Skin picking disorder comorbid with ADHD successfully treated with methylphenidate

Skin picking disorder (SPD) is characterized by repetitive picking and scratching of the skin, leading to tissue damage and substantial distress.¹ The few pharmacological studies on SPD treatment have yielded conflicting results² and more pharmacological evidence is needed to guide clinicians.

Attention deficit hyperactivity disorder (ADHD) is characterized by symptoms that express varying levels of inattention, hyperactivity and impulsivity. Case reports of ADHD treatment with psychostimulants suggest they can also act on comorbid disorders with impulsive features (kleptomania, pathological gambling and bulimia nervosa).³ Erdogan et al.⁴ reported that SPD patients had a high prevalence of comorbid ADHD, but this has not been investigated in other studies. The only case report of ADHD comorbid with SPD, by Lane et al.,¹ described a 9-year-old boy with a full-scale IQ of 77 who only experienced improvement when a behavioral intervention was associated with ongoing psychostimulant treatment. There are no case reports describing methylphenidate treatment in ADHD adults comorbid with SPD. Likewise, there are no reports in the literature of worsening SPD symptoms due to psychostimulant treatment in patients without ADHD.

We present the case of a 26-year-old college student who sought care because she could not control her scratching behavior. The patient reported starting the excoriation because she felt recurring insect bites on her skin. However, she described the itching as rapidly fading and that she continues excoriating without it. She only became aware of her behavior as she felt pain or bled. Most lesions were located on her thighs and legs. She was ashamed of her injuries and hid them by avoiding short clothes. Her dermatologist had already tried unsuccessfully to treat her SPD with fluoxetine and sertraline. Although she did not spontaneously self-report inattention and impulsivity symptoms, her family and friends frequently complained about them. The patient met DSM-5 criteria for both SPD and ADHD, and her husband and mother confirmed symptoms at clinically significant levels. We decided to treat ADHD first because of family and educational impairments and, after 1 month on 20 mg/day methylphenidate SODAS, she reported being able to focus on what she was feeling and that this aided her in inhibiting the impulse to scratch herself. She also stopped mentioning the itching sensation in her skin. After increasing MPH to 30 mg/day, she experienced further symptomatic improvement, and said that “did not even remember the injuries.”

Table 1 presents self-report questionnaires measuring depression, anxiety, impulsivity traits and ADHD symptoms at baseline and when using 20 and 30 mg of MPH. These scores show that changes in inattention were most consistent with SPD decrease. During follow up assessments, the patient reported that her mood improved as her academic performance and social relations became less impacted by her ADHD. Although her Beck Depression Inventory scores decreased during treatment, her initial scores were already below the cutoff for clinical depression. The patient suspended medication by herself twice after the third month and resumed excoriating her skin, which again remitted with therapy.

Table 1. Scores for depression, anxiety, impulsivity, inattention and hyperactivity questionnaires during treatment.

	No medication	MPH SODAS 20mg	MPH SODAS 30mg
BDI	8	2	0
ASRS D	8	1	1
ASRS HI	3	0	0
BIS AT	22	22	21
BIS PLAN	36	35	29
BIS MOT	24	24	22
BIS TOT	84	81	72
STAI T	55	55	55
STAI S	62	62	60

ASRS D = Adult Self Report Scale – Inattention Symptoms; ASRS HI = Adult Self Report Scale – Hyperactivity and Impulsivity Symptoms; BDI = Beck Depression Inventory; BIS AT = Barratt Impulsiveness Scale – Attentional Subscale; BIS MOT = Barratt Impulsiveness Scale Motor Subscale; BIS PLAN = Barratt Impulsiveness Scale – Planning Subscale; BIS TOT = Barratt Impulsiveness Scale – Total Score; STAI S = State-Trait Anxiety Inventory – State Score; STAI T = State-Trait Anxiety Inventory – Trait Score.

Given the low efficiency of available pharmacologic agents for treating SPD (N-acetylcysteine, SSRIs), MPH might be an option for a subset of SPD patients. Since SPD can be defined as a repetitive behavior disorder due to impulsivity and inhibitory control deficits, and considering that the patient in this case report noticed that her scratching behavior was associated with mind wandering (inattention), we can suggest some hypothesis why the ADHD treatment helped improve SPD symptoms. Methylphenidate acts by inhibiting dopamine and noradrenaline reuptake, mainly in the striatum body, prefrontal cortex and nucleus accumbens. Thus, it can be posited that its action on prefrontal cortex could have helped reduce impulsivity, whereas its action on striatum body could have increased the attentional state. Thus, we suggest that increased attention span and decreased impulsivity could be mechanisms that, when achieved jointly, could decrease SPD symptoms. Further studies are needed to address whether methylphenidate benefits SPD individuals who do not have ADHD by improving cognitive functions (e.g. inattention or inhibitory control).

Disclosure

The authors report no conflicts of interest.