A pet cat could double your chances of schizophrenia

But don't panic yet.

Having a pet cat could potentially double your risk of developing schizophrenia, according to a new study. 

Researchers from the University of Queensland, Australia, conducted a review looking at 17 studies from 11 countries including the US and the UK over the past 44 years. 

They found those who were exposed to cats before the age of 25 were around twice as likely to develop schizophrenia. 

Lead author Dr John McGrath said: ‘We found an association between broadly defined cat ownership and increased odds of developing schizophrenia-related disorders.’

In 1995, a paper proposed that some cases of schizophrenia may be caused by viruses that come from house cat, through the parasite Toxoplasma gondii, which can enter the body via a bite. 

The parasite can enter the central nervous system and affect neurotransmitters in the brain, leading to personality changes, psychotic symptoms and psychiatric disorders such as schizophrenia. 

However, the authors said that further research was needed to confirm the potential relationship, and since then, not all studies have found the association.  

But the team behind the latest meta-analysis – an overview of several studies – found ‘a significant positive association between broadly defined cat ownership and an increased risk of schizophrenia-related disorders.’

They wrote: ‘After adjusting for covariates, we found that individuals exposed to cats had approximately twice the odds of developing schizophrenia.’

However, it is important to note that the findings across the studies were inconsistent, and 15 of the 17 case studies used were case-control, which cannot determine a cause and effect as it does not look at external factors. 

For example, one study in the US looked at 354 students and found no association between cat ownership and scores on a schizotypy scale – a questionnaire that helps diagnose schizophrenia.

It did find, however, when comparing those bitten by a cat to those not bitten, the bitten subgroup had higher scores on the scale.

Schizophrenia symptoms typically begin between in mid-to-late 20s, but can start later. It is described as a type of psychosis, and does not usually cause someone to be violent.

The cause of schizophrenia is not well understood and is believed to be a mix of genetics, abnormalities in brain chemistry and/or possible viral infections and immune disorders. 

The researchers suggest that further research is needed before any firm interpretations can be made. 

‘In conclusion, our review provides support for an association between cat ownership and schizophrenia-related disorders,’ they said.

‘There is a need for more high-quality studies, based on large, representative samples to better understand cat ownership as a candidate risk-modifying factor for mental disorders.’

The study was published in Schizophrenia Bulletin.