Original ArticlesPsychophysiological Effects of Human-Animal Interaction: Theoretical Issues and Long-Term Interaction EffectsVirués-Ortega, Javier MS*†; Buela-Casal, Gualberto PhD†Author Information *Instituto de Salud Carlos III, Centro Nacional de Epidemiología, Madrid, Spain; and †Departamento de personalidad, evaluación y tratamiento psicológico, Universidad de Granada, Granada, Spain. Supported by the Andalusian Government's special grant for hospital research projects (Subvención de Junta de Andalucía a Proyectos de Investigación en Centros Sanitarios; BOJA 2/29/2002, p. 1302, exp. num. 111). Send reprint requests to Javier Virués-Ortega, Instituto de Salud Carlos III, Centro Nacional de Epidemiología, C/Sinesio Delgado, 6, 28029 Madrid, Spain. E-mail: firstname.lastname@example.org. The Journal of Nervous and Mental Disease: January 2006 - Volume 194 - Issue 1 - p 52-57 doi: 10.1097/01.nmd.0000195354.03653.63 Buy Metrics Abstract This paper reviews literature published on the psychophysiological effects of long-term human-animal interaction (i.e., pet ownership, pet adoption). A literature search was conducted using PsycInfo and Medline databases. Although the available evidence is far from being consistent, it can be concluded that, in some cases, long-term relationships with animals may moderate baseline physiological variables, particularly blood pressure. Results proved more coherent in studies where animals were adopted by owners as part of the procedure. This paper examines existing hypotheses seeking to account for these effects and the supporting evidence. Two major hypotheses have been suggested to explain the psychophysiological effects of long-term interaction, namely (1) stress-buffering effects of noncritical social support provided by pets; and (2) classical conditioning of relaxation. These mechanisms may partially account for the long-term health outcomes observed in a number of human-animal interaction studies. © 2006 Lippincott Williams & Wilkins, Inc.