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

doi:10.1007/s00787-026-03152-x

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

University of Manchester
Liverpool John Moores University
University College London
Evidence Based Practice Unit

Research output: Contribution to journal › Article › peer-review

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.

Original language	English
Number of pages	14
Journal	European Child and Adolescent Psychiatry
DOIs	https://doi.org/10.1007/s00787-026-03152-x
Publication status	Published - 12 Aug 2026

Data Availability Statement

An anonymised dataset will be made publicly available in the future (planned late 2026). Please contact the Principal Investigator or Trials Manager for further information.

Acknowledgements

We would like to thank all schools, pupils and parents who engaged with or participated in the programme. We would also like to thank the advisory group members, members of the data monitoring and ethics committee and members of the trial steering committee.

Funding

This research was commissioned and funded by the UK Department for Education (DfE). The commissioner and funder of the study had no role in data collection, data analysis, data interpretation or writing of the report. DfE selected the interventions to be trialled and chaired an advisory group of researchers and educators regarding the progress and quality of the research. Views expressed herein are those of the authors and not necessarily the views of the DfE.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 3 Good Health and Well-being

Keywords

Cluster randomised controlled trial
Complier average causal effect analysis
Intervention dosage
Mindfulness
Relaxation
Universal school-based interventions

ASJC Scopus subject areas

Pediatrics, Perinatology, and Child Health
Developmental and Educational Psychology
Psychiatry and Mental health

Access to Document

10.1007/s00787-026-03152-xLicence: CC BY

Cite this

Thornton, E., Knowles, C., Panayiotou, M., Santos, J., Ashworth, E., Mason, C., Hayes, D., Thompson, A., Deighton, J., Mansfield, R., March, A., Stallard, P., & Humphrey, N. (2026). Implementation dosage and depressive symptoms following school-based mindfulness and relaxation: Complier Average Causal Effect estimation in the INSPIRE cluster randomised trial. European Child and Adolescent Psychiatry. https://doi.org/10.1007/s00787-026-03152-x

Implementation dosage and depressive symptoms following school-based mindfulness and relaxation: Complier Average Causal Effect estimation in the INSPIRE cluster randomised trial. / Thornton, Emma; Knowles, Christopher; Panayiotou, Margarita et al.
In: European Child and Adolescent Psychiatry, 12.08.2026.

Research output: Contribution to journal › Article › peer-review

Thornton, E, Knowles, C, Panayiotou, M, Santos, J, Ashworth, E, Mason, C, Hayes, D, Thompson, A, Deighton, J, Mansfield, R, March, A, Stallard, P & Humphrey, N 2026, 'Implementation dosage and depressive symptoms following school-based mindfulness and relaxation: Complier Average Causal Effect estimation in the INSPIRE cluster randomised trial', European Child and Adolescent Psychiatry. https://doi.org/10.1007/s00787-026-03152-x

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AU - Santos, Joao

AU - Ashworth, Emma

AU - Mason, Carla

AU - Hayes, Daniel

AU - Thompson, Abigail

AU - Deighton, Jessica

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AB - 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.

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Implementation dosage and depressive symptoms following school-based mindfulness and relaxation: Complier Average Causal Effect estimation in the INSPIRE cluster randomised trial

Abstract

Data Availability Statement

Acknowledgements

Funding

UN SDGs

Keywords

ASJC Scopus subject areas

Access to Document

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Cite this