What is schizophrenia?
Schizophrenia is a neuropsychiatric condition characterised by psychotic symptoms including hallucinations, delusions, and disorganised speech/behaviour, as well as negative symptoms including diminished emotional expression and a loss of interest in activities. Schizophrenia affects approximately 1% of the world population, with a global point prevalence of 0.28%.
What is the link between stress, schizophrenia, and skin disease?
The relationship between stress and skin disease is bi-directional; stress can worsen skin diseases, and the skin disease can worsen stress. Chronic stress reduces activity of the hypothalamic-pituitary-adrenal (HPA) axis and upregulates sympathetic-adrenal-medullary responses; this stimulates pro-inflammatory cytokines which may contribute to inflammatory skin disorders and schizophrenia in patients with a pre-existing susceptibility. Patients with schizophrenia often experience high levels of psychosocial stress, perhaps making them more susceptible to skin diseases.
Pharmacological treatments for stress-related anxiety and schizophrenia also increase the risk of skin conditions as adverse effects.
What inflammatory skin diseases have been studied in association with schizophrenia?
Several population-based studies have identified an increased risk of psoriasis in individuals with schizophrenia compared to the general population. Cross-sectional studies have reported an increased prevalence of schizophrenia in patients with psoriasis compared to controls. Other studies have failed to support the association between schizophrenia and psoriasis. More evidence is needed to clarify the association.
As with psoriasis, there are conflicting study outcomes examining the association between atopic dermatitis and schizophrenia. One study reported that children with atopic dermatitis had an increased risk of having a psychotic episode by age 13 years. Another found that when schizophrenia was the primary reason for admission to hospital, it was more common in adults with co-morbid atopic dermatitis than those without atopic dermatitis. Other studies have not supported an association between the two conditions.
Hidradenitis suppurativa is associated with an increased risk of mental health disorders and an association with schizophrenia has been reported in both retrospective and cross-sectional studies.
Acne vulgaris and rosacea
A large cohort study reported an association between primary admission to hospital for schizophrenia and acne vulgaris. A cross-sectional study found a significantly higher prevalence of schizophrenia in patients with acne when compared to the global prevalence of schizophrenia. In contrast, patients with rosacea have been reported to have a decreased risk of schizophrenia.
Autoimmune blistering disorders
Studies examining the association between bullous pemphigoid and schizophrenia report conflicting results, with some finding an elevated risk of bullous pemphigoid in schizophrenia patients, and others failing to find an association between the two conditions.
One large population-based study reported a higher prevalence of schizophrenia in pemphigus patients when compared to age, sex, and ethnicity-matched controls. Two studies failed to find an association with pemphigus among individuals with a family history of schizophrenia.
Alopecia areata and vitiligo
It is unclear whether there is an association between alopecia areata, vitiligo, and schizophrenia, with conflicting study results; increased prevalence, reduced risk, and no association have all been reported.
Autoimmune connective tissue diseases
Conflicting results are reported linking schizophrenia with systemic lupus erythematosus, dermatomyositis, and scleroderma, with some finding a positive association and others failing to find any association.
A cohort study in Sweden found that patients with Darier disease had 2.3 times the risk of being diagnosed with schizophrenia compared to controls. Mutations in the ATP2A2 gene cause Darier disease and there is evidence these also increase the risk of psychiatric illness.
Single case reports link schizophrenia and other genodermatoses such as Hailey-Hailey disease, X-linked ichthyosis, dyskeratosis congenita, tuberous sclerosis, and Peutz-Jeghers syndrome, which may reflect the population incidence.
What are the adverse skin effects of psychotropic drugs?
Adverse cutaneous reactions to psychotropic drugs are common, and reported to affect 2–5% of patients taking them.
What can we conclude about the link between skin disease and schizophrenia?
Although there is strong evidence linking schizophrenia with a number of autoimmune conditions such as multiple sclerosis, inflammatory bowel disorders, and thyrotoxicosis, evidence linking schizophrenia to autoimmune skin diseases is inconsistent.
It has been postulated that because one of the disorders brings the individual under close medical monitoring, the second condition is more likely to be noted and documented. The role of treatment for one condition unmasking or triggering the other should also be considered.