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Specific and Non-specific Factors of Animal-Assisted Interventions Considered in Research: A Systematic Review

By C. Wagner, C. Grob, K. Hediger

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Research on animal-assisted interventions (AAIs) has increased massively in the last few years. But it is still not clear how AAIs work and how important the animal is in such interventions. The aim of this systematic review was to compile the existing state of knowledge about the working mechanisms of AAIs. We searched 12 major electronic databases for previous AAI studies with active control groups. Of 2001 records identified, we included 172 studies in the systematic review. We extracted previously published hypotheses about working mechanisms and factors that have been implicitly considered specific or non-specific in AAI research by categorizing control conditions using content analysis. We analyzed the categories using descriptive statistics. We found that 84% of the included studies mentioned a hypothesis of working mechanisms, but 16% did not define specific hypotheses. By analyzing their control conditions, we found that in most controlled studies, the animal or the interaction with the animal was implicitly considered as a specific factor for the effects of the AAI. Non-specific factors such as therapeutic aspects, social interactions, or novelty have also been controlled for. We conclude that AAI research still cannot answer the question of how and why AAIs work. To address this important research gap, we suggest using component studies with innovative control conditions and results from placebo research to address both the specific and non-specific, contextual factors of AAIs to disentangle its mechanisms. SYSTEMATIC REVIEW REGISTRATION:, identifier: CRD42020158103.

Date 2022
Publication Title Front Psychol
Volume 13
Pages 931347
ISBN/ISSN 1664-1078 (Print)1664-1078
DOI 10.3389/fpsyg.2022.931347
Author Address Division of Clinical Psychology and Psychotherapy, Faculty of Psychology, University of Basel, Basel, Switzerland.Division of Clinical Psychology and Animal-Assisted Interventions, Faculty of Psychology, University of Basel, Basel, Switzerland.REHAB Basel, Clinic for Neurorehabilitation and Paraplegiology, Basel, Switzerland.Department of Epidemiology and Public Health, Human and Animal Health Unit, Swiss Tropical and Public Health Institute, Allschwil, Switzerland.Faculty of Psychology, Open University, Heerlen, Netherlands.
Additional Language English
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Researchers should cite this work as follows:

  1. Animal-assisted interventions
  2. Conflict
  3. open access
  4. systematic reviews
  1. open access