Implementation dosage and depressive symptoms following school-based mindfulness and relaxation: Complier Average Causal Effect estimation in the INSPIRE cluster randomised trial.
Emma Thornton, Christopher Knowles, Margarita Panayiotou, Joao Santos, Emma Ashworth, Carla Mason, Daniel Hayes, Abigail Thompson, Jessica Deighton, Rosie Mansfield, Anna March, Paul Stallard, Neil Humphrey
European Child & Adolescent Psychiatry August 12, 2026 DOI: 10.1007/s00787-026-03152-x (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Complier average causal effect (CACE) analysis within a cluster randomised controlled trial Randomized Peer reviewed |
|---|---|
| Sample size | 14,390 |
| Population | Primary and secondary school pupils in the INSPIRE cluster randomised trial (mindfulness primary: 65 schools, N=3,630; mindfulness secondary: 29 schools, N=3,708; relaxation primary: 66 schools, N=3,800; relaxation secondary: 26 schools, N=3,252) |
| Interventions | Relaxation techniques Mindfulness-based exercises |
| Dose | Relaxation primary: moderate 320 min, high 376 min; Mindfulness primary: moderate 325 min, high 393 min; Mindfulness secondary: moderate 207 min, high 285 min; Relaxation secondary: moderate 180 min, high 275 min |
| Topics | Meditation |
| Keywords | Relaxation Intervention dosage Universal school-based interventions |
| Key findings | Although intent-to-treat findings were null, compliance to relaxation and mindfulness interventions was associated with significant changes in depressive symptoms, with effects differing by intervention type and educational phase. In primary schools, relaxation reduced symptoms (d=-1.52 to -1.48) while mindfulness increased them (d=0.32 to 0.48); in secondary schools, mindfulness reduced symptoms (d=-1.15 to -1.40) while relaxation increased them (d=0.67 to 0.83). The authors argue that effects depend on a minimally effective dose and that these interventions may not be appropriate in all contexts, potentially causing iatrogenic effects. |
Abstract
Implementation variability is hypothesized to be a key treatment effect modifier of universal, school-based mental health interventions, but the evidence base remains meagre. We used Complier Average Causal Effect (CACE) estimation to determine if dosage variability modified treatment effects of relaxation techniques and mindfulness-based exercises in the INSPIRE cluster randomised trial. Analyses were split by phase of education (mindfulness primary: k = 65 primary schools, N = 3,630 pupils; mindfulness secondary: k = 29 secondary schools, N = 3,708 pupils; relaxation primary: k = 66 primary schools, N = 3,800 pupils; relaxation secondary: k = 26 secondary schools, N = 3,252 pupils) and considered compliance effects at the 50th (moderate) and 75th (high) percentiles in the distribution of intervention dosage (total minutes delivered). Despite null intent to treat findings, we observed compliance effects for both interventions. In primary schools, moderate (320 min) and high (376 min) compliance to relaxation techniques significantly reduced depressive symptoms (d=-1.52 and d=-1.48, respectively). In secondary schools, moderate (207 min) and high (285 min) compliance to mindfulness-based exercises also significantly reduced depressive symptoms (d=-1.15 and d=-1.40, respectively). Contrastingly, in primary schools, moderate (325 min) and high (393 min) compliance to mindfulness-based exercises significantly increased depressive symptoms (d = 0.32 and d = 0.48, respectively). In secondary schools, moderate (180 min) and high (275 min) compliance to relaxation techniques also significantly increased depressive symptoms (d = 0.67 and d = 0.83, respectively). The effects of universal, school-based mental health interventions promoting relaxation and mindfulness are contingent on the delivery of a minimally effective dose. However, these interventions may not be appropriate in all educational contexts and could result in iatrogenic effects.Trial registration: Trial registration number: ISRCTN16386254. Trial registration date:04/09/2018.
Comparable studies
Other randomized controlled trials on meditation, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Alterations in Brain and Immune Function Produced by Mindfulness Meditation Healthy employees in a work environment | 2003 | Randomized controlled trial | n = 41 |
| Prevention of relapse/recurrence in major depression by mindfulness-based cognitive therapy. Recovered recurrently depressed patients | 2000 | Randomized controlled trial | n = 145 |
| Open hearts build lives: Positive emotions, induced through loving-kindness meditation, build consequential personal resources. Working adults | 2008 | Randomized controlled trial | n = 139 |
| Short-term meditation training improves attention and self-regulation Undergraduate Chinese students | 2007 | Randomized controlled trial | n = 40 |
| Mindfulness-Based Cognitive Therapy for Depression: Replication and Exploration of Differential Relapse Prevention Effects. Recovered recurrently depressed patients | 2004 | Randomized controlled trial | n = 73 |