Chronic Prurigo patients do not report higher impulsiveness or more traumatic life experiences than chronic pruritus patients with non-lesional skin.

Dear editor,

Pruritus has been defined as an irritating sensation of the skin, associated with the desire to scratch. However, there are notable clinical differences between pruritus patients: chronic prurigo (CPG) is a chronic pruritic condition associated with extensive scratching, which leads to the development of the typical pruriginous lesions. In the classification of the International Forum for the Study of Itch (IFSI), CPG is therefore classified in group III ‘Chronic Pruritus with chronic scratch lesions’. On the other hand, patients in IFSI group II have generalized pruritus with non‐lesional skin, but the reasons for this difference are still poorly understood and need further elucidation.

Up to now, the role of motor impulsiveness and less self‐control, possibly resulting from traumatic life experiences, on scratching activity in CPG patients has not been investigated. In other chronic conditions, e.g. chronic pain, a higher prevalence of traumatic life experiences has been reported. ,

Therefore, we intended to investigate whether impulsiveness and traumatic life experiences are more common in patients who scratch extensively (here CPG) when compared to patients with chronic pruritus (CP) on non‐lesional skin.

One hundred twenty patients with chronic prurigo (IFSI group III; 60 male and 60 female) were compared to 120 patients with chronic pruritus from IFSI group II (60 male and 60 female). The patients were selected from the database of the Center of Chronic Pruritus and addressed by mail.

After informed consent, all subjects filled in questionnaires regarding sociodemographic aspects, the Childhood Trauma Questionnaire (CTQ), the Trauma History Questionnaire (THQ) and the Baratt Impulsiveness Scale (BIT). They answered seven questions regarding their scratching or skin manipulating behaviour (a–f in Table 1) and were asked to assess their average pruritus in the last 24 h between 0 (none) and 10 (maximum pruritus) on a Visual Analogue Scale.

Table 1

Sample characteristics and characteristics of pruritus/scratching behaviour in Chronic Prurigo (CPG) and Chronic Pruritus (CP) patients

	Chronic Prurigo (CPG) (n = 120)		Chronic Pruritus (CP) (n = 120)		Statistics
					T‐test
	Mean	SD	Mean	SD	T		P
Age	61.98	11.3	62.07	11.3	‐0.06		0.950
Average pruritus intensity in the last 24 h (Visual Analogue Scale; 0–10)	4.77	2.8	4.39	2.5	1.08		0.281
					Chi‐square test
Sociodemographic characteristics	n	%	n	%	Chi‐square	df	P
Family status: married	80	66.7	91	75.8	2.46	1	0.117
Education level: high school degree	18	15	27	22.5	2.22	1	0.137
Professionally working	37	30.8	42	35.0	0.47	1	0.492
Scratching behaviour
Scratch, rub etc? a	115	95.8	100	83.3	10.05	1	0.002
Remove bumps/impurities? b	102	85.0	53	44.2	43.74	1	0.001
Harm your skin till scars develop? c	105	87.5	51	42.5	53.41	1	0.001
Relief by scratching? d	94	78.3	79	65.8	4.66	1	0.031
Several hours/d? e	43	35.8	27	22.5	5.16	1	0.023
Obsessive/ compulsive? f	71	59.2	41	34.2	15.07	1	0.001
Social conflicts? g	38	31.7	10	8.3	20.42	1	0.001

Do you repeatedly scratch, rub, touch or sting the itching skin?

Do you intend to remove small bumps or impurities by doing this?

Do you harm your skin by this behaviour so that scars occur or the skin colour changes?

Do you experience joy, satisfaction or relief by scratching, rubbing, touching or stinging your skin?

Does this sometimes keep you occupied for several hours a day?

Do you have the impression that this behaviour is obsessive/compulsive?

Does this behaviour lead to anger or conflicts with your family or friends? Did it lead to problems at your working place?

Bold indicate significant results (P‐value < 0.05).

Chronic prurigo and CP patients did not differ significantly in sociodemographic characteristics and age. Although CPG and CP patients reported comparable itch intensity, the self‐reports on scratching differed significantly between CPG and CP (Table 1).

The overall impulsiveness and most of the BIS‐subscales (especially motor impulsiveness and self‐control) were not significantly different between CPG and CP. Only the subscale ‘cognitive instability’ was significantly higher in CP than in CPG (Table 2). Also, there were no significant differences between chronic pruritus and chronic prurigo patients regarding the number of traumatic life experiences (Table 2).

Table 2

Impulsiveness and traumatic life experiences in Chronic Prurigo (CPG) and Chronic Pruritus (CP) patients

	Chronic Prurigo		Chronic Pruritus		Statistics T‐test
Barratt Impulsiveness scale (BIS) Higher scores = higher impulsiveness	Mean	SD	Mean	SD	T	P
Attention (5–20)	10.30	2.6	10.62	2.3	−1.02	n.s.
Motor impulsiveness (7–28)	13.25	3.1	13.72	2.9	−1.21	n.s.
Self‐control (6–24)	12.63	3.6	12.22	3.0	0.99	n.s.
Cognitive complexity (5–20)	12.45	2.1	12.40	1.9	0.19	n.s.
Perseverance (4–16)	7.25	1.4	7.21	1.5	0.21	n.s.
Cognitive instability (3–12)	5.25	1.6	5.94	1.5	−3.48	0.001
BIS‐Sum (range 30–120)	61.13	8.6	62.11	7.7	−0.92	n.s.
Childhood Trauma Questionnaire (CTQ)
Emotional abuse	7.70	3.9	8.23	4.1	−1.02	n.s.
Physical abuse	6.60	3.2	6.62	2.8	−0.05	n.s.
Sexual abuse	5.31	1.4	5.28	1.3	0.19	n.s.
Emotional deprivation	10.74	4.6	10.70	4.7	0.07	n.s.
Physical deprivation	7.99	2.8	8.06	3.0	−0.19	n.s.
CTQ‐Sum (range 25–125)	38.33	11.8	38.87	11.6	−0.36	n.s.
Trauma History Questionnaire (THQ)
Crimes (0–4)	0.36	0.7	0.47	0.8	−1.09	n.s.
General catastrophes and trauma (0–13)	2.46	2.1	2.54	1.8	−0.33	n.s.
Physical and sexual trauma (0–6)	0.34	0.7	0.43	1.0	−0.79	n.s.
THQ‐Sum (range 0–23)	3.33	2.9	3.63	2.8	−0.83	n.s.

In order to predict the membership in the CPG or CP group, we entered the previously hypothesized explaining variables BIS‐motor impulsiveness, BIS‐self‐control, CTQ and THQ total scores into a discriminant analysis, which resulted in the following statistics: eigenvalue 0.017; canonic correlation 0.018; Wilk’s lambda 0.08; and chi‐square for Wilk’s lambda 3.90; P < 0.420. These and the classification result (only 55.1% of the patients were correctly classified as CP or CPG, while the a priori probability for the subgroup membership was 50%) showed no significant contribution of the independent variables for the category CPG or CP.

As a conclusion, we found no evidence that more traumatic life events and/or higher motor impulsiveness/lower self‐control are associated with the extensive scratching in CPG and resulting in the development of the typical chronic prurigo lesions.

Whether traumatic experiences are more common in CP and/or CPG when compared to population, samples cannot be answered from our data, as our study did not include a general population control group. Also, impulsiveness was measured by a self‐report scale which might not be specific enough for pruritus patients, not by objective behavioural measures. Also, the trauma history was self‐reported and might be affected by inaccurate memories. On the other hand, police or trial records would be affected by the many cases which are never reported.

Conflict of interest

Gudrun Schneider, Reinhold Steinbach and Astrid Stumpf have nothing to disclose. Sonja Ständer reports personal fees from Almirall, personal fees from Beiersdorf, personal fees from Bellus Health, personal fees from Cara Therapeutics, personal fees from Celgene, personal fees from Galderma Laboratorium, personal fees from Clexio Biosciences, personal fees from LEO, personal fees from Menlo Therapeutics, personal fees from Novartis, personal fees from Sienna Biopharmaceuticals, personal fees from Trevi Therapeutics, personal fees from Vanda Pharmaceuticals, other from Dermasence, other from Kiniksa, other from Galderma, personal fees from Galderma S.A., other from Menlo Therapeutics, other from Novartis and other from Trevi Therapeutics, outside the submitted work.