Toxoplasmosis, Behaviour & Schizophrenia

Animal studies have shown that long standing toxoplasma infection is associated with altered behaviour including increased movement in mice and diminished fear of novel scent, sound or sight in rats.⁽¹⁾  This altered behaviour may lead to enhanced feline predation, completing the life cycle of Toxoplasma gondii.

A series of studies of human personality found an association between males with long standing toxoplasma infection and less desirable behavioural patterns such as rule breaking, suspicious nature, jealousy, being dogmatic and suffering from feelings of guilt.  Infected females were more likely to feel adequate and to be self- sufficient compared to uninfected controls.  The degree of personality shift increased with the duration of toxoplasma infection suggesting infection influences personality and not vice-versa.⁽²⁾

Prenatal follow up studies in New England have found a significant association between the detection of toxoplasma specific IgM at the end of pregnancy and subsequent development of psychosis in offspring.  Patients with schizophrenia are more likely to have elevated levels of toxoplasma specific IgG than controls.  Whilst the exact role of toxoplasmosis in human psychiatric disease remains uncertain, a number of trials using standard neuroleptic therapy with or without anti-parasitic treatment for schizophrenia are now in progress.

(1) Holliman RE

Toxoplasmosis, Behaviour & Personality

J Infect, 1997; 35: 105-110

The strong view of the PHLS Toxoplasma Reference Unit is that routine testing based on psychiatric assessment alone, should not, at the present time, be considered as sufficient indication for undertaking serological investigation for toxoplasma infection.