Some care homes now welcome visiting therapy dogs, and a few have even hosted a pony. Residents often seem to brighten when a friendly animal walks in. Researchers have started to test whether that impression shows up in the numbers. The answer so far is encouraging, with an honest asterisk: the studies are small and imperfect, so we know the direction better than the size of the benefit.
The best single answer: a meta-analysis of 19 trials
A 2024 systematic review searched SCOPUS, Web of Science and PubMed for randomized trials in adults aged 65 or older. It found 23 studies, 19 of which could be pooled in a meta-analysis, and looked at depressive symptoms.
- Animal-assisted therapy (AAT): g = -0.72 (95% CI -1.13 to -0.31; p = 0.001), described by the authors as a moderate and statistically significant reduction in depressive symptoms. A negative value means fewer symptoms.
- Dog-assisted therapy, on its own: g = -0.65 (95% CI -1.21 to -0.08; p = 0.025), a more modest effect.
- Pet-robot interventions: no significant effect on depressive symptoms. In this analysis, the living animal seemed to matter.
The asterisk
Using the Cochrane RoB 2 tool, 78.9% of the studies (n = 15) were rated at high risk of bias. That is understandable, since nobody can be blinded to whether a dog is in the room, but it means the true effect is probably smaller than the headline number. The confidence intervals are also wide.
The Cochrane review of animal-assisted therapy in dementia points the same way, more cautiously. It pooled nine randomized trials with 305 participants, mostly with dogs and one with horses. Compared with no animal therapy, participants may have been slightly less depressed afterwards (mean difference -2.87, 95% CI -5.24 to -0.50; 2 studies, 83 participants), but the certainty of that evidence was low.
And the pony?
A 2024 systematic review of equine-assisted services for people living with dementia found only six studies and 44 participants with dementia. They reported favorable effects on neuropsychiatric symptoms, quality of life, well-being, social participation and communication. It is a promising but very small evidence base, and the authors call for more robust studies.
What might be happening in the body
A review of 69 human-animal interaction studies (published in 2012) reported well-documented benefits for mood, social behavior and stress-related measures such as cortisol, heart rate and blood pressure. Its authors proposed that the oxytocin system, linked to bonding and calm, plays a key role in many of these effects. That is a hypothesis backed by early findings, not settled fact.
A 2026 systematic review of 37 studies, mostly with dogs (22) and horses (15), examined whether the body signals of person and animal move in step, such as heart or hormone measures. Coupling was significant in 16 studies, partial in 16 and absent in 5. The authors call the evidence supportive but not conclusive, partly because the studies differ so much.
Our reading: the evidence is imperfect, but it lines up with what many care teams see. For an older person who likes animals, a regular visit is a low-cost, pleasant addition to care that may lift mood. It is not a replacement for treating depression, which still needs proper assessment and care.
This article is for general education and is not medical advice.