PORTLAND, Ore. (KOIN) — People with a statistically rare disease are at greater risk of depression and anxiety than people with more common diseases, according to a new study from Oregon State University.

Researchers have found that the millions of Americans collectively living with rare diseases have a lot in common when it comes to mental health issues. Participants in the study with “early onset with very severe symptoms” and “severe symptoms” showed the highest rates of psychological distress, regardless of the specific disease.

Several factors contribute to the psychological distress of a rare disease, including the time it takes to get diagnosed. In a previous study, OSU researcher Kathleen Bogart found that it takes an average of 10 years for rare diseases to be correctly identified, often because general practitioners have not been trained to recognize the symptoms and there are so few specialists focused on the disease.

Another study Bogart points to is one that looks at the physical impact of having a rare disease. People with rare diseases tend to experience substantially worse pain, fatigue and physical function than people with more prevalent chronic disorders like type 2 diabetes or stroke, according to Bogart.

“The main takeaway is that it’s useful to look at rare diseases collectively, instead of individually,” Bogart said. “When you look collectively, you can find broad groups that predict whether people will have psychological distress or not.”

The study, published in the journal Health Psychology, surveyed 1,218 adults with rare diseases and grouped participants based on age of onset, disease progression, visibility and symptom severity. The survey asked participants how their disease affects their daily life, including physical pain and fatigue as well as depression and anxiety.

A “rare disease” was defined in the study as being a disease that affects fewer than 200,000 people per year.