Has the number of teenage girls self-harming doubled? The number of hospital admissions in England for girls under the age of 18 because of self-harm has doubled in that time. The number of girls admitted to hospital because of self-harming has doubled in the last 20 yearsThe number of admissions for girls under the age of 18 because of self-harm increased from around 7,300 in 1997/98 to 13,500 in 2016/17. Over the same time period the number of girls in England under the age of 18 has increased by just 5%. The number of girls under the age of 18 increased more than tenfold between 1997/98 and 2016/17, from around 250 to 2,700.