Scaly, red skin – the symptoms of psoriasis – leave patients more vulnerable to depression, two large-scale studies from Denmark and South Korea confirm.
The Danish study, published in JAMA Dermatology, tracked around 13,700 patients with psoriasis between 1977 and 2013.
These patients were 75% more likely to develop a mental health condition than the general population, and 72% more likely to have depression.
Around 5% of the cohort had a mental disorder within 10 years of receiving a psoriasis diagnosis.
In the South Korean study with around 12,800 participants, psoriasis patients were more than twice as likely to have depression than the general population.
Patients with psoriasis were also at greater risk of anxiety disorders, sleep disorders, bipolar disorder, schizophrenia and vascular dementia.
Mental health disorder onset usually occurred within two or three months of psoriasis diagnosis, according to the South Korean data.
“Psoriasis can have a significant impact on the psychological health of patients because it is such a visual illness,” said Associate Professor Saxon Smith, a dermatologist at The University of Sydney.
“The general public, not recognising this as a genetically predisposed skin condition, assume it might be contagious, which it isn’t, and shun or shy away from people if they can see it on their skin.
“This often means sufferers cover up as best they can and won’t do every day activities like swimming.
“It can be very itchy but not always, which in turn can adversely affect people’s sleep. Sleep deprivation has a strong relationship with psychological impacts such as depression, anxiety and suicide.
“The condition tends to be very flakey, especially during flares. This leads to a patient shedding large amounts of skin all the time. Patients are very conscious of this and avoid wearing black, sitting on black chairs, and I have even had patients who have taken portable dust-buster vacuum cleaners away on holidays with them to vacuum up the scale they might leave behind.
“With all of these and other issues it is not surprising that there have been a long documented strong association between mental health issues and psoriasis.”
There could be another explanation too, however.
Emerging research suggested that the psoriasis inflammatory marker interleukin 17 could be linked to anxiety or depression, said Associate Professor Smith
“The mechanism underlying the development of mental disorders among those with psoriasis is not well understood,” the author of the accompanying editorial in JAMA Dermatology wrote.
“However, evidence suggests that enhanced activities in the Th17 pathway may play a role. For example, the level of interleukin 17 was significantly higher in activated T cells among those with anxiety or depression compared with controls.
“Thus, T cell functional dysregulation may contribute, at least in part, to the higher risk of mental disorders in patients with psoriasis.”
JAMA Dermatology 2019, May 8