May 26, 2010 (New Orleans) -- People with bipolar disorder are two to four times as likely as people without the disorder to suffer from various skin conditions, including psoriasis and eczema, researchers report.
They're also 2.6 times more likely to have hypothyroidism, 2.3 times more likely to have hay fever, 90% more likely to suffer from migraine headaches, 60% more likely to have viral hepatitis, 60% more likely to be obese, 40% more likely to have asthma, and 40% more likely to have epilepsy than other people, says Jared A. Fisher, MPH, of the Walter Reed Army Institute of Research in Silver Spring, Md.
"We think some of these conditions may be side effects of the drugs used to treat bipolar disorder," he tells WebMD. "For example, lithium can cause psoriasis, and some mood stabilizers have been linked to hypothyroidism."
Others may share a common causal factor with bipolar disorder, he says. For example, some research shows that bipolar disorder, increased body weight, and hypertension are all related to elevated norepinephrine levels.
"But with others, we just have no idea as to why [rates are higher in people with bipolar disorder].
"We're just trying to find the most common disorders in people with bipolar disease and set the stage for future research," Fisher says.
The findings were presented at the American Psychiatric Association meeting.
Previous research has shown that 40% to 56% of people with bipolar disorder have been diagnosed with one or more other medical conditions, Fisher says.
For the current study, the researchers used data from the 1979-2006 National Hospital Discharge Survey (NHDS) to compare rates of various diseases in 27,054 people with bipolar disorder and 2,325,247 people without the disorder.
The researchers say that one strength of the study is that it used a large, nationally representative database.
A weakness is that it relied solely on hospital discharge data, so a person who goes in and out of the hospital could be counted more than once.
Philip Muskin, MD, professor of clinical psychiatry at Columbia University in New York City, says that one reason people with bipolar disorder may be more likely to develop certain disorders is that "they don't always get good medical care because many don't like to go see doctors. A lot of times, when I say to patients, 'Let’s talk to your internist,' they reply that they don't have one. I consider it my job to help them find an internist."
Bipolar Disorder and High Blood Pressure
A second study presented at the meeting showed that nearly half of people with bipolar disorder suffer from high blood pressure, compared with about one-third of people in the general population.
Previous research has shown that people with bipolar disorder suffer a disproportionate burden of heart disease, metabolic syndrome, and stroke, says Dale D'Mello, MD, of Michigan State University.
To try to better understand the relationship, D'Mello and colleagues studied 99 people with bipolar disorder who were treated at St. Lawrence Hospital in Lansing, Mich., between 2002 and 2006.
A total of 45% had hypertension. In contrast, the government's Healthy People 2010 initiative put the rate of high blood pressure in the general population at 30.5%.
The average age of the bipolar patients with hypertension was 44, compared with 37 for those with normal blood pressure. They were also more likely to be obese, with an average body mass index of 33 vs. 28 for those with normal blood pressure.
Hypertensive patients also had higher average scores on a 56-point scale used to gauge mania -- 40 vs. 35 -- and they were diagnosed with bipolar disorder earlier, at an average age of 24, compared with 29 in patients with normal blood pressure.
The study had some major limitations, such as not taking into account the use of certain antipsychotic drugs that can lead to metabolic syndrome, D'Mello says.
Nevertheless, the link is worthy of further study, he tells WebMD. "It opens a host of questions. Do some patients become hypertensive because they have mania? Could keeping patients stable prevent hypertension? And could treating hypertension change the outcome of bipolar disorder? These are all issues to be explored."
Muskin says it's also possible that some of the drugs used to treat bipolar may be contributing to the higher rate of hypertension because they can cause weight gain. Obesity is a risk factor for high blood pressure.
This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.