Millions grow up with a cat, and consider their pet a cherished member of the family.
But now scientists have discovered evidence to suggest owning a feline as a child could increase a person's risk of developing mental health problems.
They believe a parasite that lives in cats could be linked to a greater risk of schizophrenia.
Their findings replicate those found in two other, past studies.
'Cat ownership in childhood has now been reported in three studies to be significantly more common in families in which the child is later diagnosed with schizophrenia or another serious mental illness,' the researchers wrote, according to Huffington Post Health.
The researchers looked at a questionnaire that had been distributed to families in 1982 but whose answers had not yet been analysed by scientists.
It included data on 2,125 families who belonged to the National Institute of Mental Illness (NAMI), and found 50.6 per cent who developed schizophrenia owned a cat in their childhood years.
The results were strikingly similar to two studies conducted among NAMI members in the 1990s.
These studies found a 50.9 per cent and 51.9 per cent of people with schizophrenia grew up with a cat, respectively.
The research shows a link rather than a cause and effect relationship, they said.
However, they theorised that the parasite toxoplasma gondii (T. gondii), which can be passed from cats to humans, could play a role in the development of schizophrenia.
'T. gondii gets into the brain and forms microscopic cysts,' Dr Edwin Torrey, of the Stanley Medical Research Institute told the Huffington Post.
'We think it then becomes activated in late adolescence and causes disease, probably by affecting the neurotransmitters.'
If a person is generally healthy, their immune system should keep the parasite in check.
They remain in the body in an inactive state, and makes re-infection less likely as the body builds up immunity.
But disease or certain medication can weaken the body's resistance, making re-infection more likely.
And T. gondii can also lead to miscarriages, fetal development disorders, blindness and even death.
The researchers suggested keeping cats indoors – as they could catch the parasite from a neighbor's cats.
They also suggested keeping litter boxes covered, since humans can catch it if they come into contact with cat faces.
The research was published in the journal Schizophrenia Research.
