Psoriatic itch from the patients’ perspective: a cross-sectional study

Introduction

Psoriasis is a common chronic inflammatory disease that affects skin, nails and joints. Typical lesions involve sharply demarcated erythematous plaques covered by silvery scales on the extensor surfaces of forearms and shins, periumbilical, perianal regions, and scalp. Nail involvement occurs in about 50% of psoriasis patients, while psoriatic arthritis is present in up to 30% of all affected subjects. The manifestations of the disease are the consequence of dysregulated interactions between innate and adaptive immunity, where tumor necrosis factor-α (TNF-α) and the interleukin-23/T helper cell 17 axes play the central role [1].

The subjective symptoms of the disease include itch, irritation, burning, sensitivity, and pain [2]. Itch is recognized as the most burdensome symptom of psoriasis [3]. The visible nature of the lesions can cause stigmatization, exert a negative impact on sexual life [4] and even lead to suicidal ideations [5]. Compared to other chronic diseases involving cancer, congestive heart failure, and myocardial infarction, only chronic lung diseases and depression influenced quality of life more than psoriasis [6].

Aim

The present study aimed to investigate the impact of itch on the prevalence and severity of anxiety, depression, quality of life, and stigmatization in psoriasis patients.

Material and methods

The studied population included 106 patients recruited from the private practice, the Department of Dermatology, Venerology, and Allergology of the Wroclaw Medical University in Wroclaw, Poland, and the Department of Dermatology at the University Hospital in Krakow, Poland, between March 2023 and January 2024. The study was performed in accordance with guidelines for human studies and the World Medical Association of Helsinki (KB-234/2023, date of approval: 09.03.2023).

Every patient underwent a thorough dermatological clinical examination. Psoriasis was diagnosed based on clinical criteria. The severity of psoriasis was evaluated using the Psoriasis Area and Severity Index (PASI) [7]. Shortly after the physical examination, participants were asked to complete a specially designed questionnaire that included demographic data as well as itch and psychometric assessments. The worst itch intensity during the past week was evaluated using an 11-point Numerical Rating Scale (NRS) and the 4-Item Itch Questionnaire (4-IIQ) [8, 9]. The interpretation of the NRS score was the following: mild itch (1–-3 points), moderate itch (4–6 points), severe itch (7–8 points), and very severe itch (ł 9 points) [8]. 4-IIQ is an instrument that measures the extent, severity, frequency, and sleep disturbances due to chronic itch [9].

To assess the burden of itch, all subjects were asked to fulfill several questionnaires, including the Hospital Anxiety and Depression Scale (HADS), Generalized Anxiety Disorder-7 (GAD-7), Patient Health Questionnaire-9 (PHQ-9), Dermatology Life Quality Index (DLQI) and 6-Item Stigmatization Scale (6-ISS).

The Hospital Anxiety and Depression Scale (HADS) is a standardized self-assessment instrument designed to measure the symptoms of anxiety (HADS Anxiety, HADS-A) and depression (HADS Depression, HADS-D) in clinical settings. The questionnaire consists of 14 items, with 7 items addressing anxiety symptoms and 7 items addressing depression symptoms. Each item is scored on a 4-point scale, ranging from 0 to 3 points, resulting in a maximum total score of 42 points. The maximum score for each subscale is 21 points. The abnormal overall score is 11 points, while a score of 8 points or greater on either the anxiety or depression subscale indicates a potential clinical diagnosis of the respective condition [10].

The Generalized Anxiety Disorder-7 (GAD-7) is a screening tool for generalized anxiety disorder. The questionnaire comprises 7 items that evaluate the frequency of anxiety symptoms experienced during the past 2 weeks. Each item is scored on a 4-point scale, where 0 points are assigned for “not at all”, 1 point for “several days”, 2 points for “over half the days”, and 3 points for “nearly every day”. The total score is calculated by summing the scores from all 7 items, resulting in a possible range of 0 to 21 points. The interpretation of the GAD-7 score is as follows: minimal anxiety (0–4 points), mild anxiety (5–9 points), moderate anxiety (10–14 points), and severe anxiety (15–21 points) [11].

The Patient Health Questionnaire-9 (PHQ-9) is a 9-item screening instrument designed to assess the severity of depressive symptoms. It is based on the diagnostic criteria for major depressive disorder as outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). For each of the 9 items, the patient rates the frequency of the corresponding symptoms of depression experienced over the past 2 weeks on a 4-point scale, ranging from 0 (“not at all”) to 3 (“nearly every day”). The total score is calculated by summing the scores for all 9 items, resulting in a possible range of 0 to 27 points. The interpretation of the PHQ-9 total score is as follows: minimal depression (0–4 points), mild depression (5–9 points), moderate depression (10–14 points), moderately severe depression (15–19 points), and severe depression (20–27 points). A cut-off score of 10 or greater on the PHQ-9 has been found to have 88% sensitivity and specificity for the diagnosis of major depressive disorder [12].

The Polish version of the Dermatology Life Quality Index (DLQI) questionnaire was utilized to evaluate the patient’s quality of life (QoL). The DLQI consists of 10 items covering different aspects of the patient’s life over the past week, including symptoms and feelings, daily activities, leisure, work and school-related matters, personal relationships, and treatment side effects. Each item is scored on a 4-point scale, where 0 represents “not at all”, 1 means “a little”, 2 represents “a lot”, and 3 represents “very much”. The individual scores are then summed to calculate the total DLQI score, ranging from 0 to 30 points. The interpretation of the total DLQI score was the following: minimal impact on QoL (0–1 points), small impact on QoL (2–5 points), moderate impact on QoL (6–10 points), large impact on QoL (11–20 points) and extremely large impact on QoL (21–30 points) [13].

The 6-Item Stigmatization Scale (6-ISS) is a dermatology-specific tool utilized to evaluate stigmatization experienced by patients due to their skin disease. The questionnaire comprises 6 questions that assess different dimensions of stigmatization, including anticipation of rejection, feelings of being flawed, sensitivity to the opinions of others, guilt and shame, negative attitudes, and secretiveness. The patient answers each question on a 4-point scale, where 0 points represent “not at all”, 1 point represents “sometimes”, 2 points represent “very often”, and 3 points represent “always”. The total score is calculated by summing the scores from all items, resulting in a possible range of 0 to 18 points [14, 15].

Results

The study population comprised 106 adults with psoriasis, including 36 (34.0%) women and 70 (66.0%) men, with an age range of 18–72 (mean: 42.07 ±12.96) years. The mean PASI score was 10.93 ±8.47 points. The average disease duration was 14.89 ±12.69 years, ranging from 1 to 55 years. Out of 106 subjects, 90 (84.9%) experienced itch during the past week, with a mean intensity of 4.52 ±2.88 points in the NRS score. 25 (27.8%) adults with psoriasis reported mild itch, 34 (37.8%) of them experienced moderate itch, while 25 (27.8%) had severe and 6 (6.7%) very severe itch. The prevalence of women with itch was significantly higher than men (35 (97.2%) vs. 55 (78.6%), p = 0.011). Additionally, according to the NRS, women experienced itch of significantly higher intensity compared to men (5.69 ±2.51 points vs. 3.91 ±2.89 points, p = 0.003). Moreover, the distribution of itch severity was significantly different between both genders (p = 0.023). Analyzing itch severity cut-offs, more severe itch was reported also more commonly in female patients compared to males. The mean 4-IIQ was 6.79 ±4.37 points, with no significant difference between women and men. The data are presented in Table 1.

The mean total HADS score for the entire studied population was 10.4 ±7.47 points, with females exhibiting significantly higher scores (13.1 ±7.93 points) than males (9.0 ±6.86 points; p = 0.005). Regarding the assessment of anxiety, the mean HADS-A value was 6.25 ±4.52 points, and the average GAD-7 score was 6.01 ±5.16 points in the whole cohort. Women scored significantly higher on both the HADS-A (8.42 ±4.85 points vs. 5.14 ±3.9 points; p < 0.001; Mann-Whitney U test) and the GAD-7 (7.50 ±5.58 points vs. 5.24 ±4.79 points; p = 0.036; Mann-Whitney U test) than men. Regarding the assessment of depression, the mean HADS-D score was 4.14 ±3.68 points, and the average PHQ-9 score was 6.86 ±5.98 points in the whole population. A statistically significant difference was observed between females and males on the PHQ-9 (7.50 ±5.58 points vs. 5.24 ±4.79 points, p = 0.021; Mann-Whitney U test) but not on the HADS-D. Concerning the assessment of QoL and stigmatization, the mean DLQI was 8.09 ±6.99 points, and the average 6-ISS was 4.72 ±3.63 points. No statistically significant differences were noted between females and males for these parameters (Table 2).

Psoriasis patients who reported itch in the past week scored significantly higher in HADS total score (11.06 ±7.69 points) and had a higher prevalence of HADS abnormal score (26 (28.9%)) than the rest of the studied group (6.69 ±4.72 points, p = 0.037; 1 (6.3%), p = 0.037 respectively; Mann-Whitney U test). Individuals with itch had significantly more impaired QoL than those without itch (8.90 ±7.01 points vs. 3.56 ±4.95 points, p < 0.001; Mann-Whitney U test) and the distribution of QoL was significantly different between patients with and without itch (p < 0.001). There was no significant difference in the assessments of anxiety, depression, and stigmatization between individuals reporting itch and the rest of the participants (Tables 3, 4).

The intensity of itch, as measured by NRS, correlated significantly with the HADS total score (r = 0.234; p = 0.027), GAD-7 (r = 0.279; p = 0.008), PHQ-9 (r = 0.213; p = 0.044), and DLQI (r = 0.336; p = 0.001) (all assessed with Spearman’s correlation). No relationship between itch severity and stigmatization was found. Additionally, in the subgroups of itch intensity, there were significant differences in HADS total score (p = 0.017), GAD-7 (p = 0.01), and DLQI (p = 0.003) (assessed with Kruskal-Wallis one-way analysis of variance on ranks). Patients with more severe itch experienced a higher psychosocial burden (Table 5). The multivariate analysis of variance (MANOVA) revealed that itch significantly influenced HADS (p = 0.003), GAD7 (p = 0.003), and DLQI (p < 0.001) scores but did not influence PHQ-9 (p = 0.075) and 6-ISS (p = 0.094) scores.

Discussion

Numerous authors have investigated psychiatric comorbidities in psoriasis. A recent systematic review indicated that individuals with this disease were at least one and a half times more prone to the development of depression than their healthy controls, and 23% of them exhibited symptoms of depression, as estimated by the HADS questionnaires [16]. Another meta-analysis found that the prevalence of anxiety symptoms was 34% in psoriasis patients, according to HADS [17]. In our study, the severity of depression and anxiety was higher in females with psoriasis compared to males, which is consistent with the evidence from a systematic review [18]. Interestingly, the presence of psoriatic arthritis was an additional risk factor for the development of both anxiety and depression [18].

The negative impact of psoriasis on mental health has been studied for many years. In the beginning, it was considered to be a result of associated itch, visibility of lesions, shame, and stigmatization [19]. However, recent findings have identified common inflammatory pathways between psoriasis and psychiatric disorders involving anxiety and depression. Increased levels of proinflammatory cytokines such as IL-6 and TNF were found in the blood of patients with depression [20]. Moreover, a positive correlation was identified between the serum levels of IL-17 and IL-23 and the severity of anxiety and depression [21]. Another mechanism in which psoriasis can lead to depression is through hyperactivation of the hypothalamus-pituitary-adrenal (HPA) axis, which was suggested by an elevated level of IL-6 found in the central nervous system of transgenic mice in response to stress [22].

Itch is defined as an unpleasant subjective sensation that leads to scratching. The prevalence of this sensation in psoriasis ranges between 62% and 97% and is most often moderate in intensity, which is in line with our findings [3]. In our study, itch was more frequent and intense in females, consistently with other research results [2, 23]. Parts of the body most affected by this symptom include the legs, hands, back, and scalp [24]. It occurs in both lesional and non-lesional skin [24]. Aggravating factors involve stress, heating, hot water, skin dryness, sweating, bad moods, exercise, lying position, and contact with clothes, while ameliorating factors include sleep and cold showers [3, 25].

Itch exerts a significant impact on various aspects of mental health in psoriasis patients. Most of them consider itch the most important, severe, and troublesome symptom of this disease [26]. This sensation impairs sleep quality in psoriatic individuals due to scratching that can occur during the entire sleep period [27]. Consequently, sleep disturbances have a negative impact on work productivity and presenteeism [28]. Moreover, according to the study of Amatya et al. [23], itch significantly influences concentration, mood, appetite, and sexual desire and can cause suicidal ideations [5]. Additionally, vulvar itching and burning in females with psoriasis frequently leads to sexual problems [29].

In our study, the intensity of itch was associated with impaired QoL, anxiety, and depression, corresponding to previous research outcomes [27, 30, 31]. For instance, Reich et al. [30] demonstrated that psoriasis patients with itch had significantly reduced QoL and were more depressive compared to individuals without this symptom. Moreover, the intensity of this sensation correlated with DLQI, the severity of depression and the level of stigmatization [30]. In the study of Gupta et al. [32], an alteration in the severity of depression correlated with the change in itch intensity. Therefore, it was suggested that depressive symptoms reduce the threshold for itch [32]. It was also demonstrated that improvement of itch following successful psoriasis treatment with etanercept was associated with improved QoL [27].

The study limitations include the small size of the studied population. Especially the group of psoriatic patients without itch was relatively small. However, the percentage of non-itchy psoriatic patients in our cohort of studied subjects was similar to a well-known one [30]. In our opinion, based on above-mentioned issues, the comparisons between itchy and non-itchy subjects should be treated with caution. Additionally, the assessment of anxiety, depression, and stigmatization was based only on questionnaires. Therefore, a thorough psychiatric examination would be needed to confirm the diagnosis of the respective conditions. We do believe that the strength of our project was the usage of multiple questionnaires to assess both anxiety and depression.

Conclusions

Itch is a very prevalent symptom of psoriasis and is often associated with anxiety, depression and impaired QoL. Therefore, a multidisciplinary approach is needed in the management of psoriasis.