The current study reviewed the prevalence of DSM-5 eating disorders. A total of 19 studies were identified in our literature search, with results showing substantial variability in prevalence rates. A wide range of both point- and lifetime prevalence rates were reported across included studies, with variance being dependent on, first and foremost, the methodologies applied.
As intended, a number of studies now support the decline in EDNOS/OSFED prevalence following the DSM-5 diagnostic revision intention [10, 11]. Decreased EDNOS/OSFED prevalence has also been reported in studies having recoded ED diagnoses [9, 13, 20]. However, although the introduction of the new DSM-5 criteria appears to have resolved some of the challenges associated with EDNOS, OSFED still represents a heterogeneous group in the DSM-5, including a variety of different ED conditions. For example, PD, which has been shown to be associated with significant medical complications [25], was investigated specifically in three studies in our review [11, 14, 26]. Prevalence rates ranged from 0.58% (CI 0.42-0.80) – 3.77% (CI 3.14-4.49) with results illustrating a trend towards higher rates in females compared to males, as well as higher rates in adults compared to adolescents. However, it should be noted that lifetime prevalence rates as opposed to point prevalence rates, in general, is expected to be higher, especially when assessed in older populations. Night eating syndrome (NES) was also included in the DSM-5 OSFED category, and specifically assessed in two of the reviewed studies. [21, 22] Both adopted the self-report measure Night Eating Questionnaire (NEQ) [23]. Whereas de Zwaan and colleagues [23] reported a point prevalence of 1.1% among males and females aged 14-85 years (mean age 48), Runfola et al. [24] reported a prevalence of 4.2 among males and females aged 18-26 years (mean age 21). These discrepant findings in prevalence may relate to the differences in age between the two samples, but more research is warranted to investigate this further. Additionally, the new category Unspecified Feeding or Eating Disorder (UFED) was introduced in the DSM-5. UFED is used to describe symptoms characteristic of feeding or eating disorders causing significant stress or impairments in functioning, but without meeting full criteria for an ED diagnosis. The UFED category can be used when reasons for not meeting full criteria is lacking or not further specified by clinicians. Three of the included studies [10, 11, 15] reported prevalence of UFED, with rates ranging from 0.0% to 1.41%. Further research is needed to yield more information about the prevalence of PD, NES, and UFED.
After being included as an EDNOS in DSM-IV, BED was introduced as a specified and independent diagnostic category in DSM-5. Prevalence of BED was reported in several studies included in this review, and the prevalence of BED generally increased by increasing age in the reviewed studies. For example, Allen et al. [20] assessed BED among 1383 young Australian males and females at ages 14, 17, and 20. Point prevalence increased from 1.8% to 4.1% from age 14 to 20 (increase from 0.0% to 0.7% in males). Similarly, Stice et al. [17] investigated 496 young females (mean age 13 years at baseline), and reported a cumulative incidence of 2.7% and a lifetime prevalence at 3.0% by age 20. Finally, Trace et al. [6] assessed a larger and older sample of 13,295 females aged 20-47 years, with a reported lifetime prevalence of 5.8%. Prevalence of BED was generally higher among females than males across studies. A potential explanation for variability in BED prevalence rates is the inconsistent or lack of use of the DSM-5 marked distress criterion and binge eating specifiers such as guilt after binge eating [11].
Impact of the DSM-5 on prevalence estimates
It is of interest to review whether the transition from DSM-IV to DSM-5 has yielded the intended alterations in reported prevalence, i.e. increased prevalence of AN and BN, and decreased prevalence of the residual category EDNOS/OSFED. Several of the included studies in the present review have estimated prevalence of EDs as defined by both DSM-IV and DSM-5 in the same sample. Such recoding of diagnostic categories according to DSM-IV versus DSM-5 informs us on the impact of the DSM-5 on different ED prevalence rates. One study [7] assessed prevalence of AN by first adopting DSM-IV criteria. Subsequent to recoding according to the DSM-5 criteria, the authors observed a 60% increase in lifetime prevalence of AN among the 2825 female participants (mean age 24 years), from 2.2 to 3.6%. Another study recoding from DSM-IV to DSM-5 diagnoses investigated 1383 males (49%) and females at ages 14, 17, and 20 [20]. Significantly greater ED prevalence rates were reported when using DSM-5 criteria at all ages for females, and at age 17 only for males. These findings are in line with the study of Flament et al. [13] reporting that prevalence of full-threshold EDs increased from 1.8 to 3.7% after recoding from DSM-IV to DSM-5 criteria. Decreased prevalence of the residual ED categories (EDNOS/OSFED) when adopting DSM-5 criteria have also been reported across studies having recoded ED diagnoses [9, 13, 20]. It is worth noting that although research recoding ED prevalence from DSM-IV to DSM-5 has been important in the initial evaluation of the proposed DSM-5 criteria, these studies may have missed patients who initially did not qualify for an ED diagnoses based on DSM-IV, but who would have met criteria for a DSM-5 ED. This may imply a risk of inaccurate prevalence estimates in these studies.
A main intention of the DSM-IV revisions was to minimize the use of catch-all diagnoses such as Eating Disorders Not Otherwise Specified (EDNOS), the most frequently, reported ED diagnosis in the DSM-IV. However, the revisions made may not only contribute to altered rates of AN, BN and OSFED diagnoses, but may also increase the likelihood of reaching the threshold for a formal ED diagnosis. As the new OSFED category includes disorders which lack strict diagnostic criteria (e.g. PD and NES which lacks frequency criteria), clinicians and researchers should be vigilant with regards to the characteristics, especially significant distress and impairments, separating eating disturbances from eating disorders.
Methodological aspects
Methodological aspects are likely to influence both lifetime- and point prevalence rates including assessment measures adopted and samples investigated [3]. The majority of studies in this review adopted self-report to assign ED diagnoses, followed by interviews and 2-stage designs. Although self-report assessments have its obvious advantages in terms of being cost- and time effective, only diagnostic interviews can help determine the presence (or absence) of a formal ED diagnosis as defined by the DSM. Methodological issues such as these should be considered when interpreting prevalence rates across studies. In addition to assessment measure per se, recruitment strategy and design are important aspects to consider when evaluating quality of studies and consequently reliability of results. The 2-stage design, including stage one with screening followed by stage two with clinical diagnostic interview, have been considered the preferred approach to estimate prevalence rates. In the current study, aiming to review the prevalence of diagnosable EDs as defined by the diagnostic manual DSM-5, it may therefore be timely to consider the included 2-stage design studies [7, 9, 10, 15, 16] to be among the highest ranked studies in terms of quality. However, another marker of quality in epidemiological studies is sample size. The reviewed studies with the largest sample sizes include samples of N = 6041 [11], 13,295 [6], 10,038 [4], and 22,397 [27]. It is worth noting that none of these latter studies are among the mentioned 2-stage design studies, demonstrating the necessity to consider multiple methodological aspects when evaluating quality. In addition to the above-mentioned aspects, sample characteristics are likely to influence reported prevalence rates, and includes both age ranges and gender distributions. One of the intentions of the DSM-5 was to better capture EDs in males than during the DSM-IV era, and was a central rationale for removing the amenorrhea criteria for AN. However, as the DSM-5 revisions have contributed to higher prevalence of full-threshold AN and BN in general, it is difficult to detect whether the DSM-5 has led to better detection of male EDs per se. Also, although the amenorrhea criterion has been removed, the core ED psychopathology outlined in the DSM-5 is still biased towards females as it focuses on drive for thinness rather than muscularity. Furthermore, assessment measures used to detect ED psychopathology are often gender biased in that they have been developed to capture “female” psychopathology and symptoms, and also, as they most commonly are validated using female samples [28, 29]. Issues such as these may complicate the detection and description of ED pathology in males. Another methodological issue subsequent to the introduction of DSM-5 is the removal of a specific weight threshold for AN. This has clear advantages, maybe in particular in terms of individual and flexible evaluations in clinical settings, but it is worth noting that in research, the lack of an explicit weight criterion may lead to larger weight variations compared to earlier. In general, it is important to strive for consistent use of DSM-5 categories, which will aid the interpretation of prevalence rates across studies.
New diagnostic categories in the DSM-5 include ARFID (problem with eating not related to weight or shape concerns, leading to inability to take in adequate nutrition), pica (recurrent consumption of “nonnutritive, nonfood” items), and rumination disorder (RD; i.e. recurrent, effortless regurgitation of food). Although none of the included studies investigated these full-threshold diagnoses, three studies which were excluded due to their sub-threshold nature, addressed features of ARFID [30], pica and RD [31], reporting frequency numbers ranging from 0 to 3.2%. More research is needed to determine the prevalence of these diagnostic categories.
Finally, this review reports the prevalence of eating disorders according DSM-5 criteria. In a historical perspective there have been important changes to the diagnostic criteria since AN and BN were introduced in the DSM-III [32] in 1980. For example, in the DSM-III, the weight loss criteria for AN was “25% below original body weight”, which was then revised to “body weight less than 85% of that expected” in the DSM-IV [1], and subsequently, redefined in the DSM-5 [2] to “significantly low body weight”. For BN there were no criteria for frequency of binge eating and compensatory behavior in the DSM-III. With the DSM-III-R update, the frequency was specified to twice a week, and in DSM-5, it was reduced to once a week. These revisions will greatly influence prevalence rates in the years to come, and are crucial to address when comparing DSM-5 based prevalence to earlier epidemiological studies in EDs.
Strengths and limitations
This is the first systematic review of DSM-5 prevalence studies in EDs, and offers the reader an early snapshot of the extant prevalence literature. The core strength of the study is the thoroughness of the systematic literature review, and the detailed screening process conducted by two of the authors. Conversely, only one database was used to search the literature and only articles that were written in English (or had an available published English translation) were reviewed representing a limitation of the current study. Further, a meta-analysis was not performed which also represents a potential weakness. In addition, our search date (February 2017) dates our paper. In this interim, three publications relevant to the scope of our paper have been published. Hay et al. [33] investigated the prevalence and burden of ARFID and other DSM-5 EDs in an Australian population, Ernst et al. [34] explored how the DSM-5 revisions affected the prevalence, sex ratio and diagnostic distribution of EDNOS/OSFED in a student sample, and Micali et al. [35] investigated lifetime and 12-month prevalence of EDs amongst women in mid-life. Their relevance to the extant literature warrant a more detailed account in future epidemiological ED studies.