Mandel talked publicly for the first time about his condition -- he also suffers from attention deficit disorder - on "The Howard Stern Show" in 2006. Mandel joked that his condition even prevented him from cheating on his wife for 20 years, because he was too afraid to make any moves on the models who appear on "Deal."
Obsession: His own fears
Stern has been outspoken about his own struggles with OCD. In his 1995 book "Miss America," he described how he could not turn on the car radio without tapping the dial a certain number of times with his right hand.
"The ... rituals were my distraction,'' he wrote. "When I was in college and nervous about entering the world of broadcasting and earning a living, the pressure was enormous. ... As a defense mechanism, my brain had set up an elaborate maze of rituals that kept me from confronting my fear."
He said once he made the connection, he instantly stopped his compulsive behavior and now practices transcendental meditation.
The basic treatment for OCD involves exposure to one's thoughts, then preventing the response or compulsive behavior. Whiteside said severe OCD sufferers will require the help of a therapist. Others can take a more mindfulness approach, like Stern, and simply allow their thoughts to surface and not react to it, he said.
The "Titanic" actor once played another famous sufferer of OCD, Howard Hughes. In fact, while playing the role, DiCaprio's got back in touch with his own childhood obsession: sidewalks.
"I remember as a child, stepping on cracks on the way to school and having to walk back a block and step on that same crack or that gum stain," DiCaprio told About.com at the time the Hughes biopic "The Aviator" was released.
"Let's just say it took me a while to get to set, having to step on tons of things," he said, laughing.
Diaz will open doors with her elbows just to avoid touching the germ-infested doorknobs.
The sexy star of "Shrek" and "Charlie's Angels" has admitted to cleaning the doorknobs of her Los Angeles home so much that the original paint has faded on them. She has also said she washes her hands "many times" each day.
But perhaps her obsession has diminished somewhat. In May 2007, she told a reporter, "I think I've made my peace with it."
Diaz's ex, Justin Timberlake, has also copped to having OCD. He was quoted by the Web site Collider.com as saying, "I have OCD mixed with ADD (attention deficit disorder). You try living with that. It's complicated."
Whiteside said OCD and ADD or ADHD (attention deficit hyperactivity disorder) often go together. He said OCD symptoms that present early in childhood, particularly for boys, are likely to be associated with ADHD and tics.
Beckham likes to keep his shirts in order, lining them up in the closet according to color. So do a lot of people, you say. How about matching all the food in your refrigerator? Apparently, the soccer star likes order in his fridge as well, which is why he has three.
"Food in one, salad in another and drinks in the third," his wife Victoria Beckham said, according to the Daily Mail. "In the drinks one, everything is symmetrical. If there's three cans of Diet Coke, he'd throw one away rather than having three -- because it has to be an even number."
"He's got that obsessive-compulsive thing where everything has to match," she said.