Scientists have uncovered an unlikely key to happiness: more cats! In a new study, researchers investigated the relationship between wealth, cat numbers, and the prevalence of Toxoplasma gondii, a common parasite carried by felines. Analysis, published in the journal Plos One, revealed that countries with more cats per person had higher levels of happiness.

And one explanation could be that cats provide companionship and emotional support, making people happier overall.

Co-author Dr Indrikis Krams, of the University of Latvia, told the Daily Mail: 'Our study found that countries with more cats per 10,000 inhabitants tended to have higher levels of reported happiness. 'The association was quite strong, and cat density remained positively associated with national happiness even when several other variables were considered in our statistical model.'

A new study shows that the more cats per person a country has, the happier its population tends to be (illustrated) Economists have long documented strong correlations between national happiness levels and socioeconomic factors such as income, Gross Domestic Product (GDP), and medical spending. To see if other, more complex, factors could also be at play, the researchers decided to look at the possible impacts that cat ownership might be having.

The researchers gathered national data from 93 countries, including the UK, US, Australia, Canada, China and Russia. They discovered a 'strong' association between the number of cats per 10,000 inhabitants and levels of reported happiness. One possible explanation is that cats provide social and emotional benefits that increase happiness at the national level, they said. For example, previous studies have demonstrated that pets reduce loneliness, offer companionship, reduce stress and improve mood.

However, it might also be the case that cat density is simply an indicator of other factors that really lead to increased happiness.

On the other hand, researchers found that higher exposure to Toxoplasma gondii, a common parasite spread by cats (labelled IgM), leads to lower levels of happiness 'Societies in which people have the resources and living conditions that allow them to keep companion animals may already have characteristics associated with greater well-being,' says Dr Krams.

'Therefore, cats may contribute to happiness, but cat density may also partly be an indicator of broader social and economic conditions. Our study cannot distinguish between these possibilities.' However, the researchers' analysis also revealed a very important catch.

While cat levels were associated with increased happiness, countries with higher exposure to the parasites they carry were sadder overall.

Toxoplasma gondii is an exceptionally common parasite, and about 10 to 30 per cent of the global population are infected without knowing it.

However, cats are the only species in which the parasite can complete its lifecycle, and the infection is most commonly spread through their faeces.

The researchers discovered that the more people in a country were infected by the parasite, the lower the national level of happiness became.

While this doesn't prove that Toxoplasma gondii causes unhappiness, the researchers suggest that there could be a biological mechanism working behind the scenes.

Dr Krams says: 'Previous research has linked T. gondii infection with changes in mood, cognition and behaviour, and with several neuropsychiatric conditions.' A growing body of research suggests that latent infection could be associated with the development of conditions including schizophrenia, obsessive-compulsive disorder, autism spectrum disorders, anxiety disorders, depression, and personality disorders.

'Possible mechanisms include immune and inflammatory responses and effects on neurotransmitter systems and neural circuits involved in mood and emotional regulation,' says Dr Krams.

Scientists think that cats could improve happiness by alleviating loneliness, reducing stress, and improving mood. However, their study cannot show whether this is a case of causation or correlation (stock image) Surprisingly, the research also found that countries with more cats didn't have higher levels of parasite infections. In fact, cat density was associated with lower overall rates of Toxoplasma gondii exposure.

The researchers suggest this may be because countries with higher cat density tend to be wealthier than those with fewer cats per capita.

Co-author Dr Markus Rantala, of the University of Turku, told the Daily Mail: 'Our study suggests that this apparent paradox may be explained by differences in how cats are kept.

'In wealthier countries, where cat density tends to be high, cats are more likely to live indoors, eat commercially prepared food, and receive veterinary care. These conditions reduce their chances of becoming infected and shedding T. gondii oocysts.' This suggests that the most important factor may be the way that cats are kept, rather than the sheer number of felines on the streets.