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 RESEARCH ARTICLE

Skin picking disorder is associated with other body-focused repetitive behaviors: Findings from an Internet study

Ivar Snorrason, MA

Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, WI, USA

Emily J. Ricketts, MS

Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, WI, USA

Christopher A. Flessner, PhD

Department of Psychology, Kent State University, Kent, OH, USA

Martin E. Franklin, PhD

Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, PA, USA

Dan J. Stein, MD, PhD

Department of Psychiatry and Mental Health, University of Cape Town, Cape Town, South Africa

Douglas W. Woods, PhD

Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, WI, USA

BACKGROUND: There is a lack of consensus on how to conceptualize skin picking disorder (SPD). It has been proposed that SPD is related to other problematic body-focused repetitive behaviors (BFRBs), such as hair pulling disorder (HPD) and problematic nail biting and cheek biting.

METHODS: We compared rates of BFRBs in online samples of SPD sufferers and college students. We also examined family history of HPD and skin picking problems and correlates of BFRB comorbidity in the SPD sample.

RESULTS: Prevalence of BFRBs was significantly higher in the SPD sample compared with the college student sample. One-half (50.8%) of the SPD sample had a first-degree relative with problematic skin picking, and 7.9% had a first-degree relative with diagnosed HPD. Finally, correlates of BFRB comorbidity indicated that when multiple habits co-occur in an individual, they tend to involve the same body area.

CONCLUSIONS: These findings are the first to show that SPD and BFRBs other than HPD frequently co-occur. Furthermore, they extend previous work showing that SPD has a family component and suggest that SPD and HPD may run in the same families. Given the recruitment method and the self-report nature of the comorbidity data, replication in clinical samples is needed.

KEYWORDS: skin picking, body-focused repetitive behavior, comorbidity, family history, hair pulling, trichotillomania

ANNALS OF CLINICAL PSYCHIATRY 2012;24(4):292-299

  INTRODUCTION

Skin picking disorder (SPD; also known as pathological skin picking or psychogenic/neurotic excoriation) is a chronic condition characterized by recurrent picking of the skin that results in lesions, emotional distress, or functional impairment, and is not exclusively due to a dermatologic problem.1 SPD frequently is associated with significant morbidity and impairment,2,3 and studies suggest a prevalence of 1.4% in the general population4 and 2.2% among college students.5

SPD has received limited empirical attention, and there is no consensus on how to conceptualize or categorize this disorder.1,6 Historically, SPD has been classified as an impulse-control disorder not otherwise specified, a stereotypic movement disorder,7 an obsessive-compulsive spectrum disorder,8 a behavioral addiction,9 and a form of self-injurious behavior.10 Limited empirical data exist to support unequivocally any of these approaches.

A conceptualization that has received increasing attention and empirical support is the notion that skin picking is one of several body-focused repetitive behaviors (BFRBs).1,11-13 This approach assumes relatedness between various problematic habit behaviors that are directed toward the body, including SPD, hair pulling disorder (HPD; trichotillomania), and pathological nail biting and cheek/lip biting. These problems respond to the same behavioral treatment (habit reversal)14-17 and, perhaps more importantly, share a number of key phenomenological features. For example, studies show that these behaviors tend to occur automatically (ie, without reflective awareness) but also can function to regulate affect/arousal.11,18-23 Furthermore, a significant portion of sufferers across different BFRBs report associated habits, often involving oral stimulation. For example, individuals with HPD and SPD often play with the product (the hair or the skin) after it is pulled or picked; stroking it against the mouth, chewing on it, or eating it.21,24 Finally, preliminary data suggest familial and genetic associations between some of these problems.25-27

With the exception of HPD, none of the proposed BFRBs are included in DSM-IV. However, a work group recommended that SPD should have its own distinct diagnostic category in DSM-5.1 Both SPD and HPD co-occur and share familiality with obsessive-compulsive disorder (OCD),28 and it has been suggested that these disorders could be classified in the chapter on obsessive-compulsive and related disorders.29 Specific diagnostic criteria for other BFRB disorders (eg, pathological nail biting or cheek/lip biting) have not been proposed; however, it has been recommended that BFRB disorders be mentioned specifically in the category of obsessive-compulsive or related disorders not elsewhere classified.

During the DSM-5 review process, it has been noted that SPD, HPD, and other BFRBs may have a stronger association with each other than with OCD,29 and the possibility of an overall BFRB diagnostic category encompassing these disorders has been discussed.1,29 An argument for the BFRB category would be strengthened if these problems were shown to co-occur frequently and share family history. Although evidence suggests that SPD and HPD often co-occur and may run in the same families,30 existing studies are limited due to small sample sizes. Also, little is known about the co-occurrence of SPD and BFRBs other than HPD.

The aim of the present study was to compare the rates of problematic BFRBs (ie, problematic hair pulling, cheek/lip biting, nail biting, and nose picking) in online samples of college students and individuals with SPD. We predicted that individuals in the SPD sample would report higher rates of problematic BFRBs compared with individuals in the general college student sample. We also investigated family history of both skin picking problems and HPD diagnosis in the SPD sample and predicted that familiality of both would be commonly reported.

Another aim of the study was to explore whether co-occurring habits would tend to involve the same body area. Clinical experience indicates that when patients have multiple BFRBs (eg, hair pulling and skin picking), they serve the same function (eg, arousal regulation), are triggered by the same cues, and often are performed in the same episode. Thus, co-occurring habits may be more likely to develop in areas that preexisting habits focus on. In order to investigate this, we examined whether skin picking-related oral habits (eg, eating or chewing the skin afterwards) were associated with those BFRBs that involve oral behaviors (eg, nail biting and cheek/lip biting). Secondly, we investigated whether picking sites (eg, face, scalp, or fingers/cuticles) would be associated with BFRBs that focus on that body area. We predicted that individuals who pick at their fingers/cuticles would be more likely to report problematic nail biting, those who pick at their scalp would be more likely to report problematic hair pulling, and those who pick at their face would be more likely to report problematic hair pulling or nose picking.

  METHODS

Participants

The SPD sample was recruited through an online survey posted on various websites thought to be visited by people with SPD (ie, support groups, online treatment resources, etc.). The sample and the recruitment method have been described elsewhere.3 A total of 1,663 individuals initially responded to the survey, but a substantial proportion did not continue the survey after consenting or failed to complete relevant items for the current study. Also, a substantial proportion did not meet the following inclusion criteria: 1) age ≥18; 2) current repeated skin picking that results in tissue damage; 3) skin picking that results in at least “mild to moderate” functional impairment in 1 of 5 life domains: home, work, school, relationships, or social life; and 4) skin picking that is not due to psychotic symptoms (eg, delusion of parasitosis), dermatologic illness, or drug use. A total of 718 individuals met these criteria and answered the items relevant to the current study. The sample included 681 (95%) females and 36 (5%) males (1 individual did not report sex). The mean age of the sample was 33.92 years (SD = 11.86; range, 18 to 69).

The student sample consisted of undergraduate psychology students who responded to an online survey in exchange for extra credit. The sample included 211 (77.3%) females and 62 (22.7%) males, with a mean age of 21.7 (SD = 4.5; range, 18 to 52). The college student sample was significantly younger than the SPD sample: t (989) = -16.545; P < .001. The institutional review board of the University of Wisconsin-Milwaukee approved both surveys.

Measures

Skin Picking Impact Project.3 This online survey was completed by the SPD sample and consisted of a variety of questions concerning impact, phenomenology, and clinical characteristics of SPD. The portion of the survey used in the current study included questions about history of problematic BFRBs (see next section) and the presence of the following skin picking–related oral habits (dichotomous, check if present): 1) using the teeth to manipulate the skin (in addition to picking); 2) biting/gnawing the skin (in addition to picking); 3) chewing the skin afterward; and 4) eating the skin afterward. These 4 items had high internal consistency (α = 0.81) and were summed up to produce a total score reflecting the number of skin picking–related oral habits. The survey also included questions about family history of skin picking problems (ie, any first-degree relative with problematic skin picking) and HPD (any first-degree relative who has been diagnosed with HPD) as well as DSM-IV diagnostic questions about HPD (ie, current hair pulling with preceding tension and subsequent relief, resulting in hair loss, distress, or functional impairment).

The college student survey. The college students completed a 20-minute survey unrelated to the current study, which also included questions about problematic BFRBs (see below).

BFRBs. Both the college student survey and the survey administered to the SPD sample included the following questions about problematic BFRBs:

Have you ever engaged in any of the following activities?

A) Recurrent picking/scratching at your nose resulting in damage (eg, frequent nosebleeds, painful scabbing, a hole in the nasal passageway)?

B) Recurrent biting of nails resulting in damage (eg, infection of the nail beds or tissue around nails)?

C) Recurrent biting of lips or cheeks resulting in damage (eg, scarring, oral bleeding)?

D) Have you ever pulled out your hair, resulting in noticeable hair loss, such as bare patches, or thinning of hair?

Response options were No, Yes (in the past 2 weeks), and Yes (at some point in my life). Individuals endorsing either the past 2 weeks or at some point in life were classified as having BFRBs.

Skin Picking Scale-Revised (SPS-R).31 The SPS-R is an 8-item self-report scale designed to assess overall clinical severity of SPD during the past week. The SPS-R has 2 subscales, one assessing symptom severity (frequency and intensity of urges, time spent picking, and controllability) and the other assessing impairment due to SPD (emotional distress, interference, social avoidance, and skin damage due to picking). All items are rated on a 5-point scale, from 0 to 4. Previous study has demonstrated good psychometric properties of this instrument.31

Statistical analysis

We calculated independent sample t tests to examine the difference in rates of each of the BFRBs between the student and the SPD samples. In order to examine correlates of BFRB comorbidity, we conducted a series of logistic regressions with each of the BFRBs as an outcome variable (1 = presence of the disorder; 0 = absence of the disorder). For each regression we entered number of skin picking–related oral habits and picking sites (face, scalp, and fingers) as predictors. Also, because the association between BFRB comorbidity and oral habits simply may be because both are markers of severity, we entered the SPS-R severity and impairment subscales in the models to control for overall clinical severity.

  RESULTS

Prevalence of BFRBs

As shown in TABLE 1, the prevalence of all the BFRBs was numerically higher in the SPD sample, and the difference was statistically significant on all occasions except for a few categories among males, possibly due to small sample sizes. We also examined how many participants in the SPD sample endorsed DSM-IV criteria for current HPD7 and found that 29.7% met those criteria.


TABLE 1

Prevalence of problematic BFRBs in an SPD sample (N = 718) and a college student sample (N = 273/144)

  Group Males, % Females, % Overall, %
Nose picking Controls 25.8% 10.4% 13.9%
SPD 38.9%a 37.8%b 37.8%b
Nail biting Controls 24.2% 30.3% 28.9%
SPD 57.1%c 51.1%b 51.3%b
Cheek biting Controls 17.7% 32.2% 31.9%
SPD 33.3%a 47.5%b 46.7%b
Hair pullingd Controls 2.6% 3.8% 3.5%
SPD 36.1%b 48.1%b 47.5%b
At least 1 BFRB Controls 48.4% 49.3% 49.1%
SPD 75.0%b 84.0%b 83.4%b
aNot significant.
bP < .0001.
cP < .01.
dDue to an error in data collection, only 144 out of the 273 college students answered the question about problematic hair pulling.
BFRBs: body-focused repetitive behaviors; SPD: skin picking disorder.
Family history of problematic skin picking and HPD

Approximately one-half (50.8%) of the SPD sample reported having a first-degree relative with problematic skin picking, and 7.9% had a first-degree relative with a history of an HPD diagnosis.

Correlates of BFRB comorbidity in the SPD sample

Results from the logistic regressions showed that number of skin picking-related oral habits added to the prediction of nose picking, nail biting, and cheek/lip biting, but not to hair pulling (TABLES 2 TO 5). Also, picking sites generally were associated with the site of the comorbid BFRB. Individuals who endorsed picking at their fingers/cuticles were more likely to have comorbid nail biting and cheek/lip biting problems, compared with individuals who did not report picking at the fingers/cuticles. Individuals who picked at their scalp were more likely to have a hair pulling problem than individuals who did not pick at their scalp. Finally, individuals who pick at their face were more likely to endorse a nose picking problem than individuals who did not report picking at the face (TABLES 2 TO 5).


TABLE 2

Summary of results from logistic regression predicting problematic nose picking

Predictors B SE OR Exp(B) 95% CI for
Exp(B)
SPS-R severity 0.035 0.035 1.035a 0.967 to 1.108
SPS-R impairment 0.011 0.038 1.011a 0.939 to 1.090
No. of oral habitsb 0.308 0.065 1.361c 1.197 to 1.546
Picking at fingers –0.167 0.190 0.847a 0.584 to 1.228
Picking at face 0.442 0.204 1.557d 1.044 to 2.321
Picking at scalp 0.283 0.169 1.327a 0.953 to 1.847
Constant –1.637 0.338 0.195c
R2(Cox and Snell) = 0.058 and R2(Nagelkerke) = 0.079.
aNot significant.
bSkin picking related.
cP < .001.
dP < .05.
OR: odds ratio; SE: standard error; SPS-R: Skin Picking Scale-Revised.

TABLE 3

Summary of results from logistic regression predicting problematic nail biting

Predictors B SE OR Exp(B) 95% CI for
Exp(B)
SPS-R severity 0.015 0.036 1.015a 0.946 to 1.089
SPS-R impairment –0.030 0.041 0.971a 0.896 to 1.052
No. of oral habitsb 0.504 0.075 1.655c 1.430 to 1.916
Picking at fingers 1.040 0.193 2.830c 1.940 to 4.128
Picking at face 0.293 0.207 1.341a 0.894 to 2.010
Picking at scalp 0.148 0.175 1.159a 0.822 to 1.635
Constant –0.925 0.345 0.397d
R2(Cox and Snell) = 0.177 and R2(Nagelkerke) = 0.236.
aNot significant.
bSkin picking related.
cP < .001.
dP < .05.
OR: odds ratio; SE: standard error; SPS-R: Skin Picking Scale-Revised.

TABLE 4

Summary of results from logistic regression predicting problematic cheek/lip biting

Predictors B SE OR Exp(B) 95% CI for
Exp(B)
SPS-R severity 0.038 0.034 1.038a 0.971 to 1.110
SPS-R impairment –0.022 0.038 0.978a 0.909 to 1.054
No. of oral habitsb 0.341 0.066 1.406c 1.235 to 1.601
Picking at fingers 0.464 0.182 1.590d 1.113 to 2.272
Picking at face 0.259 0.196 1.295a 0.882 to 1.901
Picking at scalp 0.012 0.166 1.012a 0.731 to 1.401
Constant –0.880 0.324 0.415d
R2(Cox and Snell) = 0.080 and R2(Nagelkerke) = 0.106.
aNot significant.
bSkin picking related.
cP < .001.
dP < .05.
OR: odds ratio; SE: standard error; SPS-R: Skin Picking Scale-Revised.

TABLE 5

Summary of results from logistic regression predicting problematic hair pulling

Predictors B SE OR Exp(B) 95% CI for
Exp(B)
SPS-R severity –0.066 0.034 0.936a 0.876 to 1.000
SPS-R impairment –0.021 0.037 0.979a 0.911 to 1.053
No. of oral habitsb 0.066 0.063 1.068a 0.944 to 1.209
Picking at fingers –0.147 0.182 0.863a 0.604 to 1.234
Picking at face –0.375 0.192 0.687a 0.472 to 1.000
Picking at scalp 0.709 0.164 2.032c 1.473 to 2.805
Constant 0.436 0.319 1.547
R2(Cox and Snell) = 0.052 and R2 (Nagelkerke) = 0.069.
aNot significant.
bSkin picking related.
cP < .001.
OR: odds ratio; SE: standard error; SPS-R: Skin Picking Scale-Revised.

  DISCUSSION

The main aim of the study was to examine the co-occurrence between SPD and various problematic BFRBs. The majority of the SPD sample had a lifetime history of at least 1 other problematic BFRB, and all the BFRBs generally were more common in the SPD sample than in the college student sample.

Of all the BFRBs, HPD has received the most research attention and is the only 1 included in the DSM. Therefore, in addition to asking about problematic hair pulling, we inquired further about HPD diagnosis and found that about one-third (29.7%) of the SPD sample met stringent DSM-IV criteria for current HPD. These findings fall within the range of findings from previous studies using diagnostic interviews to determine the prevalence of HPD in SPD samples (for a review, see reference 30). Prevalence of BFRBs other than hair pulling has not previously been examined in an SPD sample. Nonetheless, our data showing high rates of these behaviors in the SPD sample are consistent with research suggesting genetic and familial links between nail biting, skin picking, and hair pulling.25 These data also are consistent with previous studies showing high rates of BFRBs in HPD samples.12

In addition to investigating the co-occurrence of BFRBs, we examined family history of problematic skin picking and diagnosis of HPD. More than one-half of the SPD sample reported having a first-degree relative with skin picking problems, which is consistent with a recent twin study showing a genetic component underlying this problem.32 Moreover, even though the issue of familiality across different BFRBs needs further study, our data suggested a possible family relation between SPD and HPD. A total of 7.9% of the SPD sample reported a family history of HPD diagnosis, a figure that is much higher than reported in samples of relatives of individuals in the general population (0%).33

Finally, we found some correlates of BFRB comorbidity in the SPD sample. First, individuals who reported skin picking-related oral habits were more likely to have co-occurring BFRBs that involve oral behaviors, including nail biting and cheek/lip biting. Second, the body areas from which the individuals picked predicted other BFRBs in that area. For example, individuals who picked at their fingers or cuticle were almost 3 times more likely to have a nail biting problem, and individuals who picked at their scalp were 2 times more likely to have a hair pulling problem. Taken together, these findings are consistent with the notion that when multiple habits co-occur in an individual, they tend to involve the same body area. However, it should be noted that hair pullers sometimes pull hairs on the face (ie, eyelashes or eyebrows), but a co-occurring hair pulling problem was not associated with picking at the face. These null findings could possibly be explained by lack of power due to low number of eyelash/eyebrow pullers in the sample. Unfortunately, pulling sites were not assessed in the study, so this possibility could not be examined.

The large sample size represents a significant strength of the study; however, using a self-report Internet survey is a limitation, as it precludes verification of SPD diagnoses. Also, the self-report nature of the data and relatively inclusive criteria for the BFRBs (eg, single question without exclusionary criteria) may have led to overestimation of the prevalence of these problems. In order to have an accurate estimate of the co-occurrence between SPD and other BFRBs, further studies using validated instruments and strict diagnostic criteria are needed. Nonetheless, the comparison with the student sample suggests that prevalence of these problems among individuals with SPD is unusually high. It also should be mentioned that mounting evidence suggests that online surveys tend to produce results similar to paper and pencil questionnaires or interviews.34,35 Another potential limitation of the study is the difference in age between the SPD and student samples. However, given that BFRBs typically are chronic and have onset before age 18, this may not be a serious concern, and it seems unlikely that the age difference would produce such differences in the rates of BFRBs. Finally, relying on information from the participants about skin picking and hair pulling problems in a family member can be problematic,36 and further controlled studies in which relatives are interviewed directly are needed to confirm the current findings.

  CONCLUSIONS

Increasing empirical literature suggests that SPD and other BFRBs can be associated with significant morbidity,3,17 but they remain underrecognized and undertreated. Our findings showing high rates of BFRBs in the SPD sample, and potential shared family history of SPD and HPD, provide empirical support for the notion of classifying SPD with HPD in DSM-5, possibly along with other BFRBs.1 Further studies are needed to better understand the extent to which different BFRBs share etiologic mechanisms or reflect the same underlying disorder.

DISCLOSURES: Dr. Franklin receives grant or research support from the National Institute of Mental Health (# RO1 MH079377/RO1 MH077197) and the Tourette Syndrome Association. Dr. Stein has received research grants and/or consultancy honoraria from Abbott, AstraZeneca, Eli Lilly and Company, GlaxoSmithKline, Jazz Pharmaceuticals, Johnson & Johnson, Lundbeck, Orion, Pfizer, Pharmacia, Roche, Servier, Solvay, Sumitomo, Takeda, Tikvah, and Wyeth. Dr. Woods receives grant or research support from the National Institute of Mental Health (#5 RO1 MH080966-02) and the Tourette Syndrome Association, is a speaker for the Tourette Syndrome Association, and receives book royalties from Guilford Press, Oxford University Press, and Springer Press. Drs. Franklin, Flessner, Stein, and Woods serve on the scientific advisory board of the Trichotillomania Learning Center. Mr. Snorrason and Ms. Ricketts report no financial relationship with any company whose products are mentioned in this article or with manufacturers of competing products.

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CORRESPONDENCE: Ivar Snorrason University of Wisconsin-Milwaukee, Department of Psychology, 2441 East Hartford Avenue, Milwaukee, WI 53211 USA E-MAIL: ivarsnorrason@gmail.com