Hand washing is a common OCD symptom. (Image credit: Digital Vision/Getty Images)

Imagine if a thought got stuck in your mind and played over and over again, eventually causing so much anxiety that you felt an overwhelming urge to repeat certain rituals or behaviors to cope with it.

That's what it's like for about 1 in 100 adults - between 2 and 3 million Americans - who suffer from obsessive compulsive disorder, or OCD.

The repetitive thoughts are known as obsessions and the rituals are known as compulsions. They can take over a person's life, ruling every waking moment and stealing valuable time and energy away from vital activities.

To better understand this puzzling condition, Dr. Richard Besser, ABC New's chief health and medical correspondent, held a tweet chat on Twitter earlier today. Mental health experts from the from the Mayo Clinic, the National Institute of Mental Health and the International OCD Foundation as well as scores of OCD therapists and sufferers, weighed in with their thoughts.

Here are five surprising facts about OCD that came out of the chat.

Fact 1: OCD starts young

For many, OCD develops early. Dr. Jeff Szymanski, executive director of the International OCD Foundation (IOCDF), said there are two peaks of onset: one at puberty, between the ages of 8 and 12, and one in late adolescence, between the ages of 18 and 22. Boys are more likely to be affected at an earlier age than girls.

Chelsea Ale, who specializes in treating pediatric anxiety disorders at the Mayo Clinic in Rochester, Minn., said that the onset may actually be even earlier - at the age of four or five - but may go unrecognized for many years.

"When people are diagnosed as adults, they usually report having had it since childhood," she said.

Fact 2: There may be a genetic component

Although the exact cause of OCD isn't well understood, scientists do suspect there is a strong genetic component. OCD can run in families. It's common among first degree relatives and even identical twins. Szymanski provided this link to the first-ever study to look which of the approximately 22,000 human genes may predispose individuals to OCD.

Fact 3: There may be a link between strep throat and OCD

Kids who contract strep throat can develop PANDAS - pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection. One of the symptoms is OCD. For years, medical experts thought the link between a strep throat and OCD was only coincidental, but now many believe PANDAS affect the part of the brain that controls movement and behavior.

Severe OCD symptoms appear suddenly with PANDAS - in some cases literally overnight - and can transform a happy outgoing child into a withdrawn, inconsolably anxious child in a matter of days. Current studies are investigating treating this type of OCD with antibiotics, in addition to traditional OCD therapies.

Christopher Sarampote, the chief of the prevention and treatment trials at the National Institute of Mental Health, said that the disorder has been recognized by the institute and research there is ongoing.

Fact 4: Good intentions can backfire

If a family member has OCD, you have surely asked, "What can I do to help?" But, while the support of loved ones can be essential to recovery, family involvement can backfire if understanding and accommodations lead to enabling.

"Trying to help avoid anxiety-provoking situations makes the world smaller and smaller and keeps OCD cycle going," Ale cautioned.

The best way to help a family member with OCD is to get educated. Szymanski offered this IOCDF resource.

Fact 5: You can conquer OCD

"Some estimates show that it takes 14-17 years between onset of OCD symptoms and getting effective treatment," Szymanski tweeted. "One estimate is that as many as 40 percent of individuals with OCD have never receive any treatment at all."

Sarampote added, "Delay in diagnosis may occur due to shame and feelings of distress. Many suffer in silence."

However, OCD doesn't have to be a lifetime sentence. There are effective therapies. Szyamanski said exposure and response prevention - ERP - is the gold standard for treatment. This involves gradually building up a tolerance to anxiety-producing circumstances. Research shows it can reduce symptoms by as much as 80 percent.

Ale said people who suffer from OCD may also find clinical behavioral therapy and medications such as selective serotonin reuptake inhibitors (SSRIs) useful.

"Seeking help for OCD was smartest decision I made. OCD can be defeated. I'm living proof," one participant tweeted.

Click here for a full transcript of the chat.

Dr. Besser Tweet Chats on Tuesdays from 1 to 2 p.m. ET

To raise public awareness about important health and medical topics, Besser hosts a one hour "tweet chat" most Tuesdays from 1 to 2 p.m. ET. His next chat on W omen's Heart Health takes place on Tuesday, Feb. 12. Want to participate? Here's how.