Automatic and focused hair pulling in trichotillomania: Valid and useful subtypes?

Area of Science:

• Psychiatry
• Clinical Psychology
• Behavioral Science

Background:

• Trichotillomania (hair-pulling disorder) has been theorized to comprise four subtypes based on the automaticity and focus of pulling behaviors.
• Previous research suggested these subtypes could inform clinical understanding and treatment.

Purpose of the Study:

• To evaluate the validity and clinical utility of a proposed four-subtype model of trichotillomania using the Milwaukee Inventory for Subtypes of Trichotillomania-Adult Version (MIST-A).
• To determine if k-means clustering of MIST-A scores could identify distinct subtypes.

Main Methods:

• 238 adults with trichotillomania completed clinical and cognitive assessments, including the MIST-A.
• K-means clustering was used to identify potential subtypes, and a four-subtype model was force-fitted based on prior literature.
• Demographic variables, age at onset, illness duration, symptom severity, and comorbid conditions were compared across the force-fitted subtypes.

Main Results:

• K-means clustering did not yield a clear cluster solution from the MIST-A data.
• The force-fitted four subtypes did not significantly differ on most demographic and clinical variables.
• The high-focused/high-automatic subtype showed worse symptom severity, and specific subtypes had higher rates of comorbid depression, but overall validity was questionable due to inconsistent findings.

Conclusions:

• The MIST-A subtyping approach for trichotillomania, based on automatic and focused pulling, lacks empirical support and clinical utility.
• Findings suggest that automatic and focused pulling may coexist within individuals and episodes, rather than defining distinct subtypes.
• Further research should consider focused and automatic pulling as continuous dimensions rather than discrete subtypes.