Many studies show that keeping cats and dogs has a positive impact on humans' physical and mental health and quality of life. The existence of this "pet phenomenon" is now widely discussed because other studies performed recently have demonstrated a negative impact of owning pets or no impact at all. The main problem of many studies was the autoselection-participants were informed about the aims of the study during recruitment and later likely described their health and wellbeing according to their personal beliefs and wishes, not according to their real status. To avoid this source of bias, we did not mention pets during participant recruitment and hid the pet-related questions among many hundreds of questions in an 80-minute Internet questionnaire. Results of our explorative study performed on a sample of 10,858 subjects showed that liking dogs has a weak positive association with quality of life. However, keeping pets, especially cats, and even more being injured by pets, were strongly negatively associated with many facets of quality of life. Our data also confirmed that infection by the cat parasite Toxoplasma had a very strong negative effect on quality of life, especially on mental health. However, the infection was not responsible for the observed negative effects of keeping pets, as these effects were much stronger in 1,527 Toxoplasma-free subjects than in the whole population. Any cross-sectional study cannot discriminate between a cause and an effect. However, because of the large and still growing popularity of keeping pets, the existence and nature of the reverse pet phenomenon deserve the outmost attention.

• MeSH
• Pets * MeSH
• Adult MeSH
• Internet MeSH
• Cats * microbiology   MeSH
• Quality of Life * MeSH
• Humans MeSH
• Mental Healing MeSH
• Human-Animal Bond MeSH
• Cross-Sectional Studies MeSH
• Surveys and Questionnaires MeSH
• Dogs * microbiology   MeSH
• Wounds and Injuries etiology   MeSH
• Toxoplasma MeSH
• Toxoplasmosis etiology   MeSH
• Animals MeSH
• Check Tag
• Adult MeSH
• Cats * microbiology   MeSH
• Humans MeSH
• Male MeSH
• Dogs * microbiology   MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Latent infection with Toxoplasma gondii has repeatedly been shown to be associated with behavioral changes that are commonly attributed to a presumed increase in dopaminergic signaling. Yet, virtually nothing is known about its effects on dopamine-driven reward processing. We therefore assessed behavior and event-related potentials in individuals with vs. without latent toxoplasmosis performing a rewarded control task. The data show that otherwise healthy young adults with latent toxoplasmosis show a greatly diminished response to monetary rewards as compared to their non-infected counterparts. While this selective effect eliminated a toxoplasmosis-induced speed advantage previously observed for non-rewarded behavior, Toxo-positive subjects could still be demonstrated to be superior to Toxo-negative subjects with respect to response accuracy. Event-related potential (ERP) and source localization analyses revealed that this advantage during rewarded behavior was based on increased allocation of processing resources reflected by larger visual late positive component (LPC) amplitudes and associated activity changes in the right temporo-parietal junction (BA40) and left auditory cortex (BA41). Taken together, individuals with latent toxoplasmosis show superior behavioral performance in challenging cognitive control situations but may at the same time have a reduced sensitivity towards motivational effects of rewards, which might be explained by the presumed increase in dopamine.

• MeSH
• Dopamine metabolism   MeSH
• Adult MeSH
• Evoked Potentials MeSH
• Cognition physiology   MeSH
• Humans MeSH
• Young Adult MeSH
• Reward * MeSH
• Antibodies, Protozoan metabolism   MeSH
• Auditory Cortex MeSH
• Case-Control Studies MeSH
• Toxoplasma immunology   MeSH
• Toxoplasmosis metabolism   psychology   MeSH
• Check Tag
• Adult MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Dopamine MeSH
• Antibodies, Protozoan MeSH