Introduction

Excoriation (Skin Picking) Disorder (SPD), also known as psychogenic, compulsive skin picking, dermatillomania, or neurotic excoriation, was initially described as a long-term condition that has similarities with both Obsessive-Compulsive Disorder (OCD) and Impulse Control Disorder (ICD) (Keuthen, Deckersbach, et al., 2001; Snorrason, Belleau, et al., 2012). Nowadays, SPD has its own diagnostic classification in the International Classification of Diseases, 10th revision (ICD-10) (World Health Organization, 2015) under the code F42.4, in the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition Text Revised (DSM-5-TR) under the category of “Obsessive-Compulsive and Related Disorders” (American Psychiatric Association, 2013) and in the Subjective Experience—S Axis (Trichotillomania and Excoriation Disorder) of the Psychodynamic Diagnostic Manual Version 2 (PDM-2; Lingiardi & McWilliams, 2017). According to nosographical manuals, SPD is a psychiatric disorder in which an individual repeatedly picks at their skin (Calikusu et al., 2012). The most frequently impacted body regions include the face, arms, and hands (Calikusu et al., 2012; Mevorach et al., 2019; Storch & McKay, 2014). In more severe instances, various body locations may also be affected (Odlaug & Grant, 2008; Tucker et al., 2011). The layer of teased skin may consist of healthy skin, small skin anomalies such as pimples or calluses, or scabs produced from prior teasing (Keuthen et al., 2010; Snorrason & Lee, 2022). Individuals with SPD often use fingernails, tweezers, and pins to stimulate their skin (Odlaug & Grant, 2008; Tucker et al., 2011) Compulsive skin picking can persist for extended periods, often lasting for multiple hours each day and potentially continuing for months or even years (Tucker et al., 2011). Skin plucking can happen awarely, automatically, or both (Roos et al., 2015; Snorrason et al., 2010). It additionally can trigger adverse emotions, cognitions and sensations (Flessner & Woods, 2006; Tucker et al., 2011), as well as psychosocial impairment, such as: social avoidance, social embarrassment and loss of productivity in professional settings (Flessner & Woods, 2006; Tucker et al., 2011). Another characteristic of SPD is that individuals’ persistent attempts to diminish or cease the activity without achieving success (Mevorach et al., 2019; Snorrason & Lee, 2022). To receive a formal diagnosis of SPD, this behavior must not be primarily caused by another mental condition or substance usage (Calikusu et al., 2012; Snorrason & Lee, 2022). The lifetime prevalence of SPD in adults is 1.4%, with three-quarters of affected persons being female (Grant & Chamberlain, 2020; Hayes et al., 2009). However, emerging literature suggests that this problematic can get more severe (Gallinat et al., 2019) and its prevalence is higher than previously thought (Hayes et al., 2009; Prochwicz et al., 2016). The onset typically occurs during adolescence and is frequently linked to the presence of acne (Odlaug & Grant, 2008; Snorrason & Lee, 2022). Notably, approximately 1.2% of the general population meet the above-mentioned diagnostic criteria for SPD (Mevorach et al., 2019; Snorrason, Belleau, et al., 2012). The severity of SPD is associated with decreased quality of life as well as increased anxiety disorders (up to 48%), major depression (8–28%), and substance abuse (14–36%) (Grant & Chamberlain, 2017, 2020; Lochner et al., 2017; Mevorach et al., 2019). From a physiological point of view, excoriation disease can be classified as a motor-act, and there is some overlap in its psychobiology with other motor-actions. Indeed, excoriation disorder is a multifaceted psychiatric syndrome that includes symptoms related to emotions, thoughts, thinking, and movement (Torales et al., 2020). In a recent literature review on psychocutaneous disorders from a psychotherapeutic perspective (Zagami et al., 2023), nonpharmacologic treatment modalities encompass a range of therapeutic approaches, including psychotherapy modalities such as cognitive-behavioral therapy (CBT), psychodynamic therapy, and habit reversal therapy. Additionally, transcranial magnetic stimulation (TMS) and additional therapies like psychoeducation, yoga, meditation, mindfulness, aerobic exercise, relaxation techniques, hypnosis, acupuncture, and biofeedback are utilized (Zagami et al., 2023). Minimal research has been conducted on SPD, especially regarding the validated assessment tools available to clinicians for recognize such disorder. This mini review aims at discussing the existing evidence on the most widely used psychometric tools employed in clinical settings for assessing the severity of SPD symptoms.

Assessment and diagnosis of excoriation disorder

SPD is diagnosed when skin picking cannot be predominantly attributed to another medical issue such as scabies or acne (Calikusu et al., 2012; Flessner & Woods, 2006). Nonetheless, an underlying dermatological problem might trigger and worsen SPD (Mevorach et al., 2019; Prochwicz et al., 2016). The degree of independence of the SPD from the underlying dermatological illness determines the distinction between the two clinical scenarios. For this reason, conducting a comprehensive differential diagnosis can lead to a more precise case formulation and the development of a more efficient therapeutic intervention. Diagnostic criteria for SPD diagnosis are synthetized in Table 1. The assessment must concentrate on the injuries, discomfort caused, and teasing-related disorders that can impact self-esteem and lead to social difficulties (Jafferany & Patel, 2019; Snorrason, Belleau, et al., 2012). In particular, SPD can be diagnosed using clinical interviews or standardized assessment tools capable of evaluating the severity and types of teasing behavior. These materials can also aid clinicians during screening and treatment monitoring (Jafferany & Patel, 2019). A summary of the instruments currently used for assessing the severity of SPD symptoms is displayed in Table 2.

Table 1 Diagnostic criteria of excoriation (skin picking) disorder (SPD; APA, 2013)
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Table 2 Tools identified in literature for SPD assessment
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Tools description

The Skin Picking Scale (SPS; Keuthen et al., 2001) is a self-report questionnaire including 6 items designed to assess symptoms of SPD. It evaluates the frequency and severity of urgency, time spent on skin picking, interference caused by skin picking, distress related to skin picking, and avoidance. It can serve as a screening tool. The scores can vary between 0 and 24. A score of 7 or higher indicates a high likelihood of a skin picking disorder (Bewley et al., 2014). The Skin Picking Scale-Revised (SPS-R; Snorrason, Ólafsson, et al., 2012) is an updated version of the original SPS. The SPS-R includes two additional items compared to the previous version, resulting in an 8-question self-report questionnaire (Snorrason et al., 2013; Snorrason, Ólafsson, et al., 2012). The Skin Picking Impact Scale (SPIS; Snorrason et al., 2013) is a self-report questionnaire with 10 items designed to evaluate the psychosocial effects of excoriation disorder during the past week. The questions pertain to self-criticism or skin damage. The scale utilized is a 6-point Likert scale ranging from 0 (none) to 5 (severe), with a maximum score of 50. In validation studies, the clinical threshold value of 7 was determined to indicate the existence of SPD (Keuthen, Deckersbach, et al., 2001; Snorrason et al., 2013). The Skin Picking Symptom Assessment Scale (SP-SAS; Grant et al., 2007) is a self-assessment tool that evaluates impulsivity, thoughts, and behaviors associated with skin picking over the past week. The assessment comprises 12 items rated on a Likert scale ranging from 0 to 4, with a total possible score of 48. Increased scores indicate more severe skin picking symptoms. Overall, the SP-SAS has shown strong reliability and validity (Grant et al., 2007). Among other self-report instruments, the Skin Picking Reward Scale consists of 12 questions on a 5-point Likert scale; the purpose of this self-report instrument is to assess the degree of satisfaction in enacting skin-picking behaviors, in which reward mechanisms are believed to play a pivotal role (Snorrason et al., 2015). Another diagnostic instrument that can be used to assess SPD is the Milwaukee Inventory for the Dimensions of Adult Skin Picking (MIDAS), a self-report questionnaire with 12 items that can be answered using a Likert scale (“not true for any of my picking,” “true for about half of my picking,” and “true for all of my picking”; Walther et al., 2009). Moreover, another available instrument for the assessment of SPD is the Skin Picking Disorder– Dimensional Scale (LeBeau et al., 2013), which measures the severity of skin-picking symptomatology during the previous week through a 5-item self-report questionnaire. Specifically the instrument assess: (1) frequency of picking, (2) distress associated to this condition, (3) control, (4) avoidance, and (5) interference with everyday life (LeBeau et al., 2013; Russell et al., 2020). In addition to the self-report measures afore mentioned, also three clinician-rated measures were found in the literature to formulate a diagnosis for SPD: the Yale-Brown Obsessive Compulsive Scale Modified For Neurotic Excoriation (NE-YBOCS; Arnold et al., 1999; Aydin et al., 2021), the Keuthen Diagnostic Inventory for Skin Picking (K-DISP) for DSM-5 (Hallion et al., 2017), the Diagnostic Interview for Skin Picking Problems (DISP; Snorrason, Belleau, et al., 2012; Snorrason & Lee, 2022). The latter consists of a semi-structured interview (16 questions) to assess clinical features for a formal diagnosis of SPD. Items are organized into four domains: (1) SPD diagnosis according to DSM-5 criteria, (2) symptom presentation, (3) phenomenology, and (4) course of the disorder. Items were developed based on literature findings and authors’ clinical experience. The NE-YBOCS; (Arnold et al., 1999; Aydin et al., 2021) is a semi-structured, clinician administered scale that evaluates the severity of the disorder over the previous week using 10 items. Each item is scored 0–4, yielding a total score of 0–40. The first 5 items assess the time spent on urges and thoughts of skin picking, analyzing the effect of these thoughts on daily functioning, the consequent distress caused by these thoughts, and the desire to control these thoughts.The second half of the scale focuses on picking behavior: time spent picking, interference and distress due to the behavior and ability to control the behavior. Although no validity and reliability studies of the NE-YBOCS have been conducted, this instrument is often used to evaluate treatment outcomes in clinical trials, and it has shown good psychometric properties (Aydin et al., 2021; Bloch et al., 2001; Grant et al., 2007, 2010).

Results and discussion of the current evidence

Searching the database PubMed, using keywords such as “Excoriation Disorder”, “Skin Picking Disorder”, and “Dermatillomania”, linked with the operator OR, we noticed that a variety of tools are used in clinical settings to assess SPD symptoms. These include both self-report measures, such as SPS-R, SP-SAS, SPIS, SPRS and MIDAS, as well as clinician-rated measures, notably, K-DIPS and DISP. The articles included in this review had to meet the following inclusion criteria: (1) Publication year equal to or subsequent 2013, since this disorder was considered as a specific diagnosis only since the publication of the Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5; American Psychiatric Association, 2013); (2) publication in English; (3) assessment of a human sample; (4) longitudinal or cross-sectional study design; (5) inclusion of only participants with a clinical diagnosis of SPD according to the DSM-5, DSM-5-TR or ICD-10; and (6) utilization of a standardized measure for the assessment of SPD symptomatology.

See Table 3 for a summary of the characteristics of the studies we have considered for the present mini review. Investigations that have dealt with the assessment of SPD are equally divided in cross-sectional studies (Blum et al., 2018; Dieringer et al., 2019; Grant, Chamberlain, et al., 2016; Grant et al.,2017, 2021; Grant & Chamberlain, 2017, 2022; Harries et al., 2017; Schienle, 2018; Valle et al., 2022; Xavier et al., 2019, 2022), and longitudinal studies (Asplund et al., 2021, 2022; Aydin et al., 2020; Grant et al., 2022; Grant, Leppink, et al., 2016; Gulassa et al., 2019; Jafferany & Osuagwu, 2017; Mathew et al., 2021; Xavier et al., 2020). Looking at such literature, the scores obtained from clinical research studies do not appear to differ from the mean scores for SPD symptoms severity found in scales validation studies (Asplund et al., 2021, 2022; Aydin et al., 2020; Blum et al., 2018; Dieringer et al., 2019; Grant, Chamberlain, et al., 2016; Grant et al., 2017, 2021, 2022; Grant, Leppink, et al., 2016; Grant & Chamberlain, 2017, 2022; Gulassa et al., 2019; Harries et al., 2017; Jafferany & Osuagwu, 2017; Mathew et al., 2021; Schienle, 2018; Valle et al., 2022; Xavier et al., 2019, 2020, 2022). These findings support the credibility and dependability of these measures, reinforcing their use in clinical practice for both diagnosis and symptom tracking. The varied nature of available tools for assessing SPD suggests diverse implications for clinical practice. Specifically, self-report measures, such as the SPRS, MIDAS, SPS, SPS-R and SP-SAS, might provide clinicians with valuable insights into their patients’ subjective experiences, symptom severity, and psychosocial impact of SPD symptomatology. For instance, the SPRS evaluates the degree of satisfaction associated with the behavior, while the SPS and its revised version assess various dimensions related to skin-picking, including frequency, intensity, and distress. Such tools might be particularly useful in clinical practice for assessing the severity and impact of the disorder, as well as for monitoring therapeutic progress. On the other hand, clinician-rated measures like the K-DISP and DISP offer structured assessments aligned with diagnostic criteria, making them most suitable at the beginning of the diagnostic process for identifying relevant clinical features for SPD diagnosis. Except for the SPS-R (Snorrason & Lee, 2022), average scores in non-clinical populations are typically not given, which limits the screening effectiveness of these tools. It is thus crucial for psychiatric and non-psychiatric physicians, like dermatologists and general medical practitioners, to have access to evaluation tools that can aid in clinical practice and the diagnostic process. The only validated clinician-rated available tool for SPD diagnosis according to DSM-5 criteria is the DISP, which has been recently validated on preliminary data and results support its psychometric accuracy and clinical utility (Snorrason et al., 2022). Validated techniques for detecting SPD symptoms have advantages but also limits. Most of the available instruments for SPD are self-report, which implies that results can be influenced by the patient’s awareness of their disorder. In fact, picking behaviors often occur spontaneously, and individuals may not be completely conscious of them before engaging in them. Interindividual variability in symptom manifestation can also represent a potential factor hindering, the accuracy of SPD assessment, as it is related to diverse experiences and symptom expression. Moreover, the presence of psychiatric or physical comorbidities can further complicate the assessment process, as these conditions may intersect with or exacerbate symptoms of SPD. Additionally, the conciseness of these measures may suggest that they might not fully evaluate certain features of the disease, such as the frequency and duration of the picking activity, the afflicted skin locations, the level of discomfort, and the severity of damage. Most research on SPD assessment tools are conducted in the USA (Blum et al., 2018; Grant, Chamberlain, et al., 2016; Grant et al., 2017, 2021, 2022; Grant, Leppink, et al., 2016; Grant & Chamberlain, 2017, 2022; Harries et al., 2017; Jafferany & Osuagwu, 2017; Mathew et al., 2021), limiting the ability to make cross-country comparisons regarding the usage of SPD evaluation techniques. However, evaluation techniques such as SPS-R, SP-SAS, and SPIS are reliable and effective for diagnosing and monitoring symptoms in SPD clinical groups. Although commonly utilized in clinical research environments, this does not guarantee that clinicians incorporate these techniques into their ordinary practice with patients diagnosed with SPD. Furthermore, while these tools have been translated into other languages, only a few of the translations now in use have been statistically confirmed (Barrios et al., 2021; Gallinat et al., 2017; Kenar et al., 2020; Kłosowska et al., 2022). This research gap can hinder the utilization of these techniques in clinical settings. Given these factors, it is crucial to validate these tools to support their application in clinical environments, for both aiding in diagnosis and monitoring symptoms of SPD. In addition, the identified assessment tools could be appropriately modified and validated for the assessment of other body-focused repetitive behavior disorders, in order to support clinicians for diagnostic and treatment monitoring purposes. This mini review offers significant insights into the existing landscape of SPD evaluation methods, but there is still plenty of room for future research to broaden the scope and depth of the analysis. This may require a thorough analysis of current measures, a clarification of their constraints, and the suggestion of improvements or the creation of new tools to achieve a more thorough and precise evaluation of SPD symptoms.

Table 3 Studies using validated tools for SPD symptoms assessment in clinical samples
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Conclusions

Screening tools for SPD symptoms are accessible in literature and can be utilized in clinical and research environments. SPS-R, SP-SAS, and SPIS represent the most used assessment tools in clinical samples with SPD, but their self-report nature poses some bias problems. So far, the DIPS is the only clinician-rated instrument available for SPD diagnosis based on DSM-5 criteria. However, the predominance of research in the USA underscores the need for broader cross-country comparisons for the utilization of such tools. Despite these limitations, SPD assessment tools have demonstrated reliability and effectiveness in clinical environments. However, their integration into routine practice requires further validation and dissemination. Recent advancements, such as the validation of DISP, offer promise in addressing these gaps, emphasizing the importance of ongoing research to refine and expand the toolkit for diagnosing and monitoring SPD. Moving forward, a comprehensive analysis of existing measures, coupled with efforts to address their limitations and develop new tools, is essential to enhance the precision and utility of SPD assessment in clinical settings. This mini-review provides valuable insights into the current landscape of SPD evaluation methods, highlighting avenues for future research to promote the use of these SDP symptom screening methods in clinical settings and better serve individuals affected by this disorder.