Health professionals and researchers talk about 'prodromal' symptoms. Can you explain what they are?

Professor Philip McGuire: Psychotic disorders, before they are clinically obvious, there is a so called ‘prodromal phase’, where people have less specific, less obvious symptoms for a number of years. And it’s possible to identify people with these features, although it’s more difficult than identifying people with a psychotic disorder. The advantage of doing this is that you have the possibility of intervening at a much earlier stage, so before the illness has become acute and severe and it’s harder to manage.

Prodromal symptoms cover a wide range of features, so some of them are symptoms that are a bit like the typical symptoms of disorders like schizophrenia, but on a milder scale. And they are the sort of psychotic symptoms that anyone in the healthy population might experience at some time, so for example, paranoia, a feeling that people are biased against you, or out to get you, and the severity of these symptoms is less marked than you would see in somebody who was frankly psychotic.

So in practice, what that means, usually, is that there is a degree of uncertainty about it, so whereas a psychotic patient might be quite convinced that some terrible things were going on that were putting him in danger, for somebody with prodromal features, they are typically less sure and that can actually make the suspicions particularly distressing, because there’s this uncertainty and doubt, but it also means that they are potentially more open to interventions, because they are willing to take on board the possibility that these things are a function of being unwell rather, than reality.

It’s quite confusing, the terminology. Prodromal really means the sort of precursor to some illness, and that implies normally that people who have prodromal features would inevitably become unwell, but in fact it’s a bit of a misnomer because about a third of people with these features will develop a psychotic illness, but two-thirds will not. So the term prodromal is slightly misleading, in that most people who have these features, in fact, will not become psychotic and may actually recover.

So there’s another kind of terminology which refers to them as ‘high risk’ features, and that’s probably better because it conveys the idea that if you have these symptoms, you are at a much, hundreds of times higher risk than normal, but it’s not inevitable, it’s still more likely that you won’t become unwell than that you will. And that’s a very important concept in terms of the kind of interventions that you provide, because if a majority of the people who you are treating are not necessarily going to become psychotic, then whatever you do has to be as harmless as possible because they may not actually require the kind of preventative treatments you are providing.

So for example, there is a large international trial of fish oil about to start, and there is some evidence that fish oil may be beneficial in this group. The trial will clarify whether that’s the case. The potential importance of that is, that if you give someone fish oil, even if it doesn’t work in terms of preventing psychosis, it is very unlikely to do any harm. In fact it’s likely to be beneficial in terms of physical health. So that’s the kind of treatment that people are particularly interested in, in this group.