Psoriasis and Depression: Does One Cause the Other?
When it comes to psoriasis and depression, there’s no shortage of first-person stories of having both. Sam R., from Spokane, Washington, was first diagnosed with depression two years after his first psoriasis flare. But for Noemi L., from Evansville, Indiana, depression came first. It’s clear that many people experience both depression—and other mood disorders, like anxiety—and psoriasis. But what’s not so clear is whether one causes the other.
Is It the Stigma?
A population-based cohort study published in Archives of Dermatology found that people with psoriasis have a 39 percent increased risk of being diagnosed with depression compared to those without the disease. One theory is that the stigma and discrimination that often accompany a visible skin disease may increase the likelihood of depression. Sam can attest to this. “I noticed that my mood was lowest whenever I had a flare-up,” he says. “When the itch is bad, it’s uncomfortable to do the things I enjoy, like running and swimming. And I don’t want to get intimate with my girlfriend during a bad flare-up, which affects my self-esteem and my mental health in general.”
When Depression Comes First
Noemi’s experience of living with both psoriasis and depression is quite different. “I was diagnosed with depression at age 19,” she says. “In my mid 20s, I developed psoriasis.”
Is it possible that Noemi’s depression led to her psoriasis? Perhaps, but there’s no strong science to back that theory up. “Most of the literature has been focused on identifying association without causation, which means it shows that the two conditions are linked, but doesn’t demonstrate which comes first,” says Evan Rieder, M.D., a board-certified dermatologist and psychiatrist at NYU Langone Health in New York City.
The Role of Inflammation
Growing evidence suggests that inflammation could be an instrumental part of the link between psoriasis and mood disorders like depression. In one review, published in the Journal of the European Academy of Dermatology and Venereology, researchers suggested that systemic inflammation causes physiologic and biochemical changes that underlie depression.
Specifically, they found an elevation in cytokines (proteins that are involved in the inflammatory process of the immune system) in people with depression. This elevation has also been observed in people with psoriasis. Scientists believe that these inflammatory cytokines cross the blood-brain barrier and interfere with neurotransmitters like serotonin and dopamine, chemicals that play a big part in how we think, feel, and function.
“Psoriasis and depression share elevated levels of the same inflammatory mediators, indicating the possibility of common pathways between the two conditions,” explains Alia Ahmed, M.D., a psycho-dermatologist practicing in London, England.
But while this may show an association, it’s not the same thing as causation. “There is a well-established association between psoriasis and depression but we cannot say that psoriasis causes depression, or vice versa,” Rieder says. He points out that there are multiple factors that may contribute to the genesis of depression, such as genetics, stressful or traumatic life events and faulty mood regulation by the brain. And while someone may have depression and later develop psoriasis, that doesn’t mean the two are connected.
A Theory That Psoriasis Triggers Depression
Although Rieder can’t say with certainty that psoriasis could be a trigger for depression in people who have a history of mental illness, he does believe this is possible. Additionally, he says there is some suggestion that psoriasis in and of itself may cause some people who don’t have any such history of mental illness to develop mood or anxiety issues. Sam believes he falls into this category. “I had no experience of depression or any other mental health issue before I had psoriasis,” he says.
Ahmed says she has treated people with psoriasis who fall into both categories—those who have developed depression after being diagnosed with psoriasis, and those who developed depression first.
“At the time of diagnosis, people with psoriasis have shown to have higher prevalence of alcohol misuse, bipolar disorder, depression, anxiety disorders, and self-harm, and are more likely to be taking psychotropic medication,” she says. “At the same time, having a diagnosis of psoriasis increases a person’s risk for the development of depression, anxiety, and suicidality. More severe disease may result in a higher risk of developing depression, especially in young and male patients.”
It’s clear that further research is needed to figure out the exact mechanisms linking psoriasis and depression. “Determining which came first may be a chicken and egg situation,” Ahmed says.
In the meantime, people with both psoriasis and depression have not one but two serious illnesses with which to contend. It’s important that you have a stable treatment plan in place for both of them. If you feel that you need help managing your depression or your psoriasis (or both), reach out to your primary care doctor, dermatologist, or mental health profession. Ahmed says it’s also important to pay close attention to your diet, exercise, and sleep habits. Aim for a balanced diet with a good mix of fresh fruits and vegetables, at least two liters of water per day, regular exercise, and at least eight hours of sleep per night.
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