When most people think of obsessive-compulsive disorder, they may picture behaviors they’ve seen on TV — like repetitive hand-washing, flicking light switches on and off and meticulously arranging small items over and over.

But the disorder manifests in many other ways. Some patients obsess over thoughts that they might hurt someone, while others fixate on certain aspects of their personal relationships.

The comedian Maria Bamford, for example, has called her O.C.D. “unwanted thoughts syndrome.” On “The Late Show With Stephen Colbert,” she shared a story about how she couldn’t stop thinking horrific thoughts about her family members.

On social media, people describe many types of obsessions and compulsions: “relationship O.C.D.,” “sexual orientation O.C.D.” or “emotional contamination O.C.D.” These aren’t separate diagnoses, but rather they are different expressions of the same disorder — much like how people with phobias can suffer from different fears, said Dr. Carolyn Rodriguez, an O.C.D. expert and a professor of psychiatry and behavioral sciences at Stanford Medicine.

Understanding these distinctions can help clinicians tailor a precise treatment plan, she added. And they’re important for the public to grasp as well. Otherwise, people who experience the disorder might not even recognize they have it, Dr. Rodriguez said.

People who are fearful of harming others might think, “Maybe I am a murderer,” she added. “If I tell anybody these things, I’m going to be put in jail.”

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