Intrusive thoughts can occur in the head at any time without any warning. Sometimes they seem quite rational - like worrying about whether you have turned off your iron or if you have contracted something by touching a dirty object. And sometimes - close to absurdity, such as the idea that the well-being of your loved ones depends on whether you lay out objects on the table or repeat an action a certain number of times. All this can create first inconvenience, and then serious problems in life.