title: Efficacy of theory-based interventions for young people with type 1 diabetes: a systematic review and meta-analysis.
abstract: OBJECTIVE
  Theory-based behaviour change interventions have been recommended to improve outcomes for young people with type 1 diabetes. However, theory has exclusively been considered in a simplistic all-or-none fashion. We therefore (1) examined the nature and extent of explicit theory use in published interventions involving young people with type 1 diabetes and (2) the relationship between how theory is used and intervention outcomes.
  
  
  METHODS
  We conducted systematic searches for randomized controlled trials (RCTs) published between 1999 and 2012. We used a detailed structured framework to code how theory was used and meta-analytic techniques to examine the relationships between theory use and intervention efficacy.
  
  
  RESULTS
  We identified 34 articles comprising 27 RCTs. Thirty per cent (k = 8) did not use theory in any of the ways assessed. Where present, the most common use of theory was providing evidence that a targeted theoretical construct predicted behaviour (k = 15; 56%). Trials that used theory to some extent had marginally larger pooled effect sizes for both medical and psychological outcomes than those that did not. However, in meta-regression models, use of theory did not significantly predict intervention outcomes.
  
  
  CONCLUSIONS
  Theory is under-utilized in intervention development for young people with type 1 diabetes. When employed, theory appears to be advantageous, but not necessarily predictive of intervention success. We argue that greater emphasis is needed on choosing appropriate theory, which should then become central to the process of intervention development. Statement of contribution What is already known on this subject? Interventions for young people with type 1 diabetes that explicitly cite a theoretical basis may be more effective than those that do not. Recommendations have been made for theory to be central to the intervention development process in this area. What does this study add? Theory use in recent interventions for young people with type 1 diabetes is extremely limited. Larger positive medical and psychological outcomes are observed in interventions making some use of theory. Greater use of theory does not necessarily guarantee intervention success.
authors.affiliation: Department of Psychology, University of Sheffield, UK; Division of Primary Care, School of Medicine, University of Nottingham, UK; NIHR CLAHRC for South Yorkshire, Sheffield, UK.
authors.forename: Kieran
authors.initials: K
authors.lastname: Ayling
authors.forename: Samantha
authors.initials: S
authors.lastname: Brierley
authors.forename: Barbara
authors.initials: B
authors.lastname: Johnson
authors.forename: Simon
authors.initials: S
authors.lastname: Heller
authors.forename: Christine
authors.initials: C
authors.lastname: Eiser
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000523:psychology* / Q000628:therapy*; D019317:Evidence-Based Medicine / Q000379:methods*; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D010353:Patient Education as Topic / Q000379:methods*; D016032:Randomized Controlled Trials as Topic; D016896:Treatment Outcome; D055815:Young Adult
keywords: behaviour change; diabetes; interventions; theory; young people