For some of us the trouble starts before we even step into a restaurant. If Carole Johnson, a retired school administrator in California, happens to have a distressing thought while passing through a doorway, she needs to “clear” the thought by passing through the door twice more.

My own challenge is fighting the urge to return to my parked car and check yet again that the parking brake is secure. If I don’t, how can I be sure my car won’t roll into something -- or worse, someone?

Johnson and I are among the millions battling obsessive-compulsive disorder, an anxiety disorder characterised by intrusive distressing thoughts and repetitive rituals aimed at dislodging those thoughts. We are an eclectic bunch spanning every imaginable cross-section of society and we battle an equally eclectic mix of obsessions and compulsions. Some of us obsess about contamination, others about hurting people, and still others about symmetry. Almost all of us can find something to obsess about at a restaurant.

Many of the situations that unsettle people with obsessive-compulsive disorder -- driving, for instance -- provoke at least some level of anxiety in just about everyone.

But restaurants are designed to be calming and relaxing. But we walk into a calm and civilised dining room and see things we won’t be able to control. This feeds directly into one of the unifying themes of the disorder: an often-crushing inability to handle the unknown.

“The common thread, I think, has something to do with certainty,” said Dr Michael Jenike, medical director of the Obsessive Compulsive Disorders Institute at McLean Hospital in Belmont, Massachussets, affiliated with Harvard Medical School.

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