Introduction

Psoriasis is a systemic, inflammatory, chronic disorder with predominantly skin and joint manifestations. The prevalence of psoriasis in the adult population is 3.2% in the United States of America [44]. In Malaysia, psoriasis accounts for 9.5% of all outpatient dermatology consultations [55]. The association between psoriasis and psychological distress is well-established. A meta-analysis showed that 28% of patients with psoriasis had depression, with 19% of them fulfilling the Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV) diagnostic criteria and 12% fulfilling the International Classification of Diseases (ICD) criteria [11]. Furthermore, depression is associated with poorer quality of life [16] and increased stress [2, 8, 42]. In a Singaporean study, anxiety and depression were present in 34 and 9.7% of individuals with psoriasis, respectively [60]. Psychological complications and social anxiety and avoidance are associated with increased disease severity, the perception of helplessness and poor social support [54]. Individuals with psoriasis have reported higher levels of anxiety, loneliness and social isolation compared to patients with leg ulcers [27]. The presence of psychological complications is also associated with poorer compliance with treatment [49]. In addition, psoriasis is associated with a higher risk of suicide compared to melanoma or cutaneous allergies [29, 42, 57].

Psoriasis also adversely impacts quality of life [16, 38, 46]. A previous Malaysian study found that psoriasis has a moderate impact on quality of life overall with one in three respondents reporting severe impairment in quality of life. Quality of life in individuals with psoriasis has been found to be associated with disease severity, marital status, employment status, nail dystrophy, involvement of exposed areas, itch, sleep disturbance, stress and infection [40]. Moderate to severe psoriasis is associated with poorer Dermatology Life Quality Index (DLQI) scores [52]. A poorer quality of life has, in turn, been found to be related to anxiety and depression in patients with psoriasis [30]. In addition to disease severity and psychological complications, stigmatization associated with psoriasis also affects quality of life [3]. Treatment of psoriasis resulting in improvement in the PASI severity score leads to improvement in quality of life [36].

While the psychological consequences of psoriasis and the negative effects of these complications on quality of life are considered to be well-established, few studies have evaluated the associations between disease severity and head or joint involvement and the psychological complications. This study was performed to evaluate the relationship between disease severity and clinical manifestations of psoriasis and psychological distress among adults with psoriasis. Furthermore, we evaluated the association between disease severity, clinical features and psychological complications with quality of life in individuals with psoriasis.

Patients and methods

Sample population

Participants of this single-center, cross-sectional study were recruited from the dermatology clinic at the University of Malaya Medical Center, Kuala Lumpur between April 2013 and January 2015 using convenience sampling. Ethical approval was obtained from the hospital medical ethics committee (MEC Ref No. 967.6). The inclusion criteria were chronic plaque psoriasis, age 18 years and above and attending the dermatology clinic for regular follow-up. All subtypes of chronic plaque psoriasis including scalp psoriasis, inverse psoriasis, sebopsoriasis and palmoplantar psoriasis were included in the study. Patients who were unable to understand or answer the questionnaires due to a language barrier or cognitive issues were excluded.

Sample size calculation

A study by Nyunt et al. [40] showed that 58.5% of subjects with severe psoriasis reported a DLQI ≥ 10 compared to 23.4% of individuals with mild to moderate psoriasis. The calculated effect size for this meaningful difference was 0.327. Therefore, accepting an alpha error of 5% and a power of 80%, an estimated sample size of 73 subjects was required (estimated 21 subjects with severe psoriasis and 52 subjects with mild to moderate psoriasis with an allocation ratio of 2.5 based on the original study) using the G*Power software program, Department of Psychology, Heinrich-Heine-Universität Düsseldorf [13]. In Nyunt et al. [40], 33.6% of subjects reported severely impaired quality of life. Accordingly, a minimum sample size of 89 subjects was, therefore, considered appropriate for the inclusion of three co-variates within our multivariate analyses [41].

Clinical characteristics

Physical examination was performed by a single assessor (ZK) to determine the Psoriasis Area and Severity Index (PASI) scores. PASI scores greater than 12 were classified as “severe”, scores of 7–12 as “moderate” and scores of less than 7 as “mild” [14, 53]. Subjects’ medical records were reviewed to identify the presence of comorbidities. Psoriatic arthropathy was defined according to the Moll and Wright definition, which involves the presence of psoriasis associated with inflammatory arthritis (peripheral arthritis and/or spondylitis) and a negative serologic test for rheumatoid factor [37].

Depression, anxiety and stress

The 42-item Depression, Anxiety and Stress Scale (DASS-42) was self-administered in the English, Malay or simplified Chinese languages [7, 12, 34, 45]. The DASS-42 is a questionnaire that has been validated in the above three languages to determine the presence and severity of psychological symptoms during the preceding week in the domains of depression, anxiety and stress using a 4-point Likert scale with 0 indicating “never” and 3 indicating “all the time”. Individual item scores were aggregated separately for each domain of stress, anxiety and depression. The Cronbach’s α values for the DASS-42 were 0.948 for depression, 0.878 for anxiety and 0.939 for stress.

The maximum score for each domain was 42, with 0 indicating no symptoms and 42 indicating extremely severe symptoms. The domain scores were then categorized into normal, mild, moderate, severe or extremely severe using established cut-off values. The cut-off values for normal, mild, moderate, severe and extremely severe for depression were 0 to 9, 10 to 13, 14 to 20, 21 to 27, and ≥ 28, respectively. The cut-off values were 0 to 7, 8 to 9, 10 to 14, 15 to 19 and ≥ 20 for anxiety and 0 to 14, 15 to 18, 19 to 25, 26 to 33 and ≥ 34 for stress, respectively [34]. The scores were further dichotomized into the presence or absence of depression, anxiety and stress; those with mild, moderate, severe and extremely severe symptoms were considered to have depression, anxiety and stress.

Quality of life

Quality of life was assessed using the Dermatology Life Quality Index (DLQI), a self-reported questionnaire specific to dermatology [15]. The DLQI consists of ten questions based on the domains of symptoms and feelings, daily activities, leisure, work and school, personal relationships and treatment over the preceding week. Responses to individual questions are scored from 0 to 3 (0 indicating ‘not at all’ and 3 indicating ‘very much’), and the total scores were calculated. Total scores ranged from 0 (no impairment) to 30 (maximum impairment). DLQI scores of ten or above were categorized as severe impairment in quality of life [40].The Cronbach’s α for the DLQI was 0.919.

Data analysis

Data analyses were conducted using Statistical Package for the Social Sciences (SPSS) version 21.0 [22]. The chi squared test was used to identify potential associations between DASS and DLQI scores with clinical factors as binary independent variables. When there were more than two categories, e.g., mild, moderate and severe for illness severity, bivariate logistic regression with dummy variables was employed using mild as the reference category. The independent t test was used for the comparison of continuous variables between the two groups. Multivariate logistic regression models were used to identify independent predictors of depression, anxiety, stress and reduced quality of life. To ensure that the data do not conflict with the assumptions made by the model, the Hosmer–Lemeshow goodness of fitness test for logistic regression was performed. Multicollinearity was investigated but was not found. All tests were two-tailed with statistical significance defined as p < 0.05.

Results

Baseline characteristics

One hundred and two subjects were recruited for this study. Two subjects did not complete the DASS-42 questionnaire and were excluded from subsequent analyses. Fifty-eight subjects (58.0%) were male. The mean age of subjects was 50.9 years (standard deviation, SD 17.7 years) while the mean age of disease onset was 38.7 years (SD 18.0 years). The median duration of psoriasis was 8.0 years [interquartile range (IQR) 5.0–15.8]. The median PASI score was 8.65 (IQR 4.3–14.6); 42 subjects (42.0%) had mild disease, 26 (26.0%) had moderate disease and 32 (32.0%) had severe disease. Twenty-three (23.0%) had psoriatic arthropathy, while 81 (81.0%) had head involvement. The clinical features according to the presence of head involvement and psoriatic arthropathy are summarized in Table 1.

Table 1 Comparison of baseline characteristics between patients with head involvement and psoriatic arthropathy
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Depression, anxiety and stress in all participants with psoriasis

Twenty-seven subjects (27.0%) reported symptoms of at least mild depression (Table 2). Thirty-seven (37.0%) had symptoms of anxiety and 25 (25.0%) had symptoms of stress. Among those who reported depression, 7 (7.0%) had mild, 13 (13.0%) had moderate, 4 (4.0%) had severe and 3 (3.0%) had extremely severe symptoms. Five participants (5.0%) reported mild, 14 (14.0%) reported moderate, 12 (12.0%) reported severe, and 6 (6.0%) reported extremely severe anxiety. Among those who had stress, 10 (10.0%) were classified as mild, 6 (6.0%) as moderate, 5 (5.0%) as severe and 4 (4.0%) as extremely severe.

Table 2 Univariate analysis for depression, anxiety, stress and severely impaired quality of life by clinical characteristics
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Clinical characteristics, psychological status and quality of life

The relationships between clinical manifestations of psoriasis and depression, anxiety, stress and quality of life are demonstrated in Table 2, while the relationships between disease severity and depression, anxiety, stress and quality of life are demonstrated in Table 3. Disease severity was not associated with the presence or absence of psychological symptoms. Subjects with severe psoriasis, however, experienced poorer quality of life compared to those with mild psoriasis (p = 0.043). Head involvement was significantly associated with depression (p = 0.018) and anxiety (p = 0.008). Depression, anxiety and stress were all associated with a higher total DLQI score (p < 0.001). Individuals with depression, anxiety, stress and reduced quality of life were significantly younger in age and had earlier onset of psoriasis (Table 3). The median PASI score was also higher in subjects with severely impaired quality of life (p = 0.014) (Table 3).

Table 3 Univariate analysis comparing depression, anxiety and stress with age, age of onset, absolute PASI scores and duration of disease
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Independent predictors of depression, anxiety and stress

Multivariate logistic regression models adjusting for confounders that were statistically significant in Tables 2 and 3 are summarized in Table 4.

Table 4 Multivariate logistic regression analyses (stepwise forward method) for depression, anxiety, stress and quality of life by clinical features
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Depression was considered the dependent variable in Models 1 and 2, anxiety was the dependent variable in Models 3 and 4, and stress was the dependent variable in Models 5 and 6. In Model 1, the relationship between age and depression was no longer statistically significant after adjusting for the presence of head involvement. In Model 2, age of onset was associated with depression even after adjusting for head involvement.

The presence of anxiety and stress was significantly associated with age after adjustment for head involvement (Models 3 and 5 respectively). For Models 4 and 6, age of onset remained significantly associated with anxiety and stress, respectively, after adjustment for head involvement.

Severely impaired quality of life as indicated by the DLQI score was considered the dependent variable in Models 7 to 10. The presence of any psychological distress or any symptoms of depression, anxiety, and stress were all associated with reduced quality of life after adjusting for age and PASI scores (Models 7–10). However, age of onset was not associated with quality of life after adjusting for severity and the presence of psychological distress, depression, anxiety or stress.

Discussion

We studied 100 adults with psoriasis to evaluate the relationship between the clinical features of the disease and psychological impact and quality of life. Presence of head involvement was significantly associated with anxiety and depression. Younger age and younger age of disease onset were predictors for anxiety, stress and reduced quality of life. Furthermore, the presence of severe disease and psychological distress were independent risk factors for reduced quality of life. However, joint involvement did not significantly affect psychological outcome or quality of life.

Involvement of skin areas that are difficult to conceal, leading to a negative effect on cosmesis, is likely to potentiate stigmatization and hence leading to negative psychological sequelae. Yang et al. [60] reported that an adverse cosmetic effect in psoriasis was associated with higher self-reported anxiety but not depression. However, a separate study found that head involvement was a significant predictor of depression but not anxiety [43]. The difference in psychological symptoms may have been due to regional variations, with the former study conducted in Asia, while the latter study was conducted in Europe. Considering other previously published studies on regional differences in psychological response to diseases, the conflicting findings of the above studies suggest that cultural factors may influence the perception of visible skin disease [23, 33, 35, 47, 61]. However, our study found that head involvement was associated with both anxiety and depression, suggesting that the differences may actually be attributed to differences in choice of questionnaires.

The absence of any significant association between joint involvement with psychological symptoms were consistent with a previous study by Carneiro et al. [5], who found that fatigue rather than joint pain was associated with disease severity and psychosocial aspects of the disease. Skoie et al. [56], however, found that fatigue was associated with poorer quality of life but not disease severity. It is of interest that the negative effects of psoriasis on appearance are more likely to be linked to psychological symptoms than the potentially disabling symptoms associated with psoriatic arthropathy. The proportions of participants with varying disease severity were equally represented within this study. The consistency in lack of association between joint symptoms and psychological sequelae in ours and previously published studies substantiates our findings. We may, therefore, hypothesize that symptoms that are less outwardly visible such as joint pain and reduction in function may not have the same negative psychological effects compared to that observed in visible and potentially disfiguring skin conditions.

Younger age was associated with increased risk of psychological sequelae. Age and maturity may lead to the development of better coping skills. In addition, acceptance of a chronic disease and the need for long-term treatment may be greater with age, with a further lower likelihood of societal stigmatization attached to facial disfigurement [6, 25, 58]. This was evidenced by a magnetic resonance imaging (MRI) study that demonstrated that patients with psoriasis who did not have anxiety or depression had diminished responses in the insular cortex to expressions of aversion when compared to healthy controls, thus protecting these individuals against the psychological complications of psoriasis [26]. Visibility of skin lesions and psoriatic joint involvement may affect social or interpersonal relationships as well as career prospects, which would be more crucial in the younger patient attempting to enter the job market or finding a long-term partner [17, 59]. However, we found that the duration of illness was not associated with psychological distress or quality of life. We can, therefore, surmise that it is the individuals’ biological age rather than the number of years they have lived with the disease that protects the individual from the psychological complications of psoriasis [25].

The limited effect of disease severity on psychological symptoms in our study is consistent with the results of other studies [51]. Richards et al. reported that perception of stigmatization was a stronger determinant of psychological distress and disability than disease severity [50]. Other studies employing different psychological assessment tools and laboratory markers of inflammation such as tumor necrosis factor-alpha (TNF-α) have suggested a link between disease severity and reduced affective expression and depression [9, 10, 32]. While disease severity was not associated with negative psychological effects, it was associated with reduced quality of life, a finding supported by previous studies [4, 20, 24, 40, 52, 58]. The rationale behind reduced quality of life and psoriasis severity may be explained by psychological distress as the relationship between PASI and reduced quality of life was attenuated by both overall psychological distress as well as presence of depressive symptoms in our study.

The presence of any psychological distress and any symptoms of anxiety, depression or stress were associated with reduced quality of life. This finding is similar to that of previously published studies globally. Depression and stress had an effect on quality of life among individuals with psoriasis in a Korean study [31], while depression and anxiety but not disease severity predicted the level of disability in individuals with psoriasis among ethnic Chinese patients in Singapore [60]. In a separate study conducted in Greece, anxiety was associated with poorer quality of life [28], while anxiety and depression were similarly associated with poorer quality of life in a study conducted in India [30]. Social anxiety is associated with pruritus, depression, stress and impaired quality of life in individuals with psoriasis [21, 48]. Social anxiety may, in turn, be attributed to internalized stigma among patients with psoriasis, which is related to severity of disease, visibility of disease, quality of life, general health perception and psychological distress [1, 18].

Our study is limited by the use of a convenience sampling method and the recruitment of patients from a single center, which may limit the generalizability of our findings. In addition, the cross-sectional design of our study also precluded the assignment of any temporal relationship and causal link between clinical features, psychological complications and quality of life. The presence and severity of symptoms such as pruritus, pain, sensitivity and fatigue were not determined in our study. Other studies have shown that pruritus is associated with depression [19], which was found to be a strong predictor of quality of life [18, 39]. Furthermore, the DASS questionnaire is unable to address the shared variance between mood and stress. In addition, the applicability of the PASI is limited to those with chronic plaque psoriasis, which, therefore, limits the relevance of our study to other dermatological manifestations. Future studies should consider evaluating the rationale underlying psychological distress in individuals with arthritis, the social stigma associated with psoriasis and head involvement, and the role of other distressing symptoms such as pruritus, pain and sensitivity associated with this skin condition.

Conclusion

Presence of head involvement was associated with increased risk of anxiety in individuals with psoriasis. Younger age appeared to be an independent risk factor for psychological complications and reduced quality of life. Furthermore, disease severity and psychological distress were associated with impaired quality of life. While the findings of our study need to be confirmed in prospective studies, we have highlighted the potential role of psychological symptoms in determining quality of life in individuals with psoriasis. Future studies should also explore potential strategies to reduce the psychological impact of psoriasis to improve quality of life in these patients.