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

Dominika Kwasnicka, Jennifer Inauen, Wim Nieuwenboom, Johanna Nurmi, Annegret Schneider, Camille E. Short, Tessa Dekkers, A. Jess Williams, Walter Bierbauer, Ari Heikki Haukkala, Federica Picariello, Felix Naughton

Research output: Contribution to journalReview ArticleScientificpeer-review


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.

Original languageEnglish
JournalHealth Psychology Review
Issue number2
Pages (from-to)163-178
Number of pages16
Publication statusPublished - 3 Apr 2019
MoE publication typeA2 Review article in a scientific journal

Fields of Science

  • 5144 Social psychology
  • N-of-1
  • idiographic design
  • single case study
  • within-person design

Cite this

Kwasnicka, D., Inauen, J., Nieuwenboom, W., Nurmi, J., Schneider, A., Short, C. E., ... Naughton, F. (2019). Challenges and solutions for N-of-1 design studies in health psychology. Health Psychology Review, 13(2), 163-178.