Associations with Methylphenidate Treatment in Emotion Regulation and Skin-Picking Severity in Adolescents with Attention-Deficit/Hyperactivity Disorder: A Clinical Follow-Up Study

<b>Objective</b>: To evaluate changes in emotion regulation, skin-picking disorder (SPD) severity, and repetitive thoughts and behaviors in adolescents with attention-deficit/hyperactivity disorder (ADHD) and comorbid SPD during methylphenidate treatment, and to examine the association between emotion regulation and SPD severity. <b>Materials and Methods</b>: This naturalistic follow-up study included 26 adolescents aged 11-17 years with ADHD and comorbid SPD. Participants received methylphenidate and were reassessed after three months. Emotion regulation, SPD severity, and repetitive thoughts and behaviors were assessed at baseline and follow-up using the Difficulties in Emotion Regulation Scale (DERS), Skin Picking Scale-Revised (SPS-R), and Repetitive Thoughts and Behaviors Scale-Child Form (RTBS-CF). Pre-post differences were analyzed using paired-sample tests, and associations were examined using correlation and linear regression analyses. <b>Results</b>: Significant reductions were observed in total DERS scores (<i>p</i> < 0.001, Cohen's d = 1.35) and all subscales except non-acceptance (<i>p</i> = 0.686, Cohen's d = 0.08). SPS-R and RTBS-CF scores decreased significantly (both <i>p</i> < 0.001, Cohen's d = 1.79 and 0.91, respectively). Changes in DERS scores were moderately correlated with changes in SPS-R scores (r = 0.554, <i>p</i> = 0.003). Changes in emotion regulation were significantly associated with changes in SPD severity, accounting for approximately 31% of the variance in this sample. <b>Conclusions</b>: Methylphenidate treatment was associated with significant improvements in emotion regulation and concurrent reductions in skin-picking severity in adolescents with ADHD and comorbid SPD. Given the single-arm, pre-post naturalistic design, these findings should be interpreted as associative and exploratory rather than causal.