MONDAY, Nov. 19 (HealthDay News) -- Children who have the skin condition psoriasis are about twice as likely to be either overweight or obese as kids without the skin problem, according to new research that looked at children from nine countries.

When researchers looked at just obesity, they found those with the skin condition were four times as likely to be obese, said Dr. Amy Paller, a professor and chair of dermatology at Northwestern University Feinberg School of Medicine, who led the study. It is published online Nov. 19 in the Archives of Dermatology.

U.S. children with severe psoriasis were seven times as likely to be obese as children without the skin condition.

"Pediatric psoriasis is a little bit of an orphan," Paller said. "It's very little studied."

She decided to take a closer look, especially because much research has shown that adults with psoriasis are often overweight. Experts have found a link, not cause and effect.

Psoriasis is marked by red, often itchy and scaly lesions. They can be confined to just some areas, such as the scalp and elbows, or cover much of the body.

The condition can make children self-conscious, affecting their social life and willingness to exercise, among other things, according to Paller.

She evaluated 614 children, ages 5 to 17. While 409 had psoriasis, 205 did not and served as the comparison group.

Of those with psoriasis, about half had mild forms and the other half severe.

About 30 percent of the children with psoriasis had an immediate family member with it. Experts know there is a strong genetic component to the condition.

The findings did not surprise Paller. "We found that, as we suspected, the body mass index of the overall group of kids with psoriasis was much higher,'' she said. Body mass index (BMI) is a measurement of body fat that takes height and weight into account.

Even the children with mild psoriasis were more likely to be overweight.

Which condition drives the other? "My speculation is that they are heavy and that psoriasis is part of the metabolic disease," she said.

Experts know that an overproduction in the body of substances called inflammatory cytokines is associated with both obesity and psoriasis in adults. So inflammation may drive both disorders, according to Paller.

When obese adults with psoriasis lose a lot of weight, their psoriasis may go into remission, studies suggest.

The new research findings suggest that dermatologists need to have a more ''holistic'' approach when treating kids with psoriasis, Paller said. "You can't just jump in and treat them with systemic medications or topical," she said. Doctors have to heed weight issues, she added.

In agreement is Dr. Ana M. Duarte, director of pediatric dermatology at Miami Children's Hospital. She reviewed the study findings.

"What I took away from this is, we need to get a handle on obesity in this country," Duarte said.

The research findings seem to reflect what she sees in her practice. "Thinking back, some of my obese patients have more severe disease," she said. "The milder are not as obese."

For parents, the best advice is to seek a doctor's care, said Dr. Lawrence Green, chair of the research committee for the National Psoriasis Foundation. "Whether your child is overweight, has psoriasis, or both, please seek help from your doctor (for weight advice) or your dermatologist for help in treating psoriasis because both conditions cause chronic inflammation in the body and this can lead to heart and other metabolic disease in their future," he said.

Another dermatologist discussed the study's implications.

"This paper highlights the clear association between obesity and psoriasis," said Dr. Michele Green, a dermatologist at Lenox Hill Hospital in New York City. While it is unclear which comes first, she said, "I suspect that the obesity leads to an increased risk for the development of psoriasis."

The study was funded by the International Psoriasis Council. Paller reported unpaid investigator work for some pharmaceutical companies and honoraria from Abbott, Amgen-Immunex, Johnson & Johnson, and Leo Pharma. Other study authors report research grants and consultant work for several pharmaceutical companies.

While the study found an association between child obesity and overweight and psoriasis, it did not prove a cause-and-effect relationship.

More information

To learn more about psoriasis, visit the U.S. National Institutes of Health.