When we think about the harms of smoking, we often focus on its direct health consequences in humans: namely lung cancer, cardiovascular disease, and respiratory illness, among others. What often goes unnoticed is the impact cigarette smoke has on our closest companions: our pets.
For decades, experimental research has explored the physical effects of smoking on animals, particularly dogs, who were used as models to study human health risks. These studies have revealed lung damage, increased cancer susceptibility, and various other diseases in dogs subjected to smoke exposure. (Shout out to Brad Bolman’s recently-released book Lab Dog, which chronicles the use of beagles in laboratory experimentation; he has a chapter devoted to the cigarette smoke inhalation studies conducted on beagles.)
Yet a critical aspect remained largely ignored: how secondhand smoke affects dogs emotionally and behaviorally.
A new study by Alaie et al. (2025), “Behavioral changes in domestic dogs associated with exposure to secondhand smoke: A cross-sectional study,” has brought this overlooked issue to the forefront. The research, published in the Journal of Veterinary Behavior, found that dogs living with smoking owners exhibit notable behavioral changes compared to those in smoke-free homes. This study offers compelling evidence that secondhand smoke doesn’t just hurt a dog’s body—it alters their mind and behavior, too.
The Research: A Closer Look
The cross-sectional study examined 304 domestic dogs, evenly split between those exposed to secondhand smoke and those not exposed. Owners filled out detailed questionnaires assessing their dogs’ exposure levels and behavior, which was evaluated using the Dog Personality Questionnaire (DPQ). Variables such as sex, age, neutering status, and household dynamics were carefully considered.
The results were striking. Dogs exposed to cigarette smoke showed significantly higher odds of experiencing behavioral problems in six key areas:
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Fearfulness
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Reduced activity levels
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Aggression toward people
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Aggression toward other animals
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Decreased trainability
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Increased anxiety
These findings reveal that environmental tobacco smoke can deeply influence a dog’s emotional state and behavior, often in ways that are both troubling and dangerous.
Behavioral Effects and Their Consequences
Dogs who display aggression, anxiety, or fear are often perceived as problematic by their owners. These behavioral problems are one of the top reasons dogs are surrendered to shelters or even euthanized. According to studies by Dreschel (2010) and Segurson et al. (2005), around half of dog relinquishments are related to behavior issues. Thus, secondhand smoke may indirectly contribute to an increase in pet abandonment or shortened lifespans.
The heightened aggression noted in the study could put both humans and other pets at risk. Aggressive behavior toward other animals is especially concerning given that socialization is critical in multi-pet households or public settings like dog parks. Increased fearfulness and anxiety not only degrade the quality of life for the dog but also for the owner, who may struggle to manage such unpredictable behavior.
Moreover, reduced trainability means these dogs are less likely to learn commands or adjust to home routines. This further strains the human-animal bond and undermines one of the core benefits of dog ownership—companionship based on communication and mutual understanding.
Environmental Stressors and Canine Mental Health
Secondhand smoke contains thousands of chemicals, including known neurotoxins such as nicotine and carbon monoxide. In humans, exposure to these chemicals has been linked to mood disorders, including depression and anxiety. It’s reasonable to infer that similar mechanisms might be affecting dogs, whose neurophysiology shares many parallels with our own.
Unlike most humans, domestic dogs are rarely able to remove themselves from harmful environments. They can’t open a window, step outside for fresh air, or request a smoke-free space. They rely entirely on their owners for environmental safety. As a result, their prolonged exposure to environmental stressors like cigarette smoke can trigger chronic stress responses—altering their behavior, hormone levels, and ultimately, their mental and physical health.
The Human Factor: Owner Behavior Shapes Pet Behavior
Interestingly, behavioral changes in dogs are often reflections of their environment, including the habits and lifestyle of their owners. Numerous studies have established links between the emotional states and behaviors of dog owners and their pets. An owner who smokes might also engage in other lifestyle factors—such as higher stress levels, irregular routines, or reduced physical activity—that indirectly affect the dog.
Furthermore, smoking inside a home may signal a broader pattern of indoor environmental neglect. This is important to consider because dogs are sensitive to changes in their environment. Poor air quality, reduced social interaction, and limited physical stimulation can all impact a dog’s behavior.
Why Awareness Matters
The implications of the Alaie et al. (2025) study are clear: exposure to secondhand smoke poses serious risks to the behavioral health of dogs. Pet owners who smoke indoors may unintentionally contribute to aggression, fear, anxiety, and disobedience in their pets. These behaviors can escalate into severe issues, placing strain on the human-animal bond and increasing the likelihood of relinquishment.
Veterinarians and animal behaviorists should begin screening for smoking habits during consultations, especially when evaluating dogs for behavioral issues. Public health campaigns targeting smoking cessation should also consider including messages about pet health, broadening the scope of awareness beyond human health alone.
Final Thoughts
Dogs are more than just pets—they are family. They rely on us not just for food and shelter, but also for a safe, nurturing environment. The evidence is mounting that secondhand smoke undermines their behavioral well-being and overall quality of life. As we continue to better understand the mental and emotional lives of animals, it’s imperative that we make lifestyle changes that reflect this understanding.
So, if you’re a dog owner who smokes, the message is simple: smoke outside, or better yet, quit altogether—not just for your health, but for the health and happiness of your loyal companion
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