Is a 'Shadow Disease' Lurking in Your Body?

Doctors are aware that patients who have one illness may tend to develop another problem that appears to be unrelated to the first. The second condition is often called a "shadow disease" and may actually be more serious than the disease already diagnosed.

Shadow illnesses can occur for different reasons. Some diseases cause damage that creates the second illness. In other cases, faulty genes or poor lifestyle choices combine to cause both conditions.

Here are seven common health conditions and their "shadows." If you have one of the conditions, being aware of its shadow can help you get early diagnosis and treatment.

1. Psoriasis and heart attack
Psoriasis can double the risk of having a heart attack, said Dr. David Ancona, FACC cardiologist at Memorial Hospital West in Pembroke Pines, Fla. "There are diseases that exist that., for some reason or another, seem to follow one another like a shadow," he told ABC news.

2. Metabolic syndrome and kidney stones
Having three of the five risk factors tied to metabolic syndrome, which are belly fat, high cholesterol, high blood pressure, high sugar levels, and elevated C-reactive protein in blood increases the risk of kidney stones by 70 percent.

3. High blood pressure and diabetes
Harvard researchers found that women who have blood pressure that is constantly elevated — even if it's not classified as "high" — double their risk of developing diabetes regardless of their body mass index. In addition, studies at Rush University found a link between medicines used to treat high blood pressure and the development of diabetes.

4. Depression and dementia
The Framingham Heart Study found that depression increases the risk for Alzheimer's and dementia in older people. The study, which followed patients for up to 17 years, discovered that those who suffered from depression at the beginning of the study had a 70 percent greater risk of developing dementia. Two additional new studies found a similar link. "The association between depression and dementia has been a major topic for more than two decades, and it is increasingly clear this association is real," Alzheimer's researcher Dr. Yonas E. Geda, an associate professor of neurology and psychiatry at the Mayo Clinic College of Medicine in Rochester, Minn., told WebMD.

5. Endometriosis and melanoma
French researchers found that women who have endometriosis have a 62 percent increased risk of developing melanoma. If you have endometriosis, be sure wear sunscreen and have your skin checked regularly for melanoma.

6. Migraine and heart attack or stroke
According to a recent study by researchers at Albert Einstein College of Medicine, those who have migraines are twice as likely to have heart attacks. "Our study suggests that migraine is not an isolated disorder and that, when caring for people with migraine, we should also be attentive to detecting and treating their cardiovascular risk factors," Dr. Richard B. Lipton, lead author of the study, said in a statement. For sufferers whose migraines are accompanied by auras, the risk tripled. Other studies found that migraines doubled the risk of stroke, but one migraine a week increased the risk of stroke fourfold.

7. Asthma, depression, and anxiety
People with asthma more than double their chances of suffering depression or anxiety. A King's College, London, study found that depression was significantly higher among people with asthma. Another study found that veterans with the worst cases of post-traumatic stress disorder doubled their risk of asthma when compared to those with the mildest cases.