October 6, 2025, 3:14 pm | Read time: 5 minutes
Dogs are sensitive and perceptive—but what happens when a puppy experiences trauma? A new study shows that a single stressful event in the first months of life can permanently alter later behavior. The effects of trauma in puppies range from fear to aggression—and can resonate throughout a dog’s life.
If dog owners agree on one thing, it’s that dogs are very sensitive, attentive, and perceptive. Every dog has its own character, which develops over their young life. Like humans, dogs can also experience traumatic events. Such traumas in puppyhood can have severe consequences, as a study by a research group shows.
What Are the Effects of Trauma During Puppyhood?
Fear and aggression are among the most common behavioral problems in dogs. For dog owners and their four-legged friends, this is often a significant burden and challenge. Previous studies showed that mistreatment negatively affects later behavior. However, these studies had gaps: The researchers mainly focused on working dogs or animals from rescue operations. More common stressors, such as early separation from the mother or general shelter stays, were often left unaddressed.
This is where the research group’s study comes in. The researchers suspected that stressful events in the first six months of life significantly increase the risk of fear and aggression. Additionally, there might be differences in the effects among different breeds. 1
Also interesting: Recognizing and Treating Trauma in Dogs
Study Examined Seven Clearly Defined Forms of Stress
The researchers randomly examined 4,497 dogs with an average age of 5.43 years. The owners reported on their dogs’ life events. The study specifically asked about seven clearly defined forms of stress:
- physical punishment,
- separation from a caregiver,
- physical abuse,
- attack by another animal,
- severe fright,
- serious injury,
- prolonged tethering or chaining outdoors.
Behavior was assessed using the standardized C-BARQ (Canine Behavioral Assessment & Research Questionnaire), an internationally recognized questionnaire that allows dog owners and professionals to systematically evaluate dog behavior and potential behavioral problems. Developed in 2003, it is now a reliable research tool worldwide for assessing fear, aggression, and other behavioral traits in dogs.
The researchers only counted early-life stress if it occurred within the first six months and was clearly confirmed. Additionally, data on age, weight, gender, origin, living conditions, and breed were collected. The results were statistically analyzed for differences between dogs with and without early-life stress. They also analyzed whether the effects varied by breed.
Shelter Dogs Had Higher Levels of Fear and Aggression
The study’s results are remarkable. Dogs that experienced stressful events in the first six months showed significantly higher levels of fear and aggression in adulthood than dogs without such experiences. The differences were highly significant and stronger than the effects of gender, neutering, or living with other dogs. The impact was particularly high for stressful events before the age of six months—during the sensitive phase of socialization.
Another important factor was the dog’s origin. Animals not directly from a breeder, but from shelters, foster organizations, or private surrenders, showed significantly higher average levels of fear and aggression than dogs from breeding operations. In the statistical analyses, acquisition from a shelter or similar source was one of the strongest predictors of noticeable behavior. This suggests that many of these dogs have already experienced changing environments or loss early on—stresses that can have long-term effects.
Certain Breeds Particularly Sensitive to Trauma
Another intriguing observation by the researchers concerned the influence of breed. In certain breeds, such as the Siberian Husky or the American Leopard Hound, the difference between stressed and unstressed dogs was particularly pronounced.
Other breeds, such as Labrador and Golden Retriever, showed notable resilience: Early stress had little effect on fear or aggression. These breed-specific differences suggest that genetic factors may influence susceptibility or resilience to stress—a key example of the interplay between genetics and environment in dogs.
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Trauma Primarily Affects Dogs in the First Months
The study demonstrates that traumatic experiences during puppyhood have profound effects on dog behavior. It confirms that the first months of life, especially the socialization phase (weeks 3–12), are a sensitive developmental period where negative experiences leave lasting marks.
The researchers conclude that dog behavior results from an interplay of genetic predisposition and environment: They describe it as so-called gene-environment interactions.
Additionally, the study provides important practical insights: Dogs from stressful backgrounds require particularly attentive care and possibly professional support to prevent or counteract behavioral problems.
However, the study also has a gap, as it is based on self-reports from dog owners. This can lead to biases, as it is ultimately subjective or incomplete knowledge about the dog’s history. To counteract this, the researchers only included clearly confirmed and dated results in the main analysis.
Conclusion: Time Before the Sixth Month is Crucial
Early-life stresses such as abuse, separation, or injuries significantly increase the risk of fear and aggressive behavior later in life. The time before the sixth month is particularly crucial. Origin also played an important role: Dogs from shelters or foster homes showed higher average levels of fear and aggression than dogs directly from breeders.
However, the authors emphasize that this does not argue against adoptions. Rather, the results highlight that dogs with unclear histories need special support and a stable environment to overcome stressful experiences. Overall, the study shows that behavior results from a close interplay of experience, environment, and genetics—and that early, positive care remains crucial for the well-being of dogs.