Animal-Assisted Therapy: How Pets Help Mental Health

By Sarah Bennett, Certified Animal Nutritionist

The bond between humans and animals is ancient, but its formalisation as a clinical tool is surprisingly recent. Animal-Assisted Therapy as a structured medical intervention began to take shape in the 1960s when American psychologist Boris Levinson noted that his dog Jingles had a remarkable calming effect on a withdrawn, non-verbal child patient. What followed were decades of incremental, sometimes sceptical, scientific inquiry — and eventually an accumulation of evidence robust enough to convince major healthcare institutions that animals belong in the therapeutic toolkit.

Today, AAT is deployed in diverse clinical contexts: reducing pre-operative anxiety in surgical patients, supporting stroke rehabilitation, managing agitation in dementia wards, and providing emotional support to trauma survivors and veterans. Understanding why it works — and the extent of what the evidence really shows — is essential for anyone considering it as part of a care plan.

The Neurobiological Basis of the Human-Animal Bond

When a person interacts positively with an animal — stroking a dog, making eye contact, or simply sitting in a calm animal's presence — measurable physiological changes occur. Cortisol levels (the primary stress hormone) fall. Oxytocin — sometimes called the "bonding hormone" — rises. Heart rate and blood pressure decrease. These changes are not merely psychological; they are biochemical, occurring in both the human and the animal involved in the interaction.

Oxytocin is particularly significant. This neuropeptide plays a central role in social bonding, trust, and the attenuation of fear responses via the amygdala. When oxytocin rises, the threat-detection system in the brain partially deactivates, creating a physiological state more conducive to therapeutic engagement, emotional processing, and interpersonal trust-building. The presence of an animal — which triggers oxytocin release through non-verbal, tactile interaction — can create this state without requiring verbal communication, making AAT especially valuable for patients who struggle to engage through conventional talk therapy.

What the Research Shows

The evidence base for AAT has grown substantially over the past decade, though methodological limitations (small sample sizes, heterogeneous populations, difficulty blinding participants) mean that systematic reviews urge caution in overstating effects. A landmark systematic review by Kamioka et al. (PMID 28186512) examined 11 randomised controlled trials of AAT across diverse populations and found consistently positive effects on depression, anxiety, fatigue, and certain physical health outcomes. None of the studies found harm from well-conducted AAT.

A meta-analysis by Maujean et al. (PMID 27459963) specifically examined AAT outcomes for depression and anxiety, finding significant reductions across both dimensions compared to control groups receiving standard care alone. Effect sizes were moderate — meaningful but not transformative in isolation — which aligns with the clinical consensus that AAT works best as an adjunctive therapy integrated with, not substituted for, evidence-based psychological or pharmacological treatment.

The National Institutes of Health has funded a dedicated research programme into human-animal interaction, acknowledging that the field has moved beyond preliminary curiosity to warrant serious, longitudinal investigation. The Guardian has documented how AAT is being integrated into NHS mental health services in the UK, with early programme evaluations showing patient-reported improvements in mood, motivation, and social engagement.

AAT Across Clinical Populations

Dementia and cognitive decline. Dog-assisted interventions in residential care settings have been linked to reductions in agitation and resistiveness during personal care in dementia patients. Physical contact with a calm, trained therapy dog appears to reduce the "sundowning" phenomenon — the late-afternoon anxiety spike common in dementia — and can facilitate reminiscence and social communication in patients who have otherwise become withdrawn.

PTSD and trauma. Veterans and trauma survivors are among the most studied populations in AAT research. The non-judgmental, non-verbal nature of interaction with a dog removes some of the performance anxiety and shame that can impede engagement with human therapists. Service dogs for PTSD are a closely related — though distinct — modality, involving a dog trained to perform specific tasks (interrupting nightmares, performing room checks, providing grounding during flashbacks) rather than simply accompanying a therapist session.

Children and adolescents. School-based AAT programmes have shown reductions in anxiety and improved reading engagement in children with learning difficulties. Science Daily has reported on studies in which classroom-based animal interactions improved children's social skills and reduced stress biomarkers. Paediatric hospital programmes using therapy dogs consistently show reduced pain scores and reduced analgesic requirements in hospitalised children.

Older adults and social isolation. Loneliness is a significant determinant of health outcomes in older adults, linked to cognitive decline, cardiovascular risk, and all-cause mortality. Both companion animals and structured AAT visits from therapy animals have shown promise in reducing loneliness in care home residents and community-dwelling elderly people.

Which Animals Are Used in AAT?

Dogs are by far the most common AAT animals, largely because they are already socially integrated with humans, can be trained to remain calm in clinical environments, and are broadly accepted across cultures. However, AAT organisations also work with horses (equine-assisted therapy is a specialist field in its own right), cats, rabbits, guinea pigs, and — in some specialist settings — llamas, alpacas, and dolphins. Pet Partners, one of the world's largest therapy animal certification bodies, registers teams across multiple species and maintains a research library of AAT outcomes.

All therapy animals used in clinical settings must be health-screened, temperament-tested, and regularly assessed. The welfare of the animal is a critical ethical consideration — a stressed animal is both less effective therapeutically and potentially unsafe.

Natural Wellbeing Support for Your Own Pet

For pet owners who want to support their animals' own emotional wellbeing — particularly those whose dogs accompany therapy work or simply experience anxiety in daily life — natural supplementation has an evidence-informed role to play.

Does AAT Work for Everyone?

No. Allergies, phobias, cultural or religious considerations, and personal history (for example, a trauma survivor whose trauma is directly linked to an animal) can make AAT inappropriate or counterproductive for specific individuals. Any responsible AAT programme will screen participants for contraindications before beginning. Animal therapy is also not a substitute for evidence-based psychological treatment in conditions like severe major depressive disorder, psychosis, or acute suicidality.

Within those parameters, the growing evidence base suggests that for many people — across ages, diagnoses, and settings — the presence of a well-chosen, well-trained animal in a therapeutic context accelerates engagement, reduces distress, and improves outcomes in meaningful and measurable ways.