Patterns of Skin Picking in Skin Picking Disorder: Ecological Momentary Assessment Study
Authors: Gallinat Christina , Moessner Markus , Wilhelm Maximilian , Keuthen Nancy , Bauer Stephanie 
Published: May 2024

Background
Skin picking disorder (SPD) is an understudied mental illness that is classified as a body-focused repetitive behavior disorder. Literature suggests that pathological skin picking is strongly integrated into the daily lives of affected individuals and may involve a high degree of variability in terms of episode characteristics, frequency, and intensity. However, existing data on the phenomenology of SPD are limited and typically involve retrospective assessments, which may fail to accurately capture the behavior’s variability.

Objective
This study aimed to investigate skin picking in the daily lives of individuals with SPD by using ecological momentary assessment (EMA). The first aim focused on the description of skin picking patterns (eg, characteristics, intensity, and distribution of episodes and urges), and the second aim explored differences in characteristics and patterns between automatic and focused skin picking.

Methods
Participants were recruited online and underwent a web-based screening, a diagnostic telephone interview, and a comprehensive online self-report questionnaire before participating in an EMA protocol. The latter included 10 consecutive days with 7 pseudorandom, time-contingent assessments per day between 8 AM and 10 PM. The EMA questionnaire assessed the current skin picking urge, the occurrence of the behavior, and a detailed assessment of the episodes’ characteristics (eg, length, intensity, and consciousness) if applicable.

Results
The final sample consisted of 57 participants, who completed at least 70% of the scheduled assessments (n=54, 94.7% female: mean age 29.3, SD 6.77 years). They completed 3758 EMAs and reported 1467 skin picking episodes. Skin picking occurred frequently (mean 2.57, SD 1.12 episodes per day and person) in relatively short episodes (10-30 min; 10 min: nepisodes=642, 43.8%; 20 min: nepisodes=312, 21.3%; 30 min: nepisodes=217, 14.8%), and it was distributed quite evenly throughout the day and across different days of the week. Focused and automatic episodes were relatively balanced across all reported episodes (focused: nepisodes=806, 54.9%) and over the course of the day. The analyses showed statistically significant differences between self-reported triggers for the different styles. Visual or tactile cues and the desire to pick the skin were more important for the focused style (visual or tactile cues: mean focused style [Mf]=4.01, SD 0.69 vs mean automatic style [Ma]=3.47, SD 0.99; P<.001; SMD=0.64; desire to pick: Mf=2.61, SD 1.06 vs Ma=1.94, SD 1.03; P<.001; SMD=0.82), while boredom and concentration problems were more prominent in automatic skin picking (boredom: Mf=1.69, SD 0.89 vs Ma=1.84, SD 0.89; P=.03; SMD=–0.31; concentration problems: Mf=2.06, SD 0.87 vs Ma=2.31, SD 1.06; P=.006; SMD=–0.41).

Conclusions
These results contribute to an enhanced understanding of the phenomenology of SPD using a more rigorous assessment methodology. Our findings underscore that picking can impact affected persons multiple times throughout their daily lives.

Trial Registration
German Clinical Trials Register DRKS00025168; https://tinyurl.com/mr35pdwh