How Early Trauma Shapes Dog Behaviour

Many of us are dog rescuers and we desperately want to help our dogs feel safe in their new and secure lives, yet it might be harder for our rescued dogs to feel safe than we think!

As a trauma specialist and dog advocate I welcome the recent study on puppyhood trauma and how it affects dogs throughout their lives.

It makes perfect sense that puppyhood affects how a dog copes with the World for the rest of their life, considering people struggle for generations from childhood trauma and we all share the same mammalian nervous system.

A recent study from Harvard University has provided the most comprehensive look yet at how early life experiences shape aggression and fear in dogs. Published in Scientific Reports this October, the research analysed nearly 4,500 dogs and uncovered undeniable parallels between trauma's effects on dogs and humans.

The research team, led by Julia Espinosa from Harvard's Department of Human Evolutionary Biology, found that adverse experiences during a puppy's first six months of life, including abuse, neglect, attacks by other animals, or abandonment, were strongly linked to increased aggression and fearfulness in adulthood.

Much like human infants, puppies undergo rapid neurological and social development during their early months.

The study identified this period as a critical window when the developing brain is particularly vulnerable to stress. Dogs who experienced trauma before six months old showed significantly higher levels of both aggressive and fearful behaviours compared to those who faced adversity later in life or not at all.

Perhaps the most interesting finding is that trauma's impact varies dramatically by breed. American Eskimo Dogs, American Leopard Hounds, and Siberian Huskies showed the strongest increases in problematic behaviours following early adversity. Meanwhile, Labrador Retrievers, known for their stable temperaments, showed relatively little behavioural change even after traumatic experiences.

This suggests that genetics and environment interact in complex ways to shape behaviour. Some breeds may carry genetic factors that make them more resilient to stress, whilst others might be particularly vulnerable. The researchers propose this could relate to what different breeds were originally selected for: dogs bred for guarding or hunting large game showed different response patterns than those bred primarily as companions.

The study's massive scale, involving 4,497 dogs across 211 breeds, provides unprecedented statistical power to understand these relationships. Guardian-reported data revealed that adverse events ranged from physical abuse and harsh training methods to experiences like living on the streets or being attacked by other animals.

One particularly heartbreaking case involved a Golden Retriever puppy who was severely underfed, weighing only 20 pounds at six months old. Whilst his body eventually recovered with proper care, he remained unusually fearful throughout his life, a reminder that emotional scars can persist long after physical wounds heal.

When we rescue a dog with an unknown history it can be tempting to believe that if they are safe then they will feel safe. It's not as straightforward as that though. This knowledge isn't a reason not to rescue though - not a bit - this awareness gives us the tools to understand and therefore empower our rescue dogs! 

1. Early intervention matters: Dogs with known trauma histories may benefit from professional behavioural support, particularly if the trauma occurred during puppyhood.
   
   
2. Breed considerations: When adopting a dog with an unknown or troubled past, understanding breed-specific vulnerability to stress can help set realistic expectations and inform training approaches.
   
   
3. Prevention is key: The findings underscore the importance of ensuring puppies receive proper care, socialisation, and positive experiences during their first six months.
   
   
4. Hope for recovery: Whilst early trauma has lasting effects, many dogs can still live happy lives with understanding guardians and appropriate support.

This research contributes to our growing understanding of how adverse childhood experiences affect mammals broadly. The parallels between dogs and humans are particularly striking: both species show that early trauma can have lifelong behavioural consequences, with the severity depending on both genetic factors and the timing of the adverse experiences.

As Erin Hecht, the study's senior author, noted: 

"Maybe this makes them a little bit more like us than we realised."

The study also highlights dogs' unique position as a model for understanding trauma and resilience. Because dogs share our environments and social structures whilst having much shorter lifespans than humans, they offer researchers a valuable window into how genes and environment interact to shape behaviour.

Whilst this research paints a sobering picture of trauma's lasting effects, it also points towards solutions. By identifying which dogs are most at risk and when they're most vulnerable, we can develop targeted interventions to prevent behavioural problems before they develop.

For the millions of dogs in shelters and rescue organisations, this research could inform better matching between dogs and families, more effective rehabilitation programmes, and ultimately, fewer dogs being returned or euthanised due to behavioural issues.

The Harvard team plans to continue following these dogs as they age, tracking how behaviour and health intersect over time. Their work reminds us that our dogs carry their histories with them, and that understanding those histories is the first step towards helping them heal and finally feel safe! 

If you're living with behaviour problems including fear or reactivity, my bumper bundle of eBooks will help you truly understand your dog. 

The full study, "Influence of early life adversity and breed on aggression and fear in dogs," is available in Scientific Reports (2025).