The population mean drives the extreme
That is because the rise in the average means that more people end up at the ‘extreme’ level of high blood pressure, where the risks are greatest.”
This principle, ‘the population mean drives the extreme’, also applies to mental distress. We have shown scientifically that the more people in a society show symptoms of anxiety and depression, the more often full-blown mental health problems such as depression and anxiety occur. This means that the average vulnerability in a society determines the amount of severe mental health problems.
Mental disorders are connected to ordinary human emotions
So you cannot see severe cases of illness separately from the state of the people who are apparently not ill. More than that: we discovered the same principle in psychosis. Twenty years ago we already showed that the more people in a society have mild psychosis susceptibility (such as suspicion or ideas of reference), the more often severe psychosis such as schizophrenia occurs. This means that mental health problems exist on a continuum, a spectrum. What we call mental health problems is in fact connected to ordinary human emotions that we all experience.
Think of anxiety, low mood or suspicion
When these feelings become more extreme, they sometimes develop into specific forms of mental health conditions. But these extreme expressions often begin with subtler, more everyday emotions that we all know. This helps us to understand that mental distress is not something that only affects ‘the others’. It is in all of us, to the degree that we experience vulnerability, and it is deeply connected to human experience.
Psychosis is an interesting example
In urban areas, where more people live close together, we have found that the chance of psychosis is greater. The more people live per square kilometre, the higher the risk of new cases of psychosis. This is probably due to the complexity of the social environment in cities, which can sometimes be experienced as threatening.
Psychotic disorders in urban areas
What is striking is that it is not only the incidence of psychosis that is higher in cities: all people in urban areas, even those without any diagnosis, have more subtle psychotic experiences. These can be mild forms of suspicion, or quickly feeling that others are talking about them. Perhaps they sometimes hear something that is not there, or feel low or anxious for no clear reason. These are not overt psychoses, but they show that there is a spectrum from mild to severe.
This shows once again that ‘the mean drives the extreme’: the higher the average level of mild psychotic experiences in a population, the more severe psychosis we see. This insight helps us to realise that we have to see mental distress as something that affects us all, and that it is not only about the ‘severe cases’. It is about the overall state of mental health in a society.
So mental distress is, in essence, something that belongs to all of us
By recognising this, we can better understand how important it is to make room for vulnerability and mental health in our society, and to prevent the pressure on the average from pushing us towards extreme, severe forms of distress.
Prof. dr. Jim van Os, Chair Division Neuroscience, Utrecht University Medical Centre. Jim works at the interface of ‘hard’ brain science, health services research, art and subjective experiences of people with ‘lived experience’ in mental healthcare.
Jim has been appearing on the Thomson-Reuter Web of Science list of ‘most influential scientific minds of our time’ since 2014. In 2014 he published his book ‘Beyond DSM-5‘, and in 2016 the book ‘Good Mental Health Care’. In 2026 he published 'Wat psychisch lijden is'.
Want to read more?
Blogs by Jim van Os can be read here
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