More evidence links psoriasis to depression

Roger S. Ho, MDA recent study provides more evidence that patients with psoriasis–even mild cases–face a higher risk of major depression, a finding that could lead dermatologists to alert patients with the condition and even screen them for mental health issues.

It's not clear how psoriasis and depression are linked. Still, "psoriasis patients should be counseled that psoriasis, a treatable disease, may place them at an elevated risk of depression," says study co-author Roger S. Ho, MD, MS, MPH, an assistant Professor of Dermatology with the New York University School of Medicine/Langone Medical Center. "However, many patients may not be cognizant of their own depression symptoms. As a result, dermatologists should be aware that all patients with psoriasis may benefit from depression screening."

Psoriasis isn't the only skin condition to be linked to mental illness. "There is an emerging literature on the association of skin diseases and depression," said Madhulika A. Gupta, MD, professor with the Department of Psychiatry at the University of Western Ontario. According to Dr. Gupta, studies typically link depression to the effect of the diseases on quality of life. But psoriasis is unusual among diseases linked to depression because it's been linked to especially high levels of psychiatric problems, including suicidal thoughts, he said.

In the recent study, which appears in the January 2016 issue of JAMA Dermatology, Dr. Ho and colleagues examine the results of questionnaires given to 12,382 people as part of the U.S. National Health and Nutrition Examination Survey between 2009 and 2012. They focused on 351 people with psoriasis (2.8%) and 968 who showed signs of major depression (16.5%).

The researchers found that 58 of the psoriasis patients -- 16.5% -- met criteria for major depression. After researchers controlled for various factors, patients with psoriasis had twice the odds (OR, 2.09 [95% CI, 1.41-3.11], P<.001) of major depression.

A history of heart attack and stroke didn't appear to boost the risk of major depression in patients with psoriasis. The researchers also found no significant connection between the severity of psoriasis and the risk of major depression.

It's not known if psoriasis causes or worsens depression–or vice versa–or if other factors may explain the apparent link. It's possible that "some unifying factors or mechanisms common to both psoriasis and depression might predispose a patient to both psoriasis and major depression," says study co-author Dr. Ho. "Or psoriasis or major depression might set off a cascade of events that make a patient more vulnerable to the other entity."

In regard to a specific mechanism, Dr. Gupta speculated that psoriasis and depression may affect each other, possibly when stressful life events disrupt the body's autonomic and immune responses. Dr. Gupta says this theory is supported by the fact that psoriasis patients face a higher risk of immune disorders–like diabetes and inflammatory bowel disease–and conditions related to the autonomic system like heart disease.

What should dermatologists do to help psoriasis patients?

Dr. Ho suggests that that they screen patients via the PHQ-2 questionnaire, which consists of "just 2 questions asking how often the patient has been bothered by any of the following problems over the past 2 weeks: 1. Little interest or pleasure in doing things; 2. Feeling down, depressed or hopeless."

The test is considered to be "positive" if patients answer yes to either question, regardless of how often they've been bothered by the symptoms. In that case, Dr. Ho says, dermatologists should talk to the patient about depression and encourage follow-up with a primary care provider or provide a referral to a psychiatrist.

For his part, Dr. Gupta says dermatologists should screen for depression and conditions like post-traumatic stress disorder that are more common in psoriasis patients. He suggests watching for these warning signs:

• Poor adherence to treatment regimens due to lack of motivation or cognitive difficulties

• An impact of psoriasis upon the quality of life that appears to be grossly out of proportion to disease severity or cosmetic disfigurement

• Resistance to standard therapies for psoriasis

• Frequent unexplained recurrence of psoriasis

• Suspicion of self-injury

• Overt psychiatric symptoms such as easy crying and thoughts about suicide

Dermatologists should consider seeking a psychiatric consultation if these warning signs appear in a patient, Dr. Gupta says, and find help immediately if a patient is at risk of suicide or self-injury.

What's next for research?

Dr. Ho says his team is looking for funding to support longitudinal clinical studies and basic science research to better understand the link between psoriasis and depression.