Dysfunctional beliefs associated with hair pulling disorder: an examination in clinical versus non-clinical groups

Figures & data

Table 1. Summary demographic and clinical characteristics among clinical (n = 20) and non-clinical (n = 43) participants.

Variable	HPD n (%)	Non-clinical n (%)
Gender
Female	18 (90)	36 (83.7)
Male	2 (10)	7 (16.3)
Employment status^a
Employed	14 (70)	12 (28)
Unemployed	4 (20)	0 (0)
Studying full-time	2 (10)	31 (72)
Education
Secondary college	4 (2)	13 (30.2)
Vocational or higher degree	16 (80)	30 (69.8)
Relationship status
Single	14 (70)	19 (44.2)
In a relationship	6 (30)	24 (55.8)
Nationality^b
Australia	13 (65)	28 (65.1)
United Kingdom and Europe	4 (20)	5 (11.6)
Other	3 (15)	10 (23.3)
MINI diagnosis
No diagnosis (excludes TTM)	3 (15)	31 (72.1)
Any mood disorder (depression, bipolar)	14 (70)	11 (25.6)
Any anxiety disorder	9 (45)	1 (2.3)
Alcohol abuse disorder	0 (0)	1 (2.3)

MINI diagnoses do not add to 100% as comorbidities were counted.

^aCategories for Fisher’s exact test were 1 = employed (full-time or part-time/casual) and 0 = unemployed or full-time student.

^bCategories for Fisher’s exact test were 1 = Australia and 0 = all other nationalities (United Kingdom, Europe, South America, South East Asia, India, South Africa).

Table 2. Details of HPD symptoms, severity, and impact during the preceding 6 months (n = 20).

Variable	Median (range)	n (%)
Symptom characteristics
Age at symptom onset	12 (5–20)
Number of hair pulling sites	2 (0–5)
Longest number of days without hair pulling	4.5 (0–181)
Typical duration (mins) of hair pulling episodes	40 (0–350)
Typical duration (mins) thinking about hair pulling	62.5 (1–610)
Level of distress
None-to-mild		5 (25)
Moderate-to-severe		10 (50)
Severe-to-extreme		5 (25)
Functional impairment
None-to-mild		12 (60)
Moderate-to-severe		6 (30)
Severe-to-extreme		2 (10)

Information gathered via the Diagnostic Interview for HPD (Rehm & Nedeljkovic), unpublished.

Table 3. Correlations (partial correlations) between the BiTS, MGHHPS, MIST-A, and DASS-21 scores in the clinical sample (n = 20).

	MGHHPS	MIST-A-F	MIST-A-A	DASS-21-D	DASS-21-A
BiTS-NSB	.48* (.58*)	.71** (.48*)	.01 (.24)	.56**	.49*
BiTS-LCE	.48* (.51*)	.68** (.53*)	−.01 (.14)	.43	.38-
BiTS-P	.41 (.45)	.60** (.35)	.14 (.36)	.48*	.44
RSE	−.46* (−.54*)	−.52* (−.19)	.09 (−.07)	−.61**	−.41
OBQ-PC	.23 (.24)	.63** (.41)	.11 (.33)	.43	.48*
UPPS-URG	.24 (.25)	.60** (.33)	−.11 (.03)	.63**	.37
AAQ-II	.42 (.53*)	.73** (.53*)	−.14 (.05)	.49*	.57**
M (SD)	15.10 (5.94)	50.65 (14.22)	26.35 (7.86)	5.75 (4.12)	5.90 (5.79)

BiTS = Beliefs in Trichotillomania Scale; NSB = Negative Self Beliefs subscale; LCE = Low Coping Efficacy subscale; p = Perfectionism subscale; RSE = Rosenberg Self-Esteem Scale; OBQ-PC = Obsessive Beliefs Questionnaire – Perfectionism/Certainty subscale; AAQ-II = Acceptance and Action Questionnaire-II; UPPS-URG = Negative Urgency subscale; DASS-21-D = Depression, Anxiety, Stress Scale Depression subscale; DASS-21-A = Anxiety subscale.

Partial correlations (featured in parentheses) are controlling for DASS-21-D and DASS-21-A scores.

*p < .05; **p < .01.

Table 4. Means, (standard deviations) and Cronbach’s alpha coefficients for BiTS subscales and total scales in the clinical and control groups.

	HPD (n = 20)		Non-clinical (n = 43)
	M (SD)	α	M (SD)	α
BiTS-NSB	4.74 (1.64)	0.92	2.12 (0.98)	0.72
BiTS-LCE	4.16 (1.34)	0.87	2.30 (0.95)	0.76
BiTS-P	4.87 (1.30)	0.88	3.09 (1.41)	0.77
BiTS total	4.51 (1.29)	0.94	2.40 (0.89)	0.86

BiTS = Beliefs in Trichotillomania Scale; NSB = Negative Self Beliefs; LCE = Low Coping Efficacy; p = Perfectionism. All subscales scored as a mean on a 1–7 Likert scale.

Table 5. Inter-correlations between BiTS subscales for clinical (below the diagonal) and non-clinical (above the diagonal) groups.

	1.	2.	3.	4.
1. BiTS-NSB	–	.61**	.57**	.85**
2. BiTS-LCE	.80**	–	.53**	.87**
3. BiTS-P	.62**	.49*	–	.80**
4. BiTS total	.95**	.92**	.73**	–

BiTS = Beliefs in Trichotillomania Scale; NSB = Negative Self Beliefs subscale; LCE = Low Coping Efficacy subscale; p = Perfectionism subscale.

BiTS-NSB, BiTS-LCE and BiTS total scores for non-clinical participants are square root transformed.

**p < .001; *p < .05.

Table 6. Correlations between the BiTS subscales and other constructs for clinical and non-clinical groups.

			HPD (n = 20)					Non-clinical (n = 43)
	BiTS-NSB	BiTS-LCE	BiTS-P	M	SD	BiTS-NSB	BiTS-LCE	BiTS-P	M	SD
RSE	−.89**	−.65**	−.65**	16.20	6.48	.60**	.63**	.24	23.65	4.65
OBQ-PC	.59**	.48*	.82**	70.60	21.04	.65**	.58**	.75**	47.28	18.76
AAQ-II	.80**	.82**	.75**	46.70	11.01	.73**	.51**	.40**	25.12	8.39
DTS	−.78**	−.75**	−.74**	2.52	0.94	−.52**	−.55**	−.62**	3.78	0.77
ACQ-R	−.75**	−.79**	−.64**	29.90	15.05	−.53**	−.49**	−.42**	51.14	9.77
DERS	.86**	.79**	.78**	105.55	30.59	.71**	.45**	.44**	67.51	17.04
UPPS-URG	.75**	.83**	.54**	2.78	0.66	.39*	.33*	.21	2.21	0.51
UPPS-PREM	.16	.38	−.20	1.93	0.36	−.16	−.00	−.47**	2.14	0.45
UPPS-PERS	.71**	.77**	.32	2.38	0.41	.19	.32*	−.12	2.14	0.39

BiTS-NSB = Beliefs in Trichotillomania Scale Negative Self Beliefs subscale; BiTS-LCE = Low Coping Efficacy subscale; BiTS-P = Perfectionism subscale; RSE = Rosenberg Self-Esteem Scale; OBQ-PC = Obsessive Beliefs Questionnaire – Perfectionism/Certainty subscale; AAQ-II = Acceptance and Action Questionnaire-II; DTS = Distress Tolerance Scale; ACQ-R = Anxiety Control Questionnaire – Revised; DERS = Difficulties in Emotion Regulation Scale; UPPS-URG = Negative Urgency subscale; UPPS-PREM = Premeditation (lack of) subscale; UPPS-PERS = Perseverance (lack of) subscale.

For non-clinical participants, square root transformation were applied to BiTS-NSB, BiTS-LCE, RSE, and UPPS-PREM data; and logarithmic transformations were applied to AAQ-II and DERS data.

The largest correlations between the BiTS subscales and measures of construct validity are emboldened.

**p < .001; *p < .05.

Data availability statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to ethical reasons.