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What We've Known

NSSI is a major public health concern worldwide.15 However, despite decades of research on NSSI, the epidemiology of these behaviors is still relatively unknown. Prevalence estimates of NSSI vary considerably across studies (e.g., 1-60%).2 The wide variation is likely due to selective sampling and inconsistent assessment techniques across studies. First, rates from most previous studies are based on small, convenient, and regionally based samples (e.g., upper-middle-class suburban adolescents). Second, research indicates that different measurement techniques yield disparate estimates of NSSI. For instance, studies using single-item measures consistently report lower rates than studies using NSSI behavior checklists.15 In addition, higher rates are reported in studies with broader definitions of NSSI and lower NSSI frequency thresholds16 compared to studies focusing only on moderate to severe NSSI behaviors (e.g., cutting) and requiring repetitive engagement in NSSI.17

What We've Learned

Over the past 5-7 years, the quality of prevalence studies has greatly improved with the use of larger and more representative samples and longitudinal designs. In order to provide the most accurate current prevalence estimates, when possible, the rates reported here are drawn from these recent large-scale studies. Data from North American community samples indicate that approximately 14-30% of adolescents,15,18 7-22% of young adults (aged 18-24),19,20 and 4-6% of adults21,22 report having engaged in NSSI at some point in their lifetime. Similar to lifetime estimates, rates of past-year NSSI also vary widely. Approximately 7-22% of adolescents,16,18 2-7% of young adults,19,20 and 1% of adults22 from community samples endorse past-year NSSI. Rates of NSSI in clinical samples are considerably higher than in community samples, but no less heterogeneous. Among individuals receiving mental health treatment, a history of NSSI is endorsed by approximately 37-68% of adolescents23,24 and 19-46% of adults.21,25 Cross-national rates are generally consistent with those observed in North American samples. Approximately 2-5% of adults from Great Britain26 and 9-36% of adolescents from Western Europe,17,27 Australia,28 and China29 endorse a lifetime history of NSSI. One recent study estimated the prevalence of NSSI disorder using the DSM-5 criteria in a large community sample of adolescents in Sweden: among the 35% of youth who engaged in past-year NSSI, approximately 7% met diagnostic criteria for NSSI disorder.17

The field lacks definitive data on differences in rates by gender and ethnicity. In terms of gender differences, the findings are mixed. Several recent studies suggest that, among community samples of adolescents and young adults, females are more likely to report a lifetime history of NSSI,18,19 whereas other studies report no gender differences.13,30 However, in clinical samples, females consistently report NSSI at higher rates than males.24,25 Evidence also is mixed with respect to ethnicity differences in rates of NSSI, with some studies reporting higher rates in Caucasian samples,30 whereas other studies report similar rates across ethnic groups.31

Although there is considerable variation in rates of NSSI across studies, a consistent finding is the significantly higher prevalence of NSSI among adolescents compared to adults. There are a few possible explanations for these age differences: rates of NSSI are increasing in recent years, adult reporting of NSSI is attenuated by forgetting or other reporting biases, or both.2,15 In light of methodological issues obscuring the true prevalence of NSSI (particularly among older studies), it is difficult to conclude at this time what might account for the higher rates of NSSI reported among younger samples. However, it is important to note that although rates among adolescents have increased in recent decades, it appears that NSSI rates stabilized in the period from 2005 to 2012.15

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