2010; Sibinga et al. 2013; Viafora et al. 2015), or as a reduction in negative mental health traits (e.g. anxiety, depression and stress) (Britton et al. 2014; Costello and Lawler 2014; Johnson et al. 2016, 2017; Joyce et al. 2010; Quach et al. 2016; Sibinga et al. 2013, 2016). One paper (Barnes et al. 2004) aimed to evaluate the effect of a MBI on physiological measures (e.g. blood pressure, heart rate).
In addition to the well-being-related outcomes, the effects of a MBI on cognitive functioning (Quach et al. 2016) were evaluated, along with intervention effects of home practice (Johnson et al. 2016) and parental involvement (Johnson et al. 2017). Finally, six of the studies aimed to better understand the acceptability and feasibility of implementing the program at school from students’ and/or teachers’ perspectives (Arthurson 2015; Bernay et al. 2016; Britton et al. 2014; Costello and Lawler 2014; Joyce et al. 2010; Viafora et al. 2015).
Facilitators
The facilitators who deliver the program are part of MBI interventions and their importance cannot be overemphasised (Hwang et al. 2017). It is believed that extensive and ongoing practice in mindfulness is required by the facilitator in order to best support the delivery of a MBI (Segal et al. 2002). In the 13 papers reviewed, 12 of the papers identified the facilitator of the program as either a teacher at the school (n = 6) (Arthurson 2015; Barnes et al. 2004; Britton et al. 2014; Costello and Lawler 2014; Joyce et al. 2010; Schonert-Reichl and Lawlor 2010) or an external facilitator (n = 6) (Bernay et al. 2016; Johnson et al. 2016, 2017; Quach et al. 2016; Sibinga et al. 2013; Viafora et al. 2015). Three of the studies provided no information on the training or experience of the instructor (Barnes et al. 2004; Bernay et al. 2016; Sibinga et al. 2016), with many others providing very little detail.
Of the 13 studies reviewed, five reported the instructor had a long-standing personal mindfulness practice (Britton et al. 2014; Johnson et al. 2016, 2017; Quach et al. 2016; Sibinga et al. 2013) and indicated the instructor had undertaken mindfulness training above that of a 1-day session (Johnson et al. 2016, 2017; Quach et al. 2016; Sibinga et al. 2013; Viafora et al. 2015). In addition to this, seven studies reported that the intervention was delivered by more than one instructor in their study (Bernay et al. 2016; Britton et al. 2014; Costello and Lawler 2014; Joyce et al. 2010; Quach et al. 2016; Schonert-Reichl and Lawlor 2010; Sibinga et al. 2016), which makes it difficult to ensure consistency and fidelity of the intervention program. Of these seven studies taught by multiple instructors, only two (Quach et al. 2016; Schonert-Reichl and Lawlor 2010) reported fidelity of the intervention program.
Two of the studies reviewed were delivered by the same facilitator (Johnson et al. 2016, 2017). This external facilitator was reported as having 10 years of personal practice with mindfulness, along with training in mindfulness programs and prior experience in delivery to this age group of students. This description indicates that the facilitator in the two studies was more experienced than facilitators in most of the other studies included in this review. This is worth noting as both of these studies did not find any positive intervention effects.
Intervention Content and Duration
In examining the intervention details, 11 of the 13 studies in the review provided detailed information on the intervention (Arthurson 2015; Barnes et al. 2004; Bernay et al. 2016; Britton et al. 2014; Costello and Lawler 2014; Johnson et al. 2016, 2017; Joyce et al. 2010; Quach et al. 2016; Schonert-Reichl and Lawlor 2010; Viafora et al. 2015). However, the format, structure and duration of the program delivered in each of these papers varied widely. Whilst a general consensus on a definition of mindfulness has not been reached, it has been operationalised as “paying attention on purpose, in the present moment, and non-judgementally to the unfolding of experience moment by moment” (Kabat-Zinn 2003, p.145). These programs are taught around a combination of practices, including formal activities (e.g. body scan meditation, sitting meditation) and informal activities (e.g. mindful eating, walking or listening), and generally include a component of both didactic and experiential learning.
Six papers stated that the program was adapted from the Mindfulness-Based Stress Reduction (MBSR) program (Barnes et al. 2004; Costello and Lawler 2014; Joyce et al. 2010; Quach et al. 2016; Sibinga et al. 2013, 2016), and two studies stated that they delivered the Mindfulness in Schools Project (MiSP) program (Johnson et al. 2016, 2017). The experiential exercise of breath awareness was identified in ten of the studies (Barnes et al. 2004; Bernay et al. 2016; Britton et al. 2014; Costello and Lawler 2014; Johnson et al. 2016, 2017; Joyce et al. 2010; Quach et al. 2016; Schonert-Reichl and Lawlor 2010; Viafora et al. 2015), with loving-kindness identified as a theme in two of the papers (Bernay et al. 2016; Schonert-Reichl and Lawlor 2010). Whilst all the studies provided both experiential and didactic learning, seven of the papers highlighted the component of instructor-led discussion in the program (Barnes et al. 2004; Johnson et al. 2016, 2017; Joyce et al. 2010; Quach et al. 2016; Sibinga et al. 2016; Viafora et al. 2015). A curriculum manual was documented in four of the papers to guide the instructor (Costello and Lawler 2014; Johnson et al. 2016, 2017; Schonert-Reichl and Lawlor 2010). One paper reported a descriptive rather than a prescriptive approach was used to deliver the program (Joyce et al. 2010), which can challenge the fidelity of intervention and replicability of the study if a novice facilitator delivers the intervention and no plan is in place to ensure intervention fidelity.
The duration of the program delivered ranged from short daily sessions to longer weekly sessions. The shortest daily program was reported to be between 3 and 12 min (Britton et al. 2014; Costello and Lawler 2014), and the longest weekly program was 1 h in duration (Bernay et al. 2016). The number of weeks the program was offered ranged from 4 (Quach et al. 2016) to 12 weeks (Sibinga et al. 2013). The shortest dosage of mindfulness was reported in programs that offered short daily lessons, which totalled between 187 (Costello and Lawler 2014) and 225 min (Britton et al. 2014) for the duration of the program. The longest dosage was reported in a program combining a weekly longer lesson with short practices three times a day for 9 weeks, totalling 810 min of mindfulness (Schonert-Reichl and Lawlor 2010). The longest single weekly lessons reported a range of between 380 min (Johnson et al. 2016) and 600 min (Barnes et al. 2004; Sibinga et al. 2013).
Home practice was an optional exercise offered in seven of the studies (Barnes et al. 2004; Johnson et al. 2016, 2017; Joyce et al. 2010; Quach et al. 2016; Sibinga et al. 2016; Viafora et al. 2015) and is worth noting as mindfulness homework has been shown to be an important element of mindfulness training (Semple et al. 2006). In addition to this, one of the studies invited parental involvement in the program by offering a 1-h information session on the intervention, followed by 10-min YouTube clips on lesson material weekly (Johnson et al. 2017). The findings from this study found no significant effect on parental involvement, but it is worth noting that parental involvement was extremely low. Parental post course feedback was 8% and the parents who viewed the YouTube clip had also reduced to 9% at the end of the course. Similarly, teacher uptake on the program in this study was also low.
Intervention Measures and Effects
Different measures were used in each of the studies to determine MBI effect and 11 out of the 13 studies reported positive effects on different well-being variables (Arthurson 2015; Barnes et al. 2004; Bernay et al. 2016; Britton et al. 2014; Costello and Lawler 2014; Joyce et al. 2010; Quach et al. 2016; Schonert-Reichl and Lawlor 2010; Sibinga et al. 2013, 2016; Viafora et al. 2015). Of the seven quantitative papers in the review, three relied exclusively on student self-report measures (Johnson et al. 2016, 2017; Sibinga et al. 2016), which can be an issue considering the social desirability bias that can arise when relying solely on self-report measures in examining the effects of an intervention (Creswell 2015). Of the remaining four quantitative design studies, in addition to self-report measures, physical measures (e.g. heart rate, sleeping patterns, salivary cortisol) (Barnes et al. 2004; Sibinga et al. 2013), cognitive assessment (Quach et al. 2016) and teacher-rated report (Schonert-Reichl and Lawlor 2010) were employed. All six of the mixed-method design studies used self-report measures. In addition to this, qualitative data were gathered from both students and teachers. Student experiences were recorded through the use of student journals or open-ended questionnaires (Joyce et al. 2010; Viafora et al. 2015), student classroom observations (Arthurson 2015) or through student interviews (Bernay et al. 2016; Costello and Lawler 2014). Teachers’ experiences with implementing MBIs were recorded through observations and journals (Bernay et al. 2016; Joyce et al. 2010) and interviews (Arthurson 2015; Costello and Lawler 2014; Joyce et al. 2010).
Of the 11 quantitative design studies reviewed, nine studies (Barnes et al. 2004; Bernay et al. 2016; Britton et al. 2014; Joyce et al. 2010; Quach et al. 2016; Schonert-Reichl and Lawlor 2010; Sibinga et al. 2013, 2016; Viafora et al. 2015) reported positive improvements on physiological, cognitive and emotional well-being from pre- to post-test measures. These positive improvements were reported on blood pressure and heart rate (Barnes et al. 2004), working memory capacity (Quach et al. 2016, partial η2 = .24, p < .001) and an increase in mindfulness (Viafora et al. 2015). Positive improvements were also reported in self-reported emotional well-being measures that examined an increase in positive mental health traits and/or a reduction in negative mental health traits. An increase in positive mental health traits was reported on optimism and positive affect (Schonert-Reichl and Lawlor 2010, partial η2 = .018, p < .05 and partial η2 = .009, p < .10, respectively), improved well-being (Bernay et al. 2016, partial η2 = .04, p = .008) and prosocial functioning (Joyce et al. 2010, Cohen’s d = .21, p < .05).
A reduction in negative mental health traits were reported in outcome variables including suicidal ideation and affective disturbances (Britton et al. 2014, likelihood ratio = 7.73, p = .005 and Cohen’s d = .41, p = .05, respectively), depression (Joyce et al. 2010, Cohen’s d = .27, p < .01; Sibinga et al. 2016), negative coping (Sibinga et al. 2013, Cohen’s d = .87, p = .06), negative affect, self-hostility, rumination (Sibinga et al. 2016) and anxiety (Sibinga et al. 2013, Cohen’s d = .79, p = .01). One study also reported an increase in mindfulness in the intervention group at 3-month follow-up (Bernay et al. 2016, partial η2 = .05, p = .005). Teacher-rated measures reported positive improvements from pre- to post-test measures in Schonert-Reichl and Lawlor’s (2010) study on student behaviour (partial η2 = .074, p < .001), attention (partial η2 = .120, p < .001), emotional regulation (partial η2 = .041, p < .001) and social and emotional competence (partial η2 = .260, p < .001). Positive improvements were also reported on post-test teacher-rated measures on classroom climate (Bernay et al. 2016).
Effect sizes were reported in eight of the 11 quantitative papers (Bernay et al. 2016; Britton et al. 2014; Johnson et al. 2016, 2017; Joyce et al. 2010; Quach et al. 2016; Schonert-Reichl and Lawlor 2010; Sibinga et al. 2013). They together formed an overall pattern as decreases in negative mental traits (e.g. affective disturbances, anxiety) were often reported with medium to large effect sizes while small effect sizes were reported for increases in positive mental traits (e.g. positive affect, prosocial functioning), except for working memory capacity (Quach et al. 2016, partial η2 = .24, p < .001). Two studies reported no positive improvement in the MBI (Johnson et al. 2016, 2017) at all time intervals across the primary outcome variables, including depression, anxiety and mindful awareness.
Practice and Experience
Secondary analysis of the qualitative findings of six mixed-method studies generated two major themes: students’ experiences of practising mindfulness and teachers’ experiences of implementing mindfulness programs. Students’ experiences of practising mindfulness consisted of student response, practice experience and perceived benefits (Fig. 2), while teachers’ experience of implementing mindfulness consisted of student response, enablers of and barriers to successful implementation and perceived benefits for students (Fig. 3).
Students’ Experiences of Practising Mindfulness
Student Response
When mindfulness was introduced in class, overall responses from students were positive and active. All (Bernay et al. 2016) or the majority of students (Arthurson 2015; Costello and Lawler 2014; Viafora et al. 2015) were engaged with the practice. It was perceived to be “fun” (Costello and Lawler 2014) and “helpful” (Arthurson 2015; Viafora et al. 2015). Some students, however, found it boring (Britton et al. 2014) and difficult to practise because of invasive thoughts, mind wandering and recurring thoughts (Costello and Lawler 2014). Sitting still also provoked a feeling of sadness and fatigue (Arthurson 2015). A minority of students disliked the practice (Arthurson 2015; Britton et al. 2014) and rejected it by means of daydreaming and classroom disruption (Britton et al. 2014).
Practice Experience
Students engaged with practice by slowing down and taking time to notice what is here and now (Bernay et al. 2016). Mindful breathing was used most frequently to anchor their mind to the present, and this had calming effects (Arthurson 2015; Bernay et al. 2016; Costello and Lawler 2014; Viafora et al. 2015). Slow eating allowed the experience of long-lasting flavour (Bernay et al. 2016) and discovery of a new relationship with food (Arthurson 2015). Students applied what they learned and practised during the sessions at home, school and playgrounds to deal with family-related stress and difficult social interactions (Bernay et al. 2016; Costello and Lawler 2014; Viafora et al. 2015). Students became aware of when their minds wandered and learned to bring it back (Arthurson 2015; Costello and Lawler 2014). Awareness grew as they noticed mental and physical events they previously had not, such as bodily movements associated with breathing and precursory signs of panicking (Bernay et al. 2016; Costello and Lawler 2014). For some students, mindfulness practice helped them to pay attention to the feelings of others, which gave rise to kind actions such as sharing lunch with a student who was alone (Bernay et al. 2016).
Perceived Benefits
Practice engagement appears to be closely associated with seeing change. The pattern is that engaging with practice leads to seeing positive change in physical, mental and relational experiences, which contributes to further engagement with practice. Such change consisted of perceived benefits that manifested in a wide range of ways. Students mentioned psychological benefits most frequently, as they used meditation practices for their coping strategies (Arthurson 2015; Bernay et al. 2016; Costello and Lawler 2014; Viafora et al. 2015). Breathing meditation, for example, helped them feel calm and relaxed, which reduced stress, worry and anxiety, and increased concentration (Arthurson 2015; Bernay et al. 2016; Britton et al. 2014; Costello and Lawler 2014; Viafora et al. 2015). It also improved sleep quality (Arthurson 2015).
Emotion and behaviour regulation naturally occurred as students became aware of signs of anger and stress, felt the weakening of anger and stress by focusing on breathing and therefore stopped these signs from feeding into acting out (Bernay et al. 2016; Costello and Lawler 2014; Viafora et al. 2015). Behaviour regulation helped students make friends (Bernay et al. 2016) and improved their classroom behaviour (Costello and Lawler 2014). Management of psychological stress and test anxiety (Bernay et al. 2016; Costello and Lawler 2014), reductions of disruptive behaviours in class (Costello and Lawler 2014; Viafora et al. 2015) and enhancement of concentration (Bernay et al. 2016; Britton et al. 2014; Costello and Lawler 2014; Viafora et al. 2015) together contributed to student academic learning.
Teachers’ Experiences of Implementing Mindfulness Programs
Student Response
Arthurson (2015) and Joyce et al. (2010) reported teachers’ experiences of delivering mindfulness activities in their class. Generally, teachers were positive about teaching mindfulness and found the majority of their students engaged with the activities they taught (Joyce et al. 2010). Different activities appealed to students differently, with students finding at least one activity enjoyable to practise (Arthurson 2015). However, some students had difficulty in taking the activities seriously and participating in the lessons (Joyce et al. 2010).
Enablers of and Barriers to Successful Implementation
Teachers identified a range of enablers that together created environments conducive to the successful implementation of classroom-based mindfulness intervention. They are teachers’ ability to embody mindfulness, collaboration with fellow teachers, support from school administrators and parents, relaxing physical environment and students’ willingness to learn (Joyce et al. 2010). Teachers nominated time pressure and crowded curriculum content as the biggest barrier, along with students’ disengagement with the program (Joyce et al. 2010).
Perceived Benefits for Students
Teachers found their students made psychological, behavioural and learning progress over time from practising mindfulness activities (Arthurson 2015; Costello and Lawler 2014). The most commented-on change was students being relaxed and settled after meditation practices, which reduced disruptive behaviour and increased on-task behaviour as they became less reactive (Costello and Lawler 2014; Joyce et al. 2010).