One of the largest earthquakes ever recorded hit on Boxing Day 2004. The resulting tsunami devastated huge swaths of the Indian Ocean coastline and left an estimated quarter of a million people dead across Indonesia, Sri Lanka, India and Thailand. Aid agencies quickly arrived to help battered and traumatised survivors.   Mental health care was a massive part of the emergency response but the World Health Organization (WHO) promptly did something it has never done before or since. It specifically denounced a type of psychological therapy and recommended that it shouldn’t be used. The therapy was a single session treatment called “ psychological debriefing,” which involved working with disaster victims to encourage people to supposedly “process” the intense emotions by talking through them in stages. It was intended to prevent later mental health problems by helping people resolve difficult emotions early on. The only trouble was that it made things worse. Studies had shown that people given post-disaster psychological debriefing were subsequently more likely to suffer mental health problems than people who had had no treatment at all.   Guidance from the world’s most influential health authority had little effect, and the therapy was extensively used. The reluctance to do things differently was tied up with some of the least-appreciated facts about our reactions to disaster. In our trauma-focused society, it is often forgotten that the majority of people who experience the ravages of natural disaster, become the victims of violence or lose loved ones in tragedy will need no assistance from mental health professionals.   Most people will be shaken up, distressed and bereaved, but these are natural reactions, not in themselves disorders. Only a minority of people — rarely more than 30% in well-conducted studies and often considerably less — will develop psychological difficulties as a result of their experiences, and the single most common outcome is recovery without the need of professional help. But regardless of the eventual outcome, you are likely to be at your most stressed during the disaster and your stress levels will decrease afterwards even if they don’t return to normal. Your body simply cannot maintain peak levels of anxiety.   These are important facts to bear in mind because, from the point of view of the disaster therapist, psychological debriefing seems to work — stress levels genuinely drop. But what the individual therapist can’t see is that this would happen more effectively, leaving less people traumatised, if they did nothing.