This thesis presents three classes of mechanism that may explain reported associations between pet ownership and health benefits. The first suggests any association is noncausal.
Studies 1-3 examine candidate factors to explain both health advantages and likelihood of pet ownership. Type A behaviour was hypothesised to be associated with higher risk of illness and lower likelihood of pet ownership. Hardiness was hypothesised to be associated with better health and increased likelihood of pet ownership. Neither hypothesis was supported.
The second class of explanation suggests that pets indirectly effect health by acting as social facilitators of human-human interactions. Enhanced social contact may lead to health advantages. Studies 4-6 examine the robustness of the catalysis effect of Pets and its impact on owners' social networks. Whilst the catalysis effect was found to be robust in generating social contacts, these were superficial and not regarded as providing relationship functions likely to enhance health.
The third class of explanation suggests pets have direct effects on health through the nature of the relationship with the owner, or through physiological effects such as reduced cardiovascular arousal to stress. Study 7 indicates that pets serve valuable supportive functions for normal children. Study 8 found that young people with autism demonstrate positive behaviours within their relationships with pets which they do not with people. Study 9 found the relationships between people with physical disabilities and their service dogs serve many supportive, as well as instrumental, functions and that this is associated with better self-perceived health. Studies 10 and 11 found no evidence that pet presence moderates cardiovascular reactivity to a laboratory stress task.
Little evidence was found of an association between pet ownership and health advantages, although it is clear that pets can be significant and valued relationships for their owners.