Abstract

Introduction

Skin picking disorder (SPD), also known as excoriation disorder, affects 1.4 to 5.4% of the general population and 7 to 30% of psychiatric patients.¹1. Tucker BT, Woods DW, Flessner CA, Franklin SA, Franklin ME. The skin picking impact project: phenomenology, interference, and treatment utilization of pathological skin picking in a population-based sample. J Anxiety Disord. 2011;25:88-95.,²2. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Arlington: American Psychiatric Publishing; 2013. Its course tends to be chronic, causing negative socioeconomic impact.³3. Machado MO, Köhler CA, Stubbs B, Nunes-Neto PR, Koyanagi A, Quevedo J, et al. Skin picking disorder: prevalence, correlates, and associations with quality of life in a large sample. CNS Spectr. 2018;23:311-20. Among individuals with SPD, 23% have comorbid anxiety disorder and 48% have comorbid depression, sometimes with suicidal ideation.¹1. Tucker BT, Woods DW, Flessner CA, Franklin SA, Franklin ME. The skin picking impact project: phenomenology, interference, and treatment utilization of pathological skin picking in a population-based sample. J Anxiety Disord. 2011;25:88-95.,⁴4. Grant JE, Odlaug bL, Chamberlain SR, Keuthen NJ, Lochner C, Stein DJ. Skin picking disorder. Am J Psychiatry. 2012;169:1143-9.

Despite the importance of this pathology, less than a half of patients with SPD seek treatment, only 53% receive a correct diagnosis, and 57% do not improve after treatment. Moreover, the majority of patients (85%) believe that professionals are not trained to treat SPD.¹1. Tucker BT, Woods DW, Flessner CA, Franklin SA, Franklin ME. The skin picking impact project: phenomenology, interference, and treatment utilization of pathological skin picking in a population-based sample. J Anxiety Disord. 2011;25:88-95. Regarding treatment options, neither antidepressants nor lamotrigine are more effective than placebo, and only behavioral techniques were superior to placebo in clinical trials.⁵5. Schumer MC, Bartley CA, Bloch MH. Systematic review of pharmacological and behavioral treatments for skin picking disorder. J Clin Psychopharmacol. 2016;36:147-52.

6. Selles RR, McGuire JF, Small BJ, Storch EA. A systematic review and meta-analysis of psychiatric treatments for excoriation (skin-picking) disorder. Gen Hosp Psychiatry. 2016;41:29-37.-⁷7. Gelinas BL, Gagnon MM. Pharmacological and psychological treatments of pathological skin-picking: a preliminary meta-analysis. J Obsessive Compuls Relat Disord. 2013;2:167-75. Four studies have evaluated behavioral techniques in SPD treatment, applying 3 to 4 sessions of therapy based on Azrin and Nunn’s habit reversal method, including: self-monitoring, competing response practice, and searching for better social support through family and friends about how to cope with the problem.⁸8. Azrin NH, Nunn RG. Habit-reversal: a method of eliminating nervous habits and tics. Behav Res Ther. 1973;11:619-28. There was improvement in all of these studies after the intervention,⁶6. Selles RR, McGuire JF, Small BJ, Storch EA. A systematic review and meta-analysis of psychiatric treatments for excoriation (skin-picking) disorder. Gen Hosp Psychiatry. 2016;41:29-37.,⁸8. Azrin NH, Nunn RG. Habit-reversal: a method of eliminating nervous habits and tics. Behav Res Ther. 1973;11:619-28. and one study added a session on cognitive techniques.⁹9. Schuck K, Keijsers GP, Rinck M. The effects of brief cognitive-behaviour therapy for pathological skin picking: a randomized comparison to wait-list control. Behav Res Ther. 2011;49:11-7. However, they involved different protocols and had small samples, which makes it difficult to generalize the results.⁶6. Selles RR, McGuire JF, Small BJ, Storch EA. A systematic review and meta-analysis of psychiatric treatments for excoriation (skin-picking) disorder. Gen Hosp Psychiatry. 2016;41:29-37. In addition, their protocols did not address anxious and depressive symptoms associated with SPD.⁶6. Selles RR, McGuire JF, Small BJ, Storch EA. A systematic review and meta-analysis of psychiatric treatments for excoriation (skin-picking) disorder. Gen Hosp Psychiatry. 2016;41:29-37.,¹⁰10. Teng EJ, Woods DW, Twohig MP. Habit reversal as a treatment for chronic skin picking: a pilot investigation. Behav Modif. 2006;30:411-22. One study (n=12) evaluated a cognitive psychophysiological model for body-focused repetitive behaviors (including SPD) that treated the habit-triggering emotional construct rather than the habit itself, finding improvement in depressive and anxious symptoms after the intervention.¹¹11. O’Connor K, Lavoie M, Desaulniers B, Audet JS. Cognitive psychophysiological treatment of bodily-focused repetitive behaviors in adults: an open trial. J Clin Psychol. 2017;74:273-85.

One important limitation of behavioral techniques is the low availability of trained therapists.¹²12. Keuthen NJ, Tung ES, Reese HE, Raikes J, Lee L, Mansueto CS. Getting the word out: cognitive-behavioral therapy for trichotillomania (hair-pulling disorder) and excoriation (skin-picking) disorder. Ann Clin Psychiatry. 2015;27:10-5. Recent studies have found that unified cognitive behavioral therapy (CBT) protocols can effectively treat different pathologies in the same spectrum, facilitating therapist training and improving treatment dissemination.¹²12. Keuthen NJ, Tung ES, Reese HE, Raikes J, Lee L, Mansueto CS. Getting the word out: cognitive-behavioral therapy for trichotillomania (hair-pulling disorder) and excoriation (skin-picking) disorder. Ann Clin Psychiatry. 2015;27:10-5.

13. Farchione TJ, Fairholme CP, Ellard KK, Boisseau CL, Thompson-Hollands J, Carl JR, et al. Unified protocol for transdiagnostic treatment of emotional disorders: a randomized controlled trial. Behav Ther. 2012;43:666-78.-¹⁴14. Gallagher MW, Sauer-Zavala SE, Boswell JF, Carl JR, Bullis J, Farchione TJ, et al. The impact of the unified protocol for emotional disorders on quality of life. Int J Cogn Ther. 2013;6(1). Moreover, group CBT interventions have also been found effective and can treat more patients at the same time.¹⁵15. Health Quality Ontario. Psychotherapy for major depressive disorder and generalized anxiety disorder: a health technology assessment. Ont Health Technol Assess Ser. 2017;17:1-167. Thus, besides treating more patients, effective group CBT interventions could also train therapists in loco, improving cost effectiveness. To our knowledge, no SPD interventions have been tested in a group format.⁶6. Selles RR, McGuire JF, Small BJ, Storch EA. A systematic review and meta-analysis of psychiatric treatments for excoriation (skin-picking) disorder. Gen Hosp Psychiatry. 2016;41:29-37.,¹⁰10. Teng EJ, Woods DW, Twohig MP. Habit reversal as a treatment for chronic skin picking: a pilot investigation. Behav Modif. 2006;30:411-22.

The Rothbaum CBT protocol effectively treats trichotillomania with habit reversal techniques and also manages anxiety and depressive symptoms.¹⁶16. Flessner CA. Cognitive behavior therapy for childhood repetitive behavior disorders: tic disorders and trichotillomania. Child Adolesc Psychiatr Clin N Am. 2011;20:319-28.,¹⁷17. Rothbaum BO. The behavioral treatment of trichotillomania. Behav Cogn Psychother. 1992;20:85-90. Recent studies have found that the rate of co-occurrence of SPD and trichotillomania is higher than expected, and it has been hypothesized that these disorders are part of a single spectrum of pathology.¹1. Tucker BT, Woods DW, Flessner CA, Franklin SA, Franklin ME. The skin picking impact project: phenomenology, interference, and treatment utilization of pathological skin picking in a population-based sample. J Anxiety Disord. 2011;25:88-95.,¹⁸18. Van Ameringen M, Patterson B, Simpson W. DSM-5 obsessive-compulsive and related disorders: clinical implications of new criterea. Depress Anxiety. 2014;31:487-93.,¹⁹19. Snorrason I, Belleau EL, Woods DW. How related are hair pulling disorder (trichotillomania) and skin picking disorder? A review of evidence for comorbidity, similarities and shared etiology. Clin Psychol Rev. 2012;32:618-29.

The aim of the present study was to adapt the Rothbaum CBT protocol to SPD treatment (Study 1) and test its efficacy in individual and group formats (Study 2). This study’s hypothesis was that the Rothbaum protocol would effectively treat SPD, improving skin-picking symptoms, as well as comorbid anxious and depressive symptoms, in both individual and group formats.

Study 1

Methods

Study design and participants

This study was conducted as an open pilot trial with 16 patients allocated to treatment with the adapted Rothbaum protocol in individual or group format, according to the patient’s availability. The sample consisted of individuals who sought treatment at a public hospital’s Psychiatry Service between July 2014 and July 2015 after a public advertising campaign. Inclusion criteria were a diagnosis of SPD according to the DSM-5²2. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Arlington: American Psychiatric Publishing; 2013. and motivation to engage in CBT. Exclusion criteria were a psychotic disorder, intellectual disability or suicide risk according to the Mini International Neuropsychiatric Interview.²⁰20. Sheehan DV, Lecrubier Y, Sheehan KH, Amorim P, Janavs J, Weiller E, et al. The Mini-International Neuropsychiatric Interview (M.I.N.I.): the development and validation of a structured diagnostic psychiatric interview for DSM-IV and ICD-10. J Clin Psychiatry. 1998;59Suppl 20:22-33; quiz 34-57. The sample’s demographic characteristics are presented in Table 1.

Procedure and measures

Under the supervision of a senior researcher, a diagnostic interview was conducted by a psychiatry resident that consisted of the MINI²⁰20. Sheehan DV, Lecrubier Y, Sheehan KH, Amorim P, Janavs J, Weiller E, et al. The Mini-International Neuropsychiatric Interview (M.I.N.I.): the development and validation of a structured diagnostic psychiatric interview for DSM-IV and ICD-10. J Clin Psychiatry. 1998;59Suppl 20:22-33; quiz 34-57. (Brazilian Portuguese version)²¹21. Amorim P. Mini International Neuropsychiatric Interview (MINI): validação de entrevista breve para diagnóstico de transtornos mentais. Braz J Psychiatry. 2000;22:106-15. and a checklist of SPD symptoms according to DSM-5.²2. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Arlington: American Psychiatric Publishing; 2013. Patients who met the inclusion criteria completed a baseline evaluation conducted by two trained evaluators that consisted of the Beck Depression Inventory (BDI),²²22. Gorenstein C, Andrade L. Validation of a Portugues version of the beck depression inventory and the state-trait anxiety inventory in Brazilian subjects. Braz J Med Biol Res. 1996;29:453-7. the Hamilton Anxiety Scale (HAM-A),²³23. Kummer A, Cardoso F, Teixeira AL. Generalized anxiety disorder and the Hamilton anxiety rating scale in parkinson's disease. Arq Neuropsiquiatr. 2010;68:495-501. the Clinical Global Impression (CGI) scale,²⁴24. de Lima MS, Soares BG, Paoliello G, Vieira RM, Martins CM, da Mota Neto JI, et al. The Portuguese version of the clinical global impression – schizophrenia scale: validation study. Braz J Psychiatry. 2007;29:246-9. the Skin Picking Impact Scale (SPIS),²⁵25. Keuthen NJ, Deckersbach T, Wilhelm S, Engelhard I, Forker A, O´Sullivan RL, et al. The Skin Picking Impact Scale (SPIS): scale development and psychometric analyses. Psychosomatics. 2001;42:397-403. and the University of Rhode Island Change Assessment (URICA) instrument.²⁶26. Hasler G, Klaghofer R, Buddeberg C. [The University of Rhode Island Change Assessment Scale (URICA)]. Psychother Psychosom Med Psychol. 2003;53:406-11.

The BDI is a self-report questionnaire that evaluates depressive symptoms; in the validated Brazilian Portuguese version, scores range from 0 to 63, with higher scores indicating more severe symptoms.²²22. Gorenstein C, Andrade L. Validation of a Portugues version of the beck depression inventory and the state-trait anxiety inventory in Brazilian subjects. Braz J Med Biol Res. 1996;29:453-7.,²⁷27. Beck AT, Ward CH, Mendelson M, Mock J, Erbaugh J. An inventory for measuring depression. Arch Gen Psychiatry. 1961;4:561-71. The HAM-A is a questionnaire for evaluating anxiety symptoms; in the validated Brazilian Portuguese version, scores range from 0 to 56, with higher scores indicating more severe symptoms.²³23. Kummer A, Cardoso F, Teixeira AL. Generalized anxiety disorder and the Hamilton anxiety rating scale in parkinson's disease. Arq Neuropsiquiatr. 2010;68:495-501.,²⁸28. Hamilton M. The assessment of anxiety states by rating. Br J Med Psychol. 1959;32:50-5. The CGI scale is a questionnaire for assessing the impact that a disease/disorder has on a patient’s life; in the Brazilian Portuguese version, scores range from 1 (asymptomatic) to 7 (very severe impact).²⁴24. de Lima MS, Soares BG, Paoliello G, Vieira RM, Martins CM, da Mota Neto JI, et al. The Portuguese version of the clinical global impression – schizophrenia scale: validation study. Braz J Psychiatry. 2007;29:246-9.,²⁹29. Busner J, Targum SD. The clinical global impression scale – applying a research tool in clinical practice. Psychiatry (Edgmont). 2007;4:28-37. The SPIS is a self-applied questionnaire³⁰30. Xavier AC, de Souza CM, Flores LH, Prati C, Cassal C, Dreher CB. Improving skin picking diagnosis: validation of the skin picking impact scale and development of a photographic instrument. An Bras Dermatol. 2019;94:553-60. for assessing the severity and life impact of skin picking; the validated Brazilian Portuguese version consists of 10 items on skin-picking habits and their influence on the patient’s daily life during the last week. Each item is rated from 0 to 5 on a Likert scale, and total scores range between 0 and 50, with higher scores indicating more severe impact.²⁵25. Keuthen NJ, Deckersbach T, Wilhelm S, Engelhard I, Forker A, O´Sullivan RL, et al. The Skin Picking Impact Scale (SPIS): scale development and psychometric analyses. Psychosomatics. 2001;42:397-403. The URICA is a self-applied scale that assesses the respondent’s current motivation to change a specific condition. In the validated Brazilian Portuguese version, its 32 randomly ordered questions cover pre-contemplative, contemplative, action or maintenance stages, with higher scores indicating more advanced motivational status.²⁶26. Hasler G, Klaghofer R, Buddeberg C. [The University of Rhode Island Change Assessment Scale (URICA)]. Psychother Psychosom Med Psychol. 2003;53:406-11.,³¹31. Szupszynski KP, Oliveira MS. Brasilian version of the University of Rhode Island Change Assessment (URICA) for illicit substance users. Psico-USF. 2008;13:31-9. The 9-week Rothbaum CBT protocol¹⁷17. Rothbaum BO. The behavioral treatment of trichotillomania. Behav Cogn Psychother. 1992;20:85-90. was adapted into an 8-week format for SPD patients. Sessions 3 and 4 were condensed into a single session due to the content’s similarity and to enhance treatment compliance through a shorter protocol. The adapted Rothbaum protocol maintained the same techniques while changing the target habit from trichotillomania to skin picking. The adapted protocol was applied in weekly sessions of 45 and 90 minutes in individual and group formats, respectively. After the intervention, the baseline questionnaires were reapplied. Under the supervision of a senior CBT therapist, both treatment modalities were conducted by four professionals with theoretical and practical training in CBT (Table 2).

The study’s primary endpoint was the adaptability of the Rothbaum protocol, assessed through dropout rates. Secondary outcomes included improvement in CGI, SPIS, BDI and HAM-A results.

Statistical analysis

Statistical analyses were performed in SPSS version 20.0. Subjects who attended less than 50% of the treatment sessions were included in the statistical analysis through the last observation carried forward model. Variable distribution was analyzed with the Shapiro-Wilk test and a parametric or non-parametric test, according to distribution. The chi-square test was used to compare categorical variables. The significance level was set at p < 0.05.

Ethics statement

All participants gave written informed consent to participate in the research. This study was conducted in accordance with Brazilian National Health Council guidelines and norms regulating research involving human beings and followed the ethical principles of the Declaration of Helsinki. It was approved by the local ethics and research commission (protocol 1,197,672).

Results

The study flow chart is depicted in Figure 1. There was no significant difference in dropout rates between individual and group treatment (0 vs. 28.5%, p = 0.47); both rates are in accordance with the literature.³³33. Carpenter JK, Andrews LA, Witcraft SM, Powers MB, Smits JA, Hofmann SG. Cognitive behavioral therapy for anxiety and related disorders: a meta-analysis of randomized placebo-controlled trials. Depress Anxiety. 2018;35:502-14. Patients who completed the treatment were more motivated according to URICA scores and had less incidence of generalized anxiety disorder (Table 1). The protocol was feasible in both the group and individual modalities, leading to clinical improvement, although no significant change was found in the assessment scales.

Figure 1
Flow diagram of Study 1. CBT = cognitive behavioral therapy.

Study 2

Methods

Study design and participants

This evaluator-blinded clinical trial included 54 patients, who were randomly allocated to treatment with the adapted Rothbaum CBT protocol in an individual (n=27) or group (n=27) format. The sample consisted of individuals who sought treatment at the Psychiatry Service of the Universidade Federal de Ciências da Saúde de Porto Alegre between July 2016 and January 2018 after a public advertising campaign. The inclusion and exclusion criteria were the same as in Study 1. Individuals who were not included in this study were referred to the appropriate community resources. The sample’s demographic characteristics of are presented in Table 3.

Procedure and measures

The baseline evaluation was performed by two blinded evaluators (with high reliability: kappa = 0.9), following the same procedures and applying the same instruments as in Study 1 (URICA, SPIS, BDI, CGI and HAM-A). For Study 2, we also included a photographic instrument developed by two dermatologists to directly evaluate SPD lesions.³⁰30. Xavier AC, de Souza CM, Flores LH, Prati C, Cassal C, Dreher CB. Improving skin picking diagnosis: validation of the skin picking impact scale and development of a photographic instrument. An Bras Dermatol. 2019;94:553-60. All photos were analyzed by two blinded dermatologists with the photographic instrument, which has high internal consistency and moderate reliability. This measure is important since it specifically assesses lesion severity apart from the influence of patient habit awareness or associated depressive/anxious symptoms.³⁰30. Xavier AC, de Souza CM, Flores LH, Prati C, Cassal C, Dreher CB. Improving skin picking diagnosis: validation of the skin picking impact scale and development of a photographic instrument. An Bras Dermatol. 2019;94:553-60.

The patients were randomized in blocks of 6 to receive individual or group treatment. The 8-week Rothbaum CBT protocol adapted for SPD, as described in Study 1, was applied in weekly sessions of 45 minutes for individual treatment and 90 minutes for group treatment, with the same therapists applying both formats.

The study’s primary endpoint was post-intervention symptom remission, characterized by CGI scores ≤ 2.²⁹29. Busner J, Targum SD. The clinical global impression scale – applying a research tool in clinical practice. Psychiatry (Edgmont). 2007;4:28-37. The secondary outcome was change in CGI, SPIS, BDI, HAM-A and photographic instrument results.

Statistical analysis

Statistical analyses were performed in SPSS version 23.0. The sample size was based on a previous study by Schuck et al., which found CBT to be efficacious for SPD in a sample of 34 patients.⁹9. Schuck K, Keijsers GP, Rinck M. The effects of brief cognitive-behaviour therapy for pathological skin picking: a randomized comparison to wait-list control. Behav Res Ther. 2011;49:11-7. Participants who attended less than 50% of the treatment sessions were included in the statistical analysis through the last observation carried forward method. The data were analyzed for normality using the Kolmogorov-Smirnov test, and categorical variables were compared with the Pearson chi-square test, the Yates chi-square test, or Fisher’s exact test. Generalized estimating equations with Bonferroni correction were used to assess improvement in clinical scales after treatment and to compare improvement between treatment modalities. The intervention effect size was calculated with Cohen’s d, using natural logarithm transformation for pre- and post-treatment CGI values.

Ethics statement

The ethical considerations were the same as in Study 1 (approval protocol 1,197,672). This trial was registered in the Clinical Trials database (NCT03182478).

Results

Figure 2 depicts the CONSORT study flow diagram.³⁴34. Schulz KF, Altman DG, Moher D; CONSORT Group. CONSORT 2010 statement: updated guidelines for reporting parallel group randomized trials. Ann Intern Med. 2010;152:726-32. After treatment, 8 patients in individual treatment (29.6%) and 9 in group treatment (33.3%) dropped out before completing at least 50% of the sessions. There was no significant difference in dropout rate between treatment modalities (p = 0.99). There were no differences in patient clinical and sociodemographic characteristics between treatment modalities, except that patients in individual treatment had a higher rate of comorbid social anxiety (Table 3).

Figure 2
Flow diagram for Study 2. CBT= cognitive behavioral therapy; SPD = skin picking disorder.

After treatment with the adapted Rothbaum CBT protocol, both intervention modalities showed high remission rates (individual 63%; group 52%), with no significant difference between intervention types (p = 0.4). The treatment effect size, according to change in global clinical status, was large in both intervention types (Cohen’s d: Group format = 0.88; individual format = 1.15). Global status, skin picking symptoms, comorbid depressive symptoms and skin lesion severity significantly improved after treatment, with no significant differences between intervention types. Anxiety symptoms also improved significantly after treatment in both modalities, although there was more improvement among patients in individual treatment (p = 0.01) (Table 4).

Comparing patients who dropped out before completing at least 50% of the treatment with those who completed treatment, dropouts had a higher prevalence of agoraphobia (37.5% vs. 8.1%, p = 0.009) and were less motivated for treatment according to URICA scores (median 9.8 [6.86-13.71] vs. median 11 [6.4-14] p = 0.02).

Discussion

This study found that adapting the Rothbaum CBT protocol to SPD was feasible and efficacious. We were able to adapt the protocol while maintaining the same structure and techniques – only the target habit changed, which facilitated therapist training. Some new techniques were included specifically for skin picking, such as scab collection and wearing rings, which were well accepted and easily implemented by patients. Dropout rates during treatment were not higher than expected, reflecting the acceptability of the intervention.³³33. Carpenter JK, Andrews LA, Witcraft SM, Powers MB, Smits JA, Hofmann SG. Cognitive behavioral therapy for anxiety and related disorders: a meta-analysis of randomized placebo-controlled trials. Depress Anxiety. 2018;35:502-14.

CBT-based interventions are not always equally effective in group and individual formats.³⁵35. Stangier U, Heidenreich T, Peitz M, Lauterbach W, Clark DM. Cognitive therapy for social phobia: individual versus group treatment. Behav Res Ther. 2003;41:991-1007. Although the group modality has better cost-effectiveness, since it can treat more patients with fewer therapists, patients can sometimes feel inhibited in a group setting, they may not have the patience to wait for a group to be formed, or they may not comply over a several week program due to reduced scheduling flexibility.³⁵35. Stangier U, Heidenreich T, Peitz M, Lauterbach W, Clark DM. Cognitive therapy for social phobia: individual versus group treatment. Behav Res Ther. 2003;41:991-1007. This study found no difference between dropout rates in the two treatment formats, suggesting that the group model can be as efficacious as the individual one. Although the group modality included no patients with social anxiety (and, thus, had no related dropouts), it is possible that some patients refused to participate due to social anxiety. However, since the baseline comorbidity evaluation was performed after inclusion in the study, we cannot confirm this. An important challenge in SPD treatment is the lack of trained therapists and the great demand.¹²12. Keuthen NJ, Tung ES, Reese HE, Raikes J, Lee L, Mansueto CS. Getting the word out: cognitive-behavioral therapy for trichotillomania (hair-pulling disorder) and excoriation (skin-picking) disorder. Ann Clin Psychiatry. 2015;27:10-5. The group format is a viable way to fill this demand and, to our knowledge, this is the first study to evaluate such a format for SPD treatment.

Consistent with previous studies, we found a higher incidence of generalized anxiety disorder and depressive episodes, either past or current, than expected rates for the general population.¹1. Tucker BT, Woods DW, Flessner CA, Franklin SA, Franklin ME. The skin picking impact project: phenomenology, interference, and treatment utilization of pathological skin picking in a population-based sample. J Anxiety Disord. 2011;25:88-95. Although some patients did not fulfill the criteria for anxiety or depressive disorders, many scored high on the BDI and HAM-A scales. These findings show the importance of treating SPD with interventions that include anxiety and depression components, such as the Rothbaum CBT protocol.

Grant et al. found that SPD is frequently associated with anxiety (8-23% of the cases), depression (12.5-48%), substance use (in 14-36% of patients) and major functional impairment.⁴4. Grant JE, Odlaug bL, Chamberlain SR, Keuthen NJ, Lochner C, Stein DJ. Skin picking disorder. Am J Psychiatry. 2012;169:1143-9.,³⁶36. Grant JE, Chamberlain SR. Clinical correlates of symptom severity in skin picking disorder. Compr Psychiatry. 2017;78:25-30. Despite these important findings, there is no current treatment for SPD that includes management of these symptoms. One study with 6 participants evaluated the use of acceptance-enhanced behavior therapy for trichotillomania and chronic SPD, but reported no benefits in managing depression.³⁷37. Keuthen NJ, Rothbaum BO, Falkenstein MJ, Meunier S, Timpano KR, Jenike MA, et al. DBT-enhanced habit reversal treatment for trichotillimania: 3- and 6-month follow-up results. Depress Anxiety. 2011;28:310-3. Another study applied a brief CBT protocol consisting of 4 sessions of psychoeducation, cognition assessment, habit reversal techniques and relapse prevention, but reported no benefits for anxiety or depression (i.e. treatment was no more effective than the waiting list condition).⁹9. Schuck K, Keijsers GP, Rinck M. The effects of brief cognitive-behaviour therapy for pathological skin picking: a randomized comparison to wait-list control. Behav Res Ther. 2011;49:11-7. In this study, both treatment modalities of the adapted Rothbaum CBT protocol resulted in improvement in all assessed symptoms, not only for skin picking but for depression and anxiety as well, which was probably due to the protocol’s cognitive and anxiety coping techniques. Although the group and individual interventions resulted in significant reductions in anxiety, the individual format showed greater improvement, although probably at the cost of improving social anxiety. The effect size for the adapted Rothbaum protocol was considered large in both modalities, larger than CBT interventions for other anxiety disorders.³³33. Carpenter JK, Andrews LA, Witcraft SM, Powers MB, Smits JA, Hofmann SG. Cognitive behavioral therapy for anxiety and related disorders: a meta-analysis of randomized placebo-controlled trials. Depress Anxiety. 2018;35:502-14. Based on these results, as well as the fact that this protocol is short and easy to apply, it can be considered to have good cost-effectiveness.

The photographic instrument results also improved after treatment with the adapted Rothbaum protocol. These results reflect the severity of SPD skin lesions and are a reliable way of determining skin picking habit reduction. Since previous studies have found that change in photographic instrument results is not correlated with change in depression or anxiety symptoms,³⁰30. Xavier AC, de Souza CM, Flores LH, Prati C, Cassal C, Dreher CB. Improving skin picking diagnosis: validation of the skin picking impact scale and development of a photographic instrument. An Bras Dermatol. 2019;94:553-60. it can be hypothesized that the treatment applied in this study directly reduced the skin picking habit, independently of other variables.

It is well known that compliance with CBT is directly associated with better outcomes. In this study we found that the URICA scale was an appropriate way to assess the patients’ readiness to change, thus reflecting motivation for therapy. When a treatment is offered, it is important to consider its cost-effectiveness for patients. Our study shows preliminary data regarding motivation and dropout rates in SPD treatment. If this data is confirmed in other clinical trials, we could hypothesize that patients unmotivated for CBT according to the URICA instrument should not be included in this treatment modality, since the chance of dropout or non-response is high. This is of special concern in group interventions, which can be more cost-effective in public health settings, but cannot replace patients who drop out during therapy.

Our results should be interpreted in light of some limitations. After randomization, the intervention group included no patients with social anxiety, a pathology that is a barrier to group treatment,³⁵35. Stangier U, Heidenreich T, Peitz M, Lauterbach W, Clark DM. Cognitive therapy for social phobia: individual versus group treatment. Behav Res Ther. 2003;41:991-1007. so it is prudent not to generalize our group intervention findings to patients with comorbid social anxiety. Since our study had no follow-up evaluation, generalizations about the long-term efficacy of our results cannot be made. Although the risk of relapse is an important issue in CBT, only one CBT study on SPD has included follow-up (which was only 3 months).⁹9. Schuck K, Keijsers GP, Rinck M. The effects of brief cognitive-behaviour therapy for pathological skin picking: a randomized comparison to wait-list control. Behav Res Ther. 2011;49:11-7. Another study limitation was the lack of a placebo or waitlist control condition. Since the protocol was found efficacious, future studies with control conditions are expected. The main strength of this trial was its two-study format, including adequate design and conservative statistical analysis. This is the first study to have used an SPD treatment that manages important comorbid symptoms in both individual and group formats.

In conclusion, despite being a prevalent disorder, there is currently no treatment for SPD that addresses the management of comorbid symptoms, and no group treatment options exist to overcome low therapist availability. This study found that the Rothbaum CBT protocol for trichotillomania can be adapted to SPD and it effectively led to symptom remission, including improvement in clinical status and in skin picking, anxiety, and depression symptoms, as well as skin lesion severity, both in individual and group formats. These findings are innovative and can fill the current gap in SPD treatment. Follow-up studies evaluating the risk of relapse are expected.

Acknowledgements

The authors would like to thank Dr. Barbara O. Rothbaum, who graciously allowed us to adapt her protocol in our study.

References

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