- They analysed blood samples taken from 837 New Zealanders at the age of 38, as part of the Dunedin Longitudinal Study, which has been following the participants' physical and mental health since birth. Of these, 28 percent tested positive to Toxoplasma.
The team looked at four hypotheses, and came up with four conclusions:
1. Is T. gondii infection status related to neuropsychiatric conditions (schizophrenia and major depression)?
T. gondii infection was not significantly associated to either of these conditions.
2. Is T. gondii infection related to poor impulse control as reflected in four phenotypes: non-suicidal self-injury, suicide attempt, criminal convictions, and traffic-related offences and accidents?
While they found no association between non-suicidal self-injury, criminal convictions, and traffic-related offences and accidents suicide attempts were more common in T. gondii-positive people - but only very slightly.
3. Is T. gondii infection status related to personality differences?
"The personality profiles of individuals who tested positive for T. gondii antibodies were indistinguishable from the personality profiles of individuals who tested negative," they found.
4. Is T. gondii infection related to poorer neurocognitive performance?
T. gondii wasn’t correlated with IQ or other measures of cognitive performance except on one memory test, and again, only very slightly. "Associations between T. gondii infection status and all other tests of neurocognitive functions were not significant," the researchers report.