Does having a dog nearby soften the stress of a traumatic film?
Watching a distressing film with a friendly dog made women feel less anxious afterwards, as much as having a friendly person there, but did not change their bodily stress response.
Source
Presence of a dog reduces subjective but not physiological stress responses to an analog trauma
Study at a glance
- Design
- Human experiment — Between-subjects randomised experiment: participants watched an 11-minute violent 'trauma' film either with a trained therapy dog, a friendly unfamiliar woman, a life-size toy dog, or alone; self-report, cardiovascular and salivary cortisol measures taken before, during and after
- N
- N=77 · 80 women were randomised (20 per condition); 3 from the dog group were excluded, leaving 77 for analysis. A few further participants lacked physiological or cortisol data.
- Population
- Healthy female university students in Germany using oral contraceptives, without fear of dogs, prior trauma or psychiatric disorder
- Outcome
- Change in state anxiety (STAI-S) and positive/negative affect (PANAS) from before to after the film; heart rate, blood pressure and salivary cortisol responses
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What they did
Healthy female students were randomly assigned to watch an 11-minute compilation of violent and sexual-assault scenes from a feature film either with a trained therapy dog lying beside them, with a friendly unfamiliar female student, with a life-size toy dog, or alone. Before and after the film they rated state anxiety and positive and negative mood; heart rate and blood pressure were recorded before, during and after, and saliva was sampled six times over the following hour to measure cortisol.
What they found
The film raised anxiety, negative mood, heart rate, blood pressure and cortisol in every group. After the film, the dog group reported lower state anxiety and negative affect than the toy-dog and alone groups, and did not differ from the friendly-person group; the condition-by-time interaction for anxiety had a partial eta squared of about 0.115. Positive affect fell equally in all groups, and there were no group differences in heart rate, blood pressure or cortisol (the dog group's cortisol increase was numerically smallest but not significantly).
The limits
What it doesn't show
The sample was only young, healthy women, so it is unknown whether men or people with PTSD would respond similarly; the trauma film is an analogue, not a real traumatic event. Participants could not be blind to condition, so expectations or demand could have shaped the self-reports, and the dissociation between subjective and physiological measures means the dog did not measurably dampen the body's stress response. Groups differed at baseline in attitudes to pets (though in the direction that works against the dog effect), and intrusive memories after the film, the key PTSD-relevant outcome, were not measured.
Key terms
- Trauma-film paradigm
- An analogue method in which healthy volunteers watch a distressing film to study stress reactions and intrusive memories in the lab.
- State anxiety (STAI-S)
- How anxious a person feels right now, as opposed to trait anxiety, which is a stable tendency to feel anxious.
- Social buffering
- The reduction of stress responses by the presence or support of another person or animal.
- Cortisol
- A hormone released by the HPA axis in response to stress, measurable in saliva.
- Active control condition
- A comparison group that matches features of the treatment (here a toy dog) to rule out effects of having any companion object present.
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Common questions
Why include a toy dog group?
The toy dog controls for simply having a dog-shaped object and a short introduction beside you. Because the real dog lowered anxiety relative to the toy, the effect is not just about distraction by an object.
If cortisol and heart rate did not change, did the dog really reduce stress?
It reduced the experienced, self-reported part of stress. The body's arousal response to the film was the same in all groups, so the study shows a dissociation between subjective and physiological stress rather than a full stress reduction.
Does this prove PTSD service dogs work?
No. It tested healthy women watching a film, not PTSD patients facing reminders of real trauma, so it offers only preliminary support for the idea.
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