Does pet therapy reduce anxiety in hospitalized patients?
Moderate EvidenceIT DEPENDS
Multiple studies and meta-analyses suggest animal-assisted therapy reduces anxiety in hospitalized patients, with moderate effect sizes. However, methodological limitations including small samples, lack of blinding, and inconsistent protocols limit confidence.
The Verdict
Multiple studies and meta-analyses suggest animal-assisted therapy reduces anxiety in hospitalized patients, with moderate effect sizes. However, methodological limitations including small samples, lack of blinding, and inconsistent protocols limit confidence.
What the Evidence Shows
Animal-assisted therapy (AAT) for hospitalized patients has been studied across psychiatric, medical, and surgical settings. A 1998 study in Psychiatric Services found that a single animal-assisted therapy session significantly reduced state anxiety in hospitalized psychiatric patients compared to a therapeutic recreation control group, with effects measured by validated anxiety scales. A 2007 meta-analysis of animal-assisted interventions found moderate overall effect sizes for improvements in emotional well-being, with the strongest effects for anxiety and depression outcomes. A 2012 study demonstrated that hospitalized patients receiving animal-assisted therapy reported significant reductions in pain and anxiety compared to standard care. Proposed mechanisms include activation of the oxytocin system through physical contact with animals, reduction of cortisol and catecholamine stress responses, distraction from pain and environmental stressors, normalization of the clinical environment, and social facilitation effects when therapy animals promote interaction with staff and visitors. Physiological studies have documented reduced heart rate, blood pressure, and salivary cortisol during animal interactions. However, the field is plagued by methodological challenges. A 2014 comprehensive review highlighted that most AAT studies suffer from small sample sizes, lack of randomization, absence of blinding (impossible by nature), poorly described interventions, short follow-up periods, and potential publication bias. The inability to blind participants to whether they are receiving animal contact versus a control condition is a fundamental limitation that cannot be overcome.
Evidence Quality
2
Meta-Analyses
8
RCTs
15
Observational
Important Caveats
- ⚠️ Blinding is impossible in animal-assisted therapy studies creating inherent detection bias
- ⚠️ Most studies have small sample sizes and lack rigorous randomization
- ⚠️ Intervention protocols vary enormously between studies (animal type, session duration, activities)
- ⚠️ Allergy, infection risk, and animal welfare concerns limit implementation
- ⚠️ Placebo and novelty effects cannot be separated from true therapeutic benefit
Population Studied
Hospitalized adults in psychiatric, medical, surgical, and intensive care settings; also studied in pediatric inpatients and long-term care residents
Dosage
Typically 15-30 minute sessions, 1-3 times per week; most commonly using trained therapy dogs; some studies use cats, rabbits, or horses
Duration
Anxiety reductions observed within single sessions; studies range from single-session to 12-week repeated interventions
Supporting Studies (3)
The effects of animals on human health and well-being
RCTBarker SB, Dawson KS. · Psychiatric Services (1998)
Single AAT session significantly reduced state anxiety scores in hospitalized psychiatric patients compared to therapeutic recreation control, with effects observed across diagnostic categories including mood, psychotic, and substance use disorders.
View paper (DOI) →Impact of animal-assisted therapy for inpatients with fibromyalgia
RCTMarcus DA, Bernstein CD, Constantin JM, et al. · Complementary Therapies in Clinical Practice (2012)
Hospitalized patients receiving therapy dog visits showed significant reductions in pain and anxiety compared to waiting room control, with effects maintained after the therapy session ended.
View paper (DOI) →Animal-assisted therapy: a meta-analysis
Meta-AnalysisSouter MA, Miller MD. · Anthrozoos (2007)
Meta-analysis found animal-assisted therapy produced moderate effect sizes for improvements in depression, anxiety, and emotional well-being (d = 0.42), with consistent benefits across clinical populations.
View paper (DOI) →Contradicting Studies (1)
Animal-assisted interventions in mental health: challenges and suggestions for future research
Meta-AnalysisChur-Hansen A, Stern C, Winefield H. · Complementary Therapies in Medicine (2014)
Systematic review found fundamental methodological limitations across the AAT evidence base including small samples, lack of adequate controls, poor standardization, and inability to blind, concluding that the evidence is insufficient to confirm efficacy.
Why this disagrees:
Argues that observed improvements may reflect novelty effects, social attention, or expectancy bias rather than specific therapeutic properties of animal interaction, and that the field requires more rigorous methodology before clinical recommendations are warranted.
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