However, only around half of those who go to hospital after the incident get a specialist mental health assessment, as national guidelines stipulate they should, the data show.
This is of particular concern as episodes of self-harm precede death in one in every two cases of suicide, the researchers point out.
The researchers base their findings on reported cases of self-harm among people aged 15 and older at five general hospitals in the cities of Oxford, Manchester and Derby between 2000 and 2012. Read the full paper here.
Self-harm includes intentional injury and overdosing on prescription drugs.
Our finding that only a little over a half of individuals presenting to hospital after self-harm were offered psychosocial assessment and that individuals who self-injured were least likely to receive an assessment, coupled with the rise in self-injury as a method of self-harm, and the link between such methods and suicide, may have important implications for the management of self-harm in hospitals.
The three cities are all part of the Multicentre Study of Self Harm in England, which is co-ordinated by the Centre for Suicide Research at Oxford University. These cities are socially and economically diverse, so the study population is reasonably representative of urban patterns across the country.
During the 13-year study period, 84,378 episodes of self-harm involving 47,048 people were dealt with at the five hospitals. Well over half of these cases (58%) were among women.
Almost four out of 10 people were under 25, and nearly two thirds (62%) were under 35. Almost a third (30%) were in receipt of some form of psychiatric care when they self-harmed.
Overall since 2000, rates of self-harm fell among women. They also fell in men, but only until 2008, after which they steadily rose, possibly because of the effects of economic downturn, suggest the researchers.
The rates of self-harm closely mirrored patterns of suicide seen in the general population, for both men and women.
More than three quarters of the episodes were caused by intentional overdose. Of these, common painkillers were used in over half the overdoses, while antidepressants were used in one in four (just under 25%).
Benzodiazepines, a class of drugs used to treat anxiety and sleep problems, were used in around one in seven cases (just under 14%), while major tranquilisers and antipsychotics were used in around 7% of cases.
A sharp increase in reported cases of cutting/stabbings and hanging/strangulation occurred in the second half of the study period.
“It should be noted that there is a stronger risk of suicide following self-cutting compared to self-poisoning,” write the researchers, adding: “Also repetition of self-harm is more common in individuals who cut themselves.”
One in four people self-harmed again within a year.
Overall, the proportion of people getting a specialist mental health assessment following their visit to hospital was greater in 2012 than in 2003, although this varied among the five hospitals.
Nevertheless, only just over half (53%) of 67,653 episodes of self-harm were followed up with a mental health assessment, as recommended by the National Institute of Health and Care Excellence (NICE) in 2004.
This was particularly true of people who cut themselves, with only just over a third (38%) of those who chose this method receiving an assessment, compared with more than 56% of those who overdosed.