Psoriasis & Comorbidities: Unraveling the Maze

Abstract

In this thesis we used a multifaceted approach to analyzing depression in psoriasis, by investigating Health Related Quality of Life (HRQoL), depressive symptoms, clinical depression and antidepressant use, using various data sources and statistical methods. These include a cross-sectional study, two population-based cohorts and a systematic review of the literature incorporated into a meta-analysis. A total of 40% of psoriasis patients from dermatological outpatient clinics in Belgium reported a substantial impact of psoriasis on their lives according to dermatology specific questionnaires. The level of generic impairment of the quality of life was comparable to the level observed in other chronic diseases such as asthma, diabetes and rheumatoid arthritis and also comparable to the level found in prostate cancer patients and patients with hematological malignancies. Patients with moderate to severe disease reported higher quality of life scores than those with milder disease, regardless of whether dermatology specific or generic instruments were used. According to a systematic review and meta-analysis of the literature on depression in psoriasis, one quarter of psoriasis patients manifest depressive symptoms and 12% are diagnosed with clinical depression. Psoriasis patients are one and a half times more likely to manifest signs of clinical depression compared with their healthy peers. Depressive symptoms in psoriasis were assessed in mostly small studies based in tertiary centers. The relationship between psoriasis and clinical depression was investigated in large population-based studies using administrative databases. The actual prevalence of depression according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) criteria is hard to estimate due to the scarcity of available studies. However it is definitely lower than the prevalence of depressive symptoms. This difference was also noted in the population-based Rotterdam Study, where we demonstrated that symptoms of depression assessed according to the Center for Epidemiologic Studies Depression Scale (CES-D) >16 were manifest in 8.5% of 236 psoriasis patients, however when the patients with an elevated CES-D score underwent clinical examination by the psychiatrist, only 3 patients were diagnosed with a major or minor depression according to the DSM-IV. According to the meta-analysis we conducted, the overall pooled antidepressant use in psoriasis in the literature was 9% (6-14%). Data on drug dispenses from the Dutch pharmacy database showed that psoriasis patients were one and a half times more likely to use an antidepressant compared to the reference group (after adjustment for age, gender and general healthcare consumption). The use of antidepressant medication peaked when patients sought medical care for their psoriasis and thereafter.
The effect of this increased healthcare seeking behavior was also reflected in the results from the Dutch General Practitioner (GP) database which show that psoriasis patients use significantly more medication of all therapeutic groups than patients without psoriasis of the same gender, age and GP practice. Patients with moderate to severe psoriasis had more prescriptions for medication compared to patients with mild disease. In the Dutch GP database the odds of antidepressant use was 1.35, 95%CI 1.26-1.45 in psoriasis patients compared to controls without psoriasis, which is in in the range of the results from the data we obtained from the Dutch pharmacy database (OR 1.47, 95% 1.43-1.51), with a dose-response for patients with moderate to severe disease in both studies.