Young girls who smoke may have an increased risk of suffering from severe period pain, research suggests.

Period pain, also known as dysmenorrhoea, affects most females at some stage of their lives, however at least one in four suffers severe pain. In the past, smoking has been suggested as a possible risk factor for severe period pain, however studies have so far proved inconclusive.

Australian researchers decided to look into this further. They followed the progress of 9,000 women who were taking part in an ongoing study on women's health.

Every three to four years between 2000 and 2012, the participants were asked about period pain and their smoking status, including what age they had begun smoking. Other relevant information was also gathered, such as details about their reproductive history, their weight and their lifestyle.

When the study began in 2000, the women were aged between 22 and 27 and one in four currently smoked. Among the smokers, 7% had begun smoking by the age of 13, while 14% had begun at the age of 14 or 15.

Some 8% had started smoking before their periods had begun.

Also at the start of the study, one in four said they experienced period pain every month - those who smoked were slightly more likely to experience monthly pain compared to non-smokers.

The women were split into four groups depending on the level of pain they had:
-Normative (42%) had little or no pain
-Late onset (11%) experienced an increasing prevalence of pain over time
-Recovering (33%) experienced a decreasing prevalence of pain over time
-Chronic (14%) experienced a lot of pain throughout the monitoring period.

The study found that those who had started smoking by the age of 13 were much more likely to belong to the chronic group, as were women who were obese, unemployed or had started their periods early.

After taking into account all of the risk factors, the researchers found that those who started smoking by the age of 13 were 60% more likely to have chronic period pain compared to non-smokers.

"Cigarette smoking is known to constrict arterial blood flow, which could potentially cause pain. Alternatively, it might have a direct effect on the hormones involved in menstruation, which may be particularly important before the onset of puberty and regular monthly periods," the team from the University of Queensland suggested.

Details of these findings are published in the journal, Tobacco Control.