Abstract
This study examines the association between psoriasis and subsequent development of mental disorder using data on individuals with at least 2 hospital- or outpatient-based diagnoses of psoriasis from population-based registries covering all Danish hospitals.
Psoriasis has been reported to be associated with an elevated risk of various mental disorders, including depression, anxiety, and suicidality.1 However, to our knowledge, no studies have determined the long-term risk of a broader spectrum of adult-onset mental disorders in a large cohort of individuals with psoriasis. Given the high prevalence of psoriasis—between 2% and 4% in adults2—investigation of the association of this condition with mental health has important public health implications. Therefore, we aimed to elucidate the association between psoriasis and the entire spectrum of adult-onset psychiatric morbidity. The study was approved by the Danish Data Protection Agency, whose role is to protect the privacy of individuals whose data are recorded in Danish registries. No informed consent was required for this study.
Methods
We used data from population-based registries covering all Danish hospitals to identify individuals born from 1900 to 1995 who had at least 2 hospital- or outpatient-based diagnoses of psoriasis from January 1, 1977, to January 1, 2012. Using the Danish Civil Registration System, we identified 10 population-comparison cohort members matched on sex and birth year. Follow-up was continued until diagnosis of a mental disorder, death, emigration, or end of the study (January 1, 2013). Only diagnoses of mental disorders made at either inpatient or outpatient facilities were considered (as registered in the Danish Central Psychiatric Research Register). Data analysis was performed from January 1 to March 1, 2017.
To test the association between psoriasis and subsequent development of mental disorder, we computed cumulative incidences accounting for death as a competing risk, incidence rates, and calculated hazard ratios (HRs) of time to diagnosis of any mental disorder, as well as specific mental disorders, adjusting for birth year and sex. We also performed subgroup analyses according to educational level (short-term, medium-term, long-term) of patients with psoriasis. Furthermore, comorbidities were identified to evaluate the association of these conditions with the development of mental disorders among individuals with psoriasis. Statistical analysis was performed with Stata, version 14 (StataCorp).
Results
We identified 13 675 individuals with psoriasis (50% male) (Table 1). The 5- and 10-year cumulative incidences of any mental disorder were 2.6% and 4.9%, respectively. The HR of any mental disorder was 1.75 (95% CI, 1.62-1.89) when comparing those with psoriasis with the general population cohort (Table 2). The HRs for selected mental disorders were as follows: 1.73 (95% CI, 1.21-2.47) for vascular dementia, 1.64 (95% CI, 1.01-2.65) for schizophrenia, 2.33 (95% CI, 1.59-3.41) for bipolar disorder, 1.72 (95% CI, 1.49-1.98) for unipolar depression, 1.88 (95% CI, 1.08-3.30) for generalized anxiety disorder, and 2.06 (95% CI, 1.55-2.73) for personality disorders. The risk of mental disorders among individuals with psoriasis who had completed short-term education presented with an HR of 2.18 (95% CI, 1.95-2.44), while those who had attained medium- and long-term educational levels demonstrated HRs of 1.45 (95% CI, 1.26-1.67) and 1.40 (95% CI, 1.11-1.78), respectively.
Table 1. Characteristics of the Psoriasis Cohort and the General Population Comparison Cohort.
| Variable | Cohort, No. (%) | |
|---|---|---|
| Psoriasis | General Population | |
| All | 13 675 | 141 040 |
| Male | 6891 (50.4) | 71 172 (50.5) |
| Birth year | ||
| 1900-1919 | 1477 (10.8) | 14 016 (9.9) |
| 1920-1939 | 3276 (24.0) | 33 765 (23.9) |
| 1940-1959 | 4992 (36.5) | 52 699 (37.4) |
| 1960-1979 | 3074 (22.5) | 31 727 (22) |
| 1980-1995 | 856 (6.3) | 8833 (6.3) |
| Age at first psoriasis diagnosis, y | ||
| 0-19 | 638 (4.7) | NA |
| 20-39 | 3055 (22.3) | NA |
| 40-59 | 5105 (37.3) | NA |
| 60-79 | 4207 (30.8) | NA |
| ≥80 | 670 (5.0) | NA |
| Educational level attainmenta | ||
| Short-term | 5218 (38.2) | 48 531 (34.4) |
| Medium-term | 4799 (35.1) | 51 461 (36.5) |
| Long-term | 1873 (13.7) | 24 659 (17.5) |
| Missing | 1785 (13.1) | 16 389 (11.6) |
| Comorbidities | ||
| Diabetes | 929 (6.8) | 3416 (2.4) |
| Stroke | 403 (2.9) | 2011 (1.4) |
| Acute myocardial infarction | 433 (3.2) | 2697 (1.9) |
Abbreviation: NA, not available.
Short-term: completion of primary education (7-10 years), medium-term: vocational training (3- to 4-year programs completed after primary education) or high school (3-year secondary education, known as gymnasium), long-term: university education at bachelor or master degree level.
Table 2. Incidence Rates and HRs of Mental Disorders Among Individuals With Psoriasis Compared With the General Population Cohort.
| Variable | ICD-10; ICD-8 Codes | IR (95% CI) | HR (95% CI) | |||||
|---|---|---|---|---|---|---|---|---|
| No. of Cases | Incidence per 1000 Person-Years (95% CI) | Overalla | Male | Female | ||||
| Psoriasis Cohort | Comparison Cohort | Psoriasis Cohort | Comparison Cohort | |||||
| Any mental disorder | F00-F99; 290-315 | 801 | 6140 | 6.56 (6.12-7.03) | 4.08 (3.98-4.18) | 1.75 (1.62-1.89) | 1.98 (1.77-2.22) | 1.58 (1.42-1.76) |
| Organic, including symptomatic mental disorders | F00-F09; 290.09, 290.10, 290.11, 290.18, 290.19, 292.x9, 293.x9, 294.x9, 309.x9 | 193 | 2278 | 1.53 (1.32-1.76) | 1.49 (1.43-1.55) | 1.40 (1.20-1.64) | 1.72 (1.37-2.16) | 1.19 (0.95-1.48) |
| Dementia in Alzheimer disease | F00; 290.09, 290.10, 290.19 | 63 | 939 | 0.50 (0.39-0.63) | 0.61 (0.57-0.65) | 1.14 (0.87-1.50) | 1.26 (0.82-1.92) | 1.08 (0.76-1.53) |
| Vascular dementia | F01; 293.09, 293.19 | 39 | 442 | 0.31 (0.22-0.42) | 0.29 (0.26-0.32) | 1.73 (1.21-2.47) | 2.72 (1.70-4.35) | 1.03 (0.58-1.84) |
| Mental and behavioral disorders due to psychoactive substance abuse | F10-F19; 291.x9, 294.39, 303.x9, 303.20, 303.28, 303.90, 304.x9 | 140 | 611 | 1.11 (0.94-1.31) | 0.40 (0.37-0.43) | 2.75 (2.27-3.33) | 3.05 (2.43-3.83) | 2.19 (1.54-3.12) |
| Alcohol use | F10; 291.x9, 303.x9, 303.20, 303.28, 303.90 | 118 | 493 | 0.93 (0.78-1.12) | 0.32 (0.29-0.35) | 2.93 (2.37-3.61) | 3.31 (2.58-4.23) | 2.19 (1.47-3.28) |
| Cannabis use | F12; 304.59 | 5 | 42 | 0.039 (0.016-0.094) | 0.027 (0.020-0.037) | 1.18 (0.46-3.01) | 1.03 (0.31-3.40) | 1.53 (0.34-6.94) |
| Schizophrenia and related disorders | F20-F29; 295.x9, 296.89, 297.x9, 298.29-298.99, 299.04, 299.05, 299.09, 301.83 | 68 | 451 | 0.54 (0.42-0.68) | 0.29 (0.27-0.32) | 1.82 (1.40-2.37) | 2.24 (1.57-3.20) | 1.45 (0.98-2.16) |
| Schizophrenia | F20; 295.x9 (excluding 295.79) | 20 | 122 | 0.16 (0.10-0.24) | 0.079 (0.066-0.095) | 1.64 (1.01-2.65) | 1.55 (0.81-2.96) | 1.76 (0.85-3.62) |
| Mood disorders | F30-F39; 296.x9 (excluding 296.89), 298.09, 298.19, 300.49, 301.19 | 261 | 1826 | 2.08 (1.84-2.34) | 1.20 (1.14-1.25) | 1.79 (1.56-2.04) | 1.95 (1.57-2.41) | 1.69 (1.42-2.01) |
| Bipolar disorders | F30-F31; 296.19, 296.39, 298.19 | 34 | 181 | 0.27 (0.19-0.37) | 0.12 (0.10-0.14) | 2.33 (1.59-3.41) | 2.07 (1.12-3.80) | 2.52 (1.55-4.11) |
| Unipolar depression | F32-F33; 296.09, 296.29, 298.09, 300.49 | 227 | 1658 | 1.80 (1.58-2.05) | 1.08 (1.03-1.14) | 1.72 (1.49-1.98) | 1.87 (1.49-2.36) | 1.63 (1.35-1.96) |
| Neurotic, stress-related, and somatoform disorders | F40-F48; 300.x9 (excluding 300.49), 305.x9, 305.68, 307.99 | 238 | 1462 | 1.89 (1.67-2.15) | 0.96 (0.91-1.01) | 1.83 (1.59-2.10) | 1.93 (1.55-2.40) | 1.76 (1.47-2.12) |
| Obsessive-compulsive disorder | F42; 300.39 | 5 | 48 | 0.039 (0.016-0.094) | 0.031 (0.024-0.041) | 1.14 (0.45-2.90) | 1.84 (0.52-6.50) | 0.73 (0.17-3.08) |
| Phobic anxiety disorders | F40; 300.29 | 13 | 86 | 0.10 (0.059-0.18) | 0.056 (0.045-0.069) | 1.67 (0.92-3.04) | 1.98 (0.81-4.85) | 1.48 (0.66-3.30) |
| Panic disorder | F41.0; NA | 8 | 62 | 0.063 (0.031-0.13) | 0.040 (0.031-0.052) | 1.32 (0.62-2.78) | 1.24 (0.36-4.19) | 1.37 (0.53-3.53) |
| Generalized anxiety disorder | F41.1; 300.09 | 15 | 91 | 0.12 (0.071-0.20) | 0.059 (0.048-0.073) | 1.88 (1.08-3.30) | 0.88 (0.20-3.78) | 2.29 (1.24-4.22) |
| Trauma- and stressor-related disorders | F43; 307.99 | 178 | 1042 | 1.41 (1.22-1.64) | 0.68 (0.64-0.72) | 1.92 (1.63-2.26) | 1.98 (1.54-2.55) | 1.88 (1.52-2.33) |
| Eating disorders | F50; 306.50, 306.58, 306.59 | 7 | 66 | 0.055 (0.026-0.115) | 0.043 (0.034-0.055) | 1.14 (0.52-2.52) | NA | 1.16 (0.53-2.56) |
| Anorexia nervosa | F50.0; 306.50 | 4 | 23 | 0.031 (0.012-0.084) | 0.015 (0.0099-0.022) | 1.93 (0.65-5.71) | NA | 2.03 (0.68-6.04) |
| Specific personality disorders | F60; 301.x9 (excluding 301.19), 301.80, 301.81, 301.82, 301.84 | 60 | 331 | 0.47 (0.37-0.61) | 0.22 (0.19-0.24) | 2.06 (1.55-2.73) | 1.64 (0.99-2.72) | 2.30 (1.64-3.24) |
| Borderline type | F60.31; 301.84 | 8 | 0.063 (0.031-0.126) | 0.038 (0.029-0.050) | 1.39 (0.66-2.94) | NA | 1.85 (0.86-4.00) | |
Abbreviations: HR, hazard ratio; ICD-8, International Classification of Diseases, Eighth Revision; ICD-10, International Statistical Classification of Diseases and Related Health Problems, Tenth Revision; IR, incidence rate; NA, not applicable.
Adjusted for birth year and sex.
Discussion
Our findings are in agreement with those of previous research, indicating a higher risk of depression among individuals with psoriasis.1 Furthermore, our findings suggest a higher risk of bipolar disorder among those with psoriasis than among matched controls. To our knowledge, no studies have evaluated bipolar disorder in the context of psoriatic pathogenesis; however, a heightened risk of bipolar disorder among individuals with psoriasis is in line with hypotheses suggesting an inflammation-mediated induction and/or progression of bipolar disorder.3 Similarly, immune dysregulation has been suggested to play a pivotal role in schizophrenia.4 We also found an increased risk of vascular dementia among individuals with psoriasis. It has been reported that the prevalence of mild cognitive impairment is higher among individuals with psoriasis5 and that the risk of death due to dementia may be elevated among individuals with psoriasis.6 However, to our knowledge, no previous, larger studies have determined the risk of dementia within this patient population. The findings reported herein support the need for an approach when treating individuals with psoriasis that focuses not only on their dermatologic condition, but also on their mental health.
References
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