Challenges and solutions for N-of-1 design studies in health psychology

• Published in: Health psychology review Vol. 13; no. 2; pp. 163 - 178
• Main Authors: Kwasnicka, Dominika, Inauen, Jennifer, Nieuwenboom, Wim, Nurmi, Johanna, Schneider, Annegret, Short, Camille E., Dekkers, Tessa, Williams, A. Jess, Bierbauer, Walter, Haukkala, Ari, Picariello, Federica, Naughton, Felix
• Format: Journal Article
• Language: English
• Published: England Routledge 03.04.2019; Taylor & Francis Ltd
• Subjects: Appropriateness; Behavior change; Challenges; Change agents; Evaluation; Health behavior; Health psychology; idiographic design; Intervention; N-of-1; Power; Problem solving; Research methodology; single case study; Suitability; within-person design; idiographic design; single case study; within-person design; N-of-1
• ISSN: 1743-7199; 1743-7202
• DOI: 10.1080/17437199.2018.1564627

Theories of behaviour change and health behaviour change interventions are most often evaluated in between-person designs. However, behaviour change theories apply to individuals not groups and behavioural interventions ultimately aim to achieve within-person rather than between-group change. Within-person methodology, such as N-of-1 (also known as single case design), can circumvent this issue, though has multiple design-specific challenges. This paper provides a conceptual review of the challenges and potential solutions for undertaking N-of-1 studies in health psychology. Key challenges identified include participant adherence to within-person protocols, carry-over and slow onset effects, suitability of behaviour change techniques for evaluation in N-of-1 experimental studies, optimal allocation sequencing and blinding, calculating power/sample size, and choosing the most suitable analysis approach. Key solutions include involving users in study design, employing recent technologies for unobtrusive data collection and problem solving by design. Within-person designs share common methodological requirements with conventional between-person designs but require specific methodological considerations. N-of-1 evaluation designs are appropriate for many though not all types of interventions. A greater understanding of patterns of behaviours and factors influencing behaviour change at the within-person level is required to progress health psychology into a precision science. Video abstract: Supplementary Material 1.