Research on 47,000 dogs reveals encouraging long-term behavioural changes
In the largest study of its kind, researchers analysing data from nearly 50,000 dogs have uncovered a surprising trend: cannabidiol (CBD) supplements may gradually reduce aggressive behaviour in dogs, though many questions remain about how and why this occurs.
The groundbreaking research, published in Frontiers in Veterinary Science, drew on information from the Dog Ageing Project- a long-term community science initiative tracking the health, lifestyle, and behaviour of companion dogs across the United States. The findings offer the first large-scale glimpse into which dogs receive CBD, why owners choose to give it, and what behavioural changes may follow.
A massive dataset that reveals clear patterns
Between 2019 and 2023, researchers collected annual survey data from owners of 47,355 dogs, making this the most extensive investigation of CBD use in pet dogs to date. The data revealed that 7.3% of companion dogs in the United States have been given CBD or hemp products, with 5.8% classified as frequent users receiving supplements daily.
Dr Maxwell Leung, senior author and assistant professor at Arizona State University, where he directs the Cannabis Analytics, Safety and Health Initiative, led the research team. “Behaviourally, dogs given CBD products for multiple years are initially more aggressive compared to dogs not receiving those products, but their aggression becomes less intense over time,” Leung explained.
Who receives CBD and why?
The study identified clear demographic and health patterns amongst dogs receiving CBD supplements. Age proved significant: dogs given CBD were, on average, three years older than those not receiving the supplements.
Health conditions showed even stronger associations. Dogs with dementia were most likely to receive CBD, with 18.2% of affected dogs given the supplement. This was followed by dogs with osteoarthritis and joint problems (12.5%) and those diagnosed with cancer (10%).
Geography also played a role. Dogs living in US states where human medical cannabis is legal were more likely to receive CBD, suggesting that owners’ attitudes towards cannabis influence their decisions for their pets. The research also found that male dogs had a 9% higher likelihood of receiving CBD than female dogs, though activity levels showed no significant difference between CBD users and non-users.
The aggression puzzle – surprising results
The most striking finding concerned behavioural changes, particularly around aggression. Dogs receiving CBD for extended periods were described by their owners as having lower-than-average aggression levels compared to dogs with no CBD use. This pattern emerged gradually over time, suggesting a cumulative calming effect.
However, the results also revealed a puzzling selectivity: whilst aggression decreased, other anxiety-related behaviours—such as general agitation or anxious responses—showed no similar improvement.
Dr Julia Albright, co-author and associate professor at the College of Veterinary Medicine at the University of Tennessee, offered insight into this paradox. “Most canine aggression is related to underlying stress or anxiety – a fight or flight response that kicks in. It is unclear why only aggression, but not other types of anxious or agitated behaviours, seemed to be improved with CBD treatment.”
This specificity raises important questions about CBD’s mechanism of action in dogs and whether the observed changes reflect direct neurological effects or other factors that remain unexplained.
What the study couldn’t answer
Despite its impressive scale, the research team acknowledged significant limitations in their findings. The study relied entirely on owner-reported data, which introduces the possibility of reporting bias. Owners who believe CBD is helping their dogs may unconsciously perceive behavioural improvements that other observers might not notice.
More critically, the dataset lacked crucial details about CBD administration – information about dosage, product formulations, delivery methods, and sources of CBD products was not systematically collected. “At this point, we do not have a complete picture about the behavioural treatment plan,” Albright noted.
The research also didn’t explore the biological mechanisms behind the observed behavioural shifts. Understanding why CBD might reduce aggression, whether through direct neurological effects, pain relief, or other pathways, will require controlled experimental studies rather than observational data.
Safety considerations
For owners considering CBD for their dogs, the researchers emphasised the importance of proceeding carefully. Albright and Leung stressed that owners should purchase reliable, quality-tested products and exercise caution with dosing.
CBD can cause side effects in dogs, most commonly gastrointestinal upset and diarrhoea. Without standardised dosing guidelines specific to individual dogs’ weights, breeds, and conditions, owners risk either underdosing (receiving no benefit) or overdosing (causing adverse effects).
The lack of regulatory oversight in the CBD pet product market compounds these concerns. Unlike prescription medications, CBD supplements vary widely in concentration, purity, and additional ingredients, making it difficult for owners to know precisely what they’re giving their dogs.
A framework for future research
Despite these limitations, the study provides a valuable framework for understanding CBD use in ageing and ailing dogs – a population that may benefit most from effective pain management and behavioural support.
“There are many similarities in how CBD can benefit dogs and humans medically,” Leung concluded, pointing to the potential for comparative research that could advance both veterinary and human medicine.
The overlap is particularly relevant for conditions common to both species: chronic pain, inflammation, anxiety disorders, and age-related cognitive decline. Dogs experiencing these conditions may serve as natural research models, potentially accelerating our understanding of CBD’s therapeutic potential whilst simultaneously improving canine welfare.
The road ahead
The researchers have called for controlled clinical trials to confirm CBD’s effects on canine aggression and to establish safe, effective dosing protocols. Such trials would need to include:
- Standardised CBD products with known concentrations
- Placebo controls to account for owner expectations
- Objective behavioural assessments by trained observers
- Biological measurements to understand mechanisms of action
- Long-term follow-up to assess sustained effects and safety
Until such evidence emerges, the current study serves as a starting point – identifying patterns that warrant further investigation whilst highlighting the gaps in our understanding.
Practical implications
For veterinary professionals and dog owners, this research underscores both the potential and the uncertainty surrounding CBD use in companion animals. The finding that aggression may decrease over time with CBD use is intriguing, particularly for dogs whose aggressive behaviour stems from pain or age-related changes.
However, the absence of controlled data means that CBD cannot yet be recommended as a proven treatment for canine behavioural issues. Owners concerned about aggression in their dogs should continue to work with veterinary behaviourists and trainers who can provide evidence-based interventions.
The study does confirm that many owners are already using CBD, particularly for older dogs with chronic health conditions, making it crucial that the veterinary community develop evidence-based guidance rather than leaving owners to navigate the unregulated supplement market alone.
A new chapter in canine wellness research
As CBD products continue to proliferate in the pet market, research like this Dog Ageing Project analysis becomes increasingly important. By documenting real-world usage patterns and observing long-term outcomes in thousands of dogs, scientists can identify which questions most urgently need controlled experimental investigation.
For a compound that has generated enormous interest but limited rigorous study in veterinary medicine, this represents meaningful progress, not because it provides definitive answers, but because it asks better questions and points towards the research needed to answer them properly.
The path from observation to evidence-based recommendation is long, but with nearly 50,000 dogs contributing data, researchers have taken a significant first step towards understanding whether CBD has a genuine role to play in canine behavioural health.
Study details:
- Published: Frontiers in Veterinary Science, November 2025
- Sample Size: 47,355 dogs
- Data Collection: Annual surveys, 2019-2023
- Source: Dog Ageing Project community science initiative
- Lead Researchers: Dr Maxwell C.K. Leung (Arizona State University), Dr Julia D. Albright (University of Tennessee)
- Key Finding: 7.3% of US companion dogs have been given CBD/hemp products; long-term use is associated with reduced aggression but not other anxiety behaviours.
Reference: Conrow, K.D., et al. (2025). Demographic features, health status, and behavioural changes associated with cannabidiol use in the Dog Aging Project. Frontiers in Veterinary Science, 12. DOI: 10.3389/fvets.2025.1666663
