Researchers have discovered a possible link between family genetics and the underlying cause of cerebral palsy.

A new study conducted by Norwegian researchers investigated cerebral palsy over a broad range of family relationships, the first of its kind to include such a wide spectrum.

According to the Centers for Disease Control and Prevention (CDC), cerebral palsy is the most common cause of physical disability in childhood in the world, with over four per 1,000 live births resulting in the disease.

Until now, positive findings were difficult to duplicate in previous studies looking at family links to cerebral palsy. The researchers from Norway therefore decided to analyze the recurrence of cerebral palsy among family members, including twins, as well as first, second and third degree relatives in an effort to determine any possible patterns of inheritance.

Nearly two million single births and over 45,000 twins born in Norway between 1967 and 2002 were examined. They found that the prevalence of cerebral palsy was 1.8 per 1,000 born within this time period, with the rate being higher (5.1 per 1,000 live births) among twins.

Children were six to nine times more likely to have cerebral palsy in families where a single child was affected. Second degree relatives were up to three times more likely to be born with the disease.

“Our data suggest that cerebral palsy includes a genetic component, with a stronger recurrence among relatives with closer genetic relationship,” say the researchers, and that the underlying causes of the condition “extend beyond the clinical management of delivery,” said the researchers in a statement.