A parasite spread by cats that is carried by two billion people may lead to schizophrenia, experts have warned.
Toxoplasma gondii (T. gondii) can be spread either through contract with cat litter trays or by eating uncooked meat but it is typically harmless.
However, according to a new study, the parasite could increase the chances of developing schizophrenia by 50 per cent.
Scientists at the Copenhagen University analysed data from more than 80,000 individuals in the Danish Blood Donor Study. Of these, 2,591 had registered psychiatric conditions.
The researchers, led by Dr Kristoffer Solvsten Burgdorf, looked through traces of immunoglobulin antibodies for T. gondii.
Shockingly, the parasite was found in the blood of a quarter of the population studied by the team.
They also found that 61 per cent of people carried cytomegalovirus (CMV), which has also shown evidence of cognitive impairment.
The results showed that patients infected with T. gondii were almost 50 per cent more likely to have been diagnosed with schizophrenia.
This led researchers to conclude that ‘Toxplasma has a positive effect on the rate of schizophrenia’.
Dr Burgdorf and his research team added: ‘T.gondii infection might be a contributing causal factor for schizophrenia.’
There was no other link between the parasite and any other psychiatric condition, the study found.
However, the researchers did stress that T.gondii could disrupt the action of an amino acid called tryptophan, which could potentially mean that by blocking it, a person would not feel the positive effects of serotonin.
The authors added: ‘Tryptophan is also the essential precursor of serotonin, which is involved in depressive disorders.’