Scientists find key to unwanted thoughts. The discovery may help explain why some people can't shift persistent intrusive thoughts - a common symptom of anxiety, post-traumatic stress disorder (PTSD), depression and schizophrenia.

It's not so much about avoiding an intrusive thought, but about resolving it.

As an example - a common intrusive thought is jumping from a high place. The thought may be "I could just jump off this ledge." Intrusive thoughts are theorized to be a warning system, so the thought's purpose might be your subconscious warning you about the danger of this high place - that you could jump and that would kill you. You would resolve the thought by moving away from the ledge to a place of safety. Once you're safe, and the thought is resolved, you no longer think "I could jump" and you go on with your day.

With anxiety, depression, OCD, the intrusive thoughts persist while your brain desperately tries to resolve the thought, to no avail. "I could jump" becomes a repeating echo in your mind no matter how far away you get from that ledge. You could be gripping the ground in a basement and the thought would continue. The thought becomes an obsession. From what I understand in the OP, it appears scientists have found a chemical which provides a physiological basis for this obsession.

/r/science Thread Parent Link - bbc.co.uk