The exact cause of psoriasis is unknown; however, scientists do believe that both genetics and environmental factors influence the onset and how the disease develops.
Genetic Risk Factors
As many as 7.5 million Americans have psoriasis and at least one third of those have at least one relative who also has psoriasis, although this estimate is considered low by some experts. In addition, if one parent has psoriasis, each child will have a 10 percent chance of developing psoriasis, if both parents have psoriasis, the percentage jumps up to 50 percent.
Identical twins have a 67 percent chance of both developing the disease.
Besides family history, your genes can play a role in whether you are at risk of developing psoriasis:
- Light-skinned individuals are more likely to develop psoriasis than dark-skinned people although African-Americans who live in colder climates develop psoriasis more often than those who live in warmer climates, such as Africa.
- Males are more at risk of developing psoriasis than women
Environmental Risk Factors
There are a number of environmental factors that are thought to be contributing factors to developing psoriasis:
Viral and Bacterial Infections - Individuals with HIV are more likely to develop psoriasis than those in the general public. In addition, psoriasis can flare up after upper respiratory conditions, such as tonsillitis, sinusitis and strep throat.
Injuries - Sometimes psoriasis will develop at the site of a previous skin injury, for example: cuts, burns or abrasions. This can occur with mild injuries as well as serious injuries.
Obesity - Individuals who are overweight are more likely to develop psoriasis than those who are not. One complication of psoriasis in those who are obese is that the plaques can develop within the folds and creases of the skin.
Smoking - Smoking has been associated with a higher risk of developing psoriasis. Additionally, there may be a link between the severity of the disease and smoking tobacco products.
Stress - Psoriasis is an autoimmune disease and stress can impact whether your immune system works properly. Because of this stress can influence the onset and the course of the illness. Stress is often thought of as a trigger for psoriasis flare ups.
Medications - Certain medications, such as antibiotics, are often thought of as a risk factor for developing psoriasis, however, a study reported in Arch Dermatology in 2007 indicated that it is possible the underlying infection is the cause of the psoriasis rather than the medication. Other medications which are associated with psoriasis are beta blockers, used to treat high blood pressure, lithium, used to treat mood disorder and antimalarials which are sometimes used to treat arthritis or lupus.
Although lifestyle factors may not impact whether or not you develop psoriasis, they may impact the severity of the disease and trigger flare-ups.
Changes in your lifestyle, such as quitting smoking, losing weight, eating healthy, avoiding alcohol may help to reduce the severity and number of flare-ups. In addition, cold weather can worsen psoriasis. Warm, humid climates help to reduce the outbreaks of psoriasis.
"Incidence and Risk Factors for Psoriasis in the General Population, 2007, Consuelo Huerta, Elena Rivero, Luis A. Garcia Rodrigues, Arch Dermatology, Vol. 143
"Psoriasis - Causes," Reviewed 2009, April 10, Reviewed by David Zieve, Greg Juhn and David R. Eltz, University of Maryland Medical Center, A.D.A.M. Medical Encyclopedia