Children who take antibiotics may have an increased risk of developing juvenile arthritis.

Arthritis refers to an inflammation of the joints that causes pain and immobility. Juvenile arthritis (JA) refers to a number of forms of arthritis that begin in a child or young person before they are 16 years old. Around 1,000 children and teenagers in Ireland are currently living with the condition.

US researchers used a health database that held information on over 11 million people living in the UK. Using this, they were able to compare children with JA to children without the condition.

They found that children who had been prescribed antibiotics had twice the risk of developing JA compared to children who had not been prescribed these drugs.

Furthermore, the more courses of antibiotics a child took, the higher the risk of developing JA. This risk appeared to be strongest within 12 months of taking the antibiotics.

The researchers pointed to research that has shown that around one-quarter of antibiotics that are prescribed to children are probably not actually required.

"Our research suggests another possible reason to avoid antibiotic overuse for infections that would otherwise get better on their own," they said.

They also found that antiviral and antifungal drugs did not appear to increase the risk of JA, suggesting that the risk was specific to antibiotics.

However, the researchers also pointed out that children with JA have a higher risk of developing serious infections.

"So an alternative explanation to our findings is that this abnormal immune system makes children more susceptible to serious infection even before they are diagnosed with arthritis. Under this hypothesis, antibiotics would be a marker for abnormal immunity rather than a direct cause of arthritis.

"A majority of children get antibiotics, but only about 1 in 1,000 get arthritis. So even if antibiotics do contribute to the development of arthritis, it's clearly not the only factor," they said.

Details of these findings are published in the journal, Pediatrics.