Table 1.

Description of former studies examining comorbidity in HPD.

Reference	Sample Size	Recruitment	Assessment
Christenson, Mackenzie, & Mitchell, 1991	60	Referrals from outpatient or respondents to newspaper ads. Study completed at a trichotillomania specialty clinic.	Semi-structured interview based on DSM-III-R for HPD and comorbid disorders
Swedo & Leonard, 1992	43	Participants who had presented for research studies at the National Institutes of Mental Health	Schedule for Affective Disorders and Schizophrenia – Lifetime Version and the Diagnostic Interview for Children and Adolescents (Based on DSM-III-R)
Schlosser, Black, Blum, & Goldstein, 1994	22	Participants recruited through a psychiatric outpatient clinic (N = 8) and newspaper advertisements (N = 14)	Semi-structured interview focused on hair pulling, Diagnostic Interview Schedule for Axis I Disorders, and Structured Interview for DSM-III-R Personality Disorders
Christenson, 1995	186	Patients presented at a Trichotillomania Clinic	Minnesota Trichotillomania Assessment Inventory based on DSM-III-R
van Minnen, Hoogduin, Keijsers, Hellenbrand, & Hendrik, 2003	43	Recruited through television ads. Self-referred to university outpatient clinic.	SCID for DSM-IV
Keijsers, van Minnen, Hoogduin, Klaassen, Hendriks, & Tanis, 2006	28	Waitlist control group from van Minnen et al., 2003	SCID for DSM-IV
Lochner et al., 2005	54	Referred to the research unit from a wide range of sources (e.g., OCD Association of South Africa, community-based primary care practitioners, and psychiatrists).	Semi-structured clinical interview and SCID-I
Diefenbach, Tolin, Hannan, Crocetto, & Worhunsky, 2005	28	Recruited for participation in treatment study	TDI and SCID
Woods, Wetterneck, & Flessner, 2006	28	Unclear	SCID
Odlaug & Grant, 2008	24	Recruited from ongoing pharmacological treatment studies and a longitudinal study on impulse control disorders	SCID-I and semi-structured interview
Grant, Odlaug, & Kim, 2009	50	Recruited through newspaper ads and referrals from medical providers	Physician-administered TDI and SCID
Lochner, Seedat, & Stein, 2010	80	Referred to the research unit from a wide range of sources (e.g., OCD Association of South Africa, community-based primary care practitioners, and psychiatrists).	SCID-I/P, SCID-II/P, SCID-OCSD, and Trichotillomania Behaviour Profile
Odlaug, Kim, & Grant, 2010	70	Participants recruited from completed clinical trials	SCID and SCID-compatible modules for impulse control disorders
Keuthen et al., 2012	38	Unclear	Semi-structured interviews for DSM-IV diagnoses. Minimum MGH-HPS score of 10, HPD symptoms for at least 1 year
Lochner, Grant, Odlaug, Woods, Keuthen, & Stein, 2012	84	Self-referred to specialty clinics	SCID-I/P for DSM-IV and proposed DSM-5 criteria
Tung, Flessner, Grant, & Keuthen, 2015	153	Participants recruited for two research studies at Massachusetts General Hospital.	SCID for DSM-IV-TR Axis I Disorders Non-Patient Edition (SCID-I/NP) and Keuthen Diagnostic Inventory for Skin Picking (K-DISP)