Background: The validity and reliability of suicide statistics have been questioned and few nationwide studies of deliberate selfharm have been presented. Aim: To calculate rates of deliberate self-harm in Denmark in order to investigate trends and assess the reliability of hospital records.

 Method: A register study based on all individuals recorded with an episode of deliberate self-harm or probable deliberate selfharm in nationwide registers during 1994-2011. 

Results: A substantial difference in the rates of deliberate self-harm and probable deliberate self-harm was noted for both genders. The average incidence rate of deliberate self-harm for women and men was 130.7 (95% CI = 129.6-131.8) per 100,000 and 86.9 (95% CI = 86.0-87.8) per 100,000, respectively. The rates of deliberate self-harm for women increased from 137.6 (95% CI = 132.9-142.3) per 100,000 in 1994 to 152.7 (95% CI = 147.8-157.5) in 2011. For a subgroup of younger women aged 15-24 years, an almost threefold increase was observed, IRR = 2.5 (95% CI = 2.4-2.7). The most frequently used method was self-poisoning. 

Conclusion: The rates of deliberate self-harm and probable deliberate self-harm differed significantly. An increased incidence of deliberate self-harm among young Danish women was observed, despite detection bias. An improved registration procedure of suicidal behavior is needed.