Young teenage girls are three times as likely as boys to self-harm, an analysis of data from GP surgeries has revealed.

The number of girls aged between 13 and 16 who self-harm increased by 68% between 2011 and 2014, according to the analysis published in the BMJ.

The data, which was collected from 674 GP surgeries, showed nearly 17,000 cases of young people who reported self-harming between 2001 and 2014. Overall, there were three times the number of girls self-harming as boys, with the surge in the number of girls coming at the end of the 13-year period studied.

The rates of self-harm were significantly higher in deprived areas. However, the likelihood of being referred to a specialist mental health clinic was 23% lower in deprived areas compared with wealthier regions, the study found.

Children and teenagers who self-harmed were 9 times more likely to die than unaffected people. They had a significantly higher risk of suicide, as well as death by alcohol poisoning or drug overdose.

While the underlying causes of the increasing rates of self-harm among girls wasn't investigated in the study, the authors warned over the impact of stress.

"It is perhaps a reflection that today's early adolescents are living in more stressful times," said the authors, led by Cathy Morgan at the University of Manchester.

While digital media can improve young people's access to care, it also takes its toll. A state of "extreme connectedness" could be impairing young people's mental health and contributing to the rise in self-harm, they said.

"The reasons behind self-harm can be complex, but we know that teenage girls face a wide range of pressures, including school stress, body image issues, bullying and the pressure created by social media," said Tom Madders, director of campaigns at the charity YoungMinds.

The teenagers who talk to a doctor about self-harming could well be the minority, with many cases going unreported.

"It can take a lot of courage for a young person to tell their GP that they're self-harming, and it's crucial that specialist mental health services are available for all those who need support," Madders continued.

"As a society, we also need to do more to prevent mental health problems from developing in the first place."