Pet Therapy in Hospitals: The Evidence for Animal-Assisted Therapy

By Sarah Bennett, Certified Animal Nutritionist

The sight of a golden retriever padding quietly through a hospital ward might seem incongruous — a domestic creature in a world of antiseptic and clinical precision. But a growing body of peer-reviewed research is demonstrating that animal-assisted therapy (AAT) is not merely a feel-good addition to patient care but a clinically meaningful intervention with measurable physiological and psychological effects. The question is no longer whether animals help people in medical settings; it is how, for whom, and through what mechanisms.

Animal-assisted therapy has a longer history than most people realize. Florence Nightingale observed in the nineteenth century that small pets appeared to help patients recovering from illness. Sigmund Freud famously kept his dog Jofi in therapy sessions, noting that the dog's presence seemed to calm anxious patients. But systematic, evidence-based research into AAT is a more recent development, and its findings are reshaping how some healthcare institutions approach patient care.

The NIH's Investment in the Evidence Base

The U.S. National Institutes of Health has recognized animal-human interaction as a legitimate field of biomedical inquiry. The NIH launched a dedicated research program to investigate the health benefits of human-animal interaction, funding studies across multiple institutions to examine the biological pathways through which animals affect human health. This institutional recognition has accelerated the publication of high-quality clinical research that is beginning to answer skeptics' questions about the evidence base.

The NIH research initiative specifically focuses on the mechanisms underlying observed benefits: oxytocin release, cortisol reduction, modulation of the autonomic nervous system, and changes in immune markers. Rather than simply documenting that patients feel better after animal visits, this research aims to identify the biological substrates of that improvement — transforming AAT from a promising intervention into one with a mechanistic explanation.

Mental Health Settings: The Strongest Evidence

The evidence for AAT is strongest in mental health settings, where the intervention has been studied most extensively. Patients with depression, anxiety, PTSD, and schizophrenia have all been examined in controlled studies, and the results are consistently positive, if variable in effect size.

For anxiety, the evidence is particularly compelling. Multiple studies have found that brief animal-assisted interactions reduce self-reported anxiety, lower cortisol levels, and decrease physiological markers of stress such as skin conductance and heart rate variability. These effects have been observed in psychiatric inpatients, surgical patients awaiting procedures, and individuals undergoing chemotherapy — populations for whom anxiety management is both a quality-of-life and a medical priority.

As Science Daily reported on a major 2020 study, even brief AAT sessions of ten to fifteen minutes produced significant reductions in pain perception and anxiety among hospital patients. The effects were comparable to some pharmacological interventions for mild anxiety, with the significant advantage of having no adverse side effects — a consideration of growing relevance in healthcare systems trying to reduce medication burden.

AAT in the NHS and European Healthcare Systems

The United Kingdom's National Health Service has been cautiously embracing animal-assisted therapy in certain settings. As The Guardian reported, NHS mental health trusts in several regions have introduced therapy dog programmes into inpatient psychiatric wards, finding that the animals help reduce incidents of patient agitation, facilitate communication between patients and staff, and improve ward atmosphere in ways that have practical benefits beyond the subjective.

Ward staff reported that therapy dog visits created a natural context for conversations between patients who might otherwise not interact, and between patients and nurses — a social lubricant effect well documented in community settings but now being applied in clinical environments. For long-stay psychiatric patients, in particular, the routine of anticipating and caring for visiting animals provides structure and emotional engagement that supplements formal therapeutic interventions.

Pain Management: An Underexplored Application

One of the more surprising findings in AAT research concerns pain management. Several studies have found that animal-assisted interactions reduce patients' subjective experience of pain — not merely their reported anxiety about pain, but their actual pain scores on validated clinical scales. This effect has been observed in children undergoing painful medical procedures, adults in chronic pain management programmes, and post-surgical patients.

The proposed mechanism involves the endogenous opioid system. Positive social interactions, including those with animals, are associated with release of endorphins — the body's own pain-modulating neurotransmitters. Animal contact may also redirect attentional resources away from pain processing, a phenomenon related to the well-documented role of distraction in pain management. Whatever the mechanism, pain reduction without pharmacological intervention is a clinically significant finding, particularly for populations where opioid use carries risks.

Paediatric Settings: Children and Animals

Some of the most emotionally resonant and scientifically robust AAT research involves children. Paediatric hospital settings are among the most psychologically demanding environments imaginable — frightening procedures, unfamiliar surroundings, separation from home and friends, and physical pain combine to create acute distress in child patients. AAT has shown particular promise in this population.

Studies in paediatric oncology wards have found that children receiving chemotherapy who had access to therapy animal visits reported lower anxiety and nausea scores than controls. Research in paediatric intensive care units has found that animal visits reduce measured stress hormones in child patients. In paediatric dentistry — a setting of particular anxiety for many children — the presence of a trained therapy dog during procedures has reduced the need for sedation in several controlled trials.

Pet Partners, one of the largest animal-assisted therapy organisations in North America, maintains an extensive database of published research across these settings. Their registry of certified therapy animal teams — currently numbering over 13,000 — operates in hospitals, schools, disaster relief settings, and care homes, providing a structured framework for the kind of consistent, documented AAT that enables meaningful research.

Dementia and Cognitive Decline

Perhaps the most poignant application of AAT is in dementia care. Patients with Alzheimer's disease and other dementias often struggle to connect with human caregivers through verbal communication, but consistently show positive responses to animal contact — smiling, reaching out to touch animals, and demonstrating apparent recognition and pleasure even in late-stage disease.

Research in this area has found that AAT sessions reduce agitation in dementia patients, a significant clinical problem associated with distress, danger, and heavy medication use. Regular AAT has also been associated with increased nutritional intake — dementia patients who participated in animal-assisted mealtime programs ate more than controls, possibly because the social stimulation of the animal visits improved overall engagement and appetite.

Some facilities have also introduced robotic animal companions for dementia patients who cannot safely interact with live animals. While robots lack the genuine biological presence of living animals, studies suggest they produce some similar effects — challenging assumptions about what exactly drives AAT's therapeutic mechanisms and suggesting that multiple pathways may be involved.

Addressing Legitimate Concerns: Infection Control and Animal Welfare

The integration of animals into clinical settings is not without challenges. Infection control is the most frequently cited concern. However, major AAT organisations have developed rigorous protocols — regular veterinary health checks, vaccination requirements, bathing before visits, avoidance of high-risk areas such as sterile procedural suites and bone marrow transplant units — that have thus far maintained excellent safety records. Published reviews of AAT safety in clinical settings have found no documented cases of animal-to-patient pathogen transmission when established protocols are followed.

Animal welfare is an equally important consideration. Therapy animals are working in demanding, high-stimulation environments that carry potential for stress. Responsible AAT programmes carefully monitor animal stress indicators, limit visit duration and frequency, and retire animals showing signs of work-related anxiety. The welfare of the therapy animal is not a footnote to the therapy programme; it is central to the programme's ethical foundation and, practically, to its effectiveness — stressed animals do not provide therapeutic contact in the same way that calm, well-adjusted ones do.

The Future of AAT in Healthcare

The trajectory of AAT research suggests a maturing field moving toward greater clinical specificity. Rather than asking whether AAT works in general, researchers are increasingly asking which specific interventions work best for which patient populations, delivered in what format, at what frequency, and alongside which other therapeutic modalities. This is the natural progression of any evidence-based intervention from promising novelty to established practice.

Several hospital systems in the United States, Europe, and Australia have already moved AAT from an informal volunteer activity to a formal component of their therapeutic programming — with dedicated coordinators, structured protocols, and documented outcome measurement. As the evidence base continues to develop, this integration is likely to deepen.

For the patients who have experienced it — the child who stopped crying when the therapy dog arrived, the dementia patient who smiled for the first time in days at the touch of a cat's fur, the surgical patient whose anxiety scores dropped after a fifteen-minute visit — the evidence is already conclusive. The research is catching up with what patients and caregivers have known for decades: in hospital settings, as in the rest of human life, the presence of animals matters.