This week I wanted to push people down the escalator at London Bridge station on more than one occasion. I also had strong images of punching a man in the face who kept pushing his backpack into my legs on the 06.54 train from East Dulwich. The trains can be grim when they are especially crowded, but I have never actually punched anyone in the face, nor pushed anyone down the escalator. I have had these intrusive thoughts before though, just like about 80-90% of the non-clinical population (summarised nicely by Clark, 2005).

Intrusive thoughts are thoughts or mental pictures that pop into our head unwanted, unintended and recurrently. They tend to interrupt our usual flow of thought and can get in the way of what we are doing. They are often thoughts which we ourselves find shocking or out of character, and they can lead to feelings of fear, horror, sadness, or negative thoughts of self-recrimination. Most people have them. Have you ever had the thought you might push someone off a train platform? Or scream in a silent exam room? Intrusive thoughts.

Psychologists Rachman and De Dilva carried out a classic study in 1978 asking people about their thoughts. 84% percent of their sample reported having unwanted thoughts that were about the sorts of things usually associated with the obsessions that people report when they have obsessive compulsive disorder (OCD) (e.g. themes of dirt or contamination, thoughts about injury, aggression, blasphemy or sex.) Another couple of studies from the late 70s, led by a psychologist called Klinger (and again summarised well here), asked students to “thought sample”: record their thoughts every time a portable alarm they carried went off. In one of these studies 22% of the students’ thoughts were self-rated as being weird or distorted. In another similar study 13% of the thoughts were self-rated as being out of character or “downright shocking”.

Intrusive thoughts are totally normal. We only have a problem if we feel that these thoughts are so awful, and mean something so bad about us, that we are compelled to do something to ‘neutralise’ them. In OCD people have a thought then usually feel compelled to carry out some kind of action in order to cancel it out. So an intrusive thought about harming others might be accompanied by a counting ritual. Or an intrusive thought about being contaminated might lead to a ritual of self-cleaning and avoiding touching or even looking at others. The heart-breaking thing is that the person is really really unlikely to ever act on their intrusive thoughts. In fact, in OCD, they are so concerned not to that they develop a whole ritualised system around it. And these rituals are the thing that gets in the way of real life, not the thoughts themselves, which most people have to some degree anyway.

So no need to worry next time you have a thought that shocks you. And no need to feel nervous if I’m standing behind you on the escalator.