These findings from a new clinical trial suggest that CBT could potentially help to prevent mental illnesses before they happen in at-risk people.

The study, published in the journal The Lancet Psychiatry, was funded by the UK’s Efficacy and Mechanism Evaluation (EME) Programme, an MRC and NIHR partnership. It was carried out by researchers at the Universities of Oxford, Southampton, and Manchester.

Persecutory delusions are unrealistic beliefs that others are intentionally trying to harm the person.

This severe paranoia is a key problem in many mental health conditions, such as schizophrenia.

The 150 NHS patients in the trial had been diagnosed with schizophrenia or a related mental health problem. They all had severe paranoia, which had persisted despite medication.

Six sessions of cognitive behavioural therapy (CBT) focused upon reducing worry reduced the severity of persecutory delusions, the researchers found.

The patients were much happier and less fearful of other people after therapy. These effects lasted at least six months.

A study participant commented, 'The breakthrough was that I was able to, with the help of my psychologist, come up with a strategy – that is, when worry is gripping me I would say 'Excuse me worry, I need to interrupt you because…'. I sometime worry about people trying to harm me but now I can interrupt my worry and do something else'.

Professor Daniel Freeman at the University of Oxford, the study leader, said 'We know that worry brings implausible ideas to mind, keeps them there, and stirs up fears. It is one factor that causes paranoia. We’ve translated this knowledge into a new treatment. The clinical trial convincingly shows that teaching people how to limit worry has a major impact on long-standing fears about other people. Brief, targeted, and active psychological help makes a real difference for patients with paranoia.'

'Paranoid thinking is remarkably common in the general population, which is not surprising since every day we have to make decisions to trust or mistrust. The fears range from thinking that others are spreading malicious rumours to concerns about imminent physical attack. When paranoia gets a strong grip on a person it is typically associated with anxiety, depression, and isolation. We need much more of a focus upon problems such as paranoia. This study offers real hope and a major step forward.'

The researchers are now combining the worry reduction intervention with the targeting of factors such as sleep deprivation and low self-esteem. They aim to come up with an intervention that helps many patients recover from persistent persecutory delusions.