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 was a massive part of the emergency response but the World Health Organisation 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 reduce 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. To put icing on the rather grim cake, researchers also asked patients whether they found the technique helpful as they walked out of the door. The patients reported that it seemed useful even though follow-up assessments showed that it impaired their recovery. Even faulty life-jackets give you hope, of course. The one-off nature of the treatment just compounded the problem as it was easy for the therapists to assume that instant feedback was a guide to effectiveness.

In the light of these dangers, health agencies developed a technique called "psychological first aid" that is perhaps most remarkable for the fact that it contains so little psychology. It is really just a communication guide for dealing with traumatised people and explicitly advises against encouraging people to "process" what happened – which in itself has probably prevented a great deal of harm.

But the practice of instant psychological interventions for just-traumatised people is hard to resist. On the emotional level, professionals are drawn to "do something" to help people who are suffering. This is an admirable human motivation, though being aware of what works is a professional responsibility. We would find it less commendable if a trauma surgeon tried leeches and brandy, regardless of their good intentions. There is a slightly darker undercurrent to this, of course. The idea that rescuers can arrive in disaster areas and prevent mental illness in a single meeting is an attractive fantasy but often serves the needs of relief workers and their image more than disaster-affected communities.

It would be great if single-session treatments worked, but considering the dangers of past attempts, we would want to be sure that they were safe and helpful before we used them.

In the meantime, psychological debriefing is still widely used and new, untested single-session disaster treatments seem to be making a comeback. An article just published in the war-zone mental health journal Intervention admitted there was little evidence for the efficacy of single-session post-disaster treatments but still gave guidelines on how to do them.

With the recent tragedies of Boston, Dhaka, Syria and Mali, these issues have become newly relevant. After the chaotic response to the Indian Ocean tsunami, where truck loads of poorly informed and disorganised counsellors arrived to "treat" locals, international protocols have now been drawn up. But it's not clear how well they are being used and little is said about poor practice.

While the romantic notion of disaster rescue is attractive, the goal is to promote high-quality mental health services, based on solid research, in partnership with the community. Simply "being there" is not enough. Ironically, lots of counsellors are still not listening.