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The University of Southampton

Research project: CBT for cannabis related psychosis

Currently Active: 

Using cannabis increases the risk of psychosis, which can include hallucinations (seeing or hearing things that are not there) and delusions (e.g., paranoia – thinking that people are trying to harm us).

This project aims to work with people with psychosis, their family and friends, and NHS clinicians, to develop psychological interventions that target these processes, in order to improve recovery outcomes for people with cannabis related psychosis.

Most people who use cannabis do not develop psychosis. However, those who are already at high risk are more likely to develop these symptoms if they use cannabis. 

It is not fully understood why cannabis leads to psychosis in some people but not others. Around one third of those with first episode psychosis use cannabis, and people with psychosis who use cannabis have worse outcomes – more severe symptoms and more hospitalisations. Cannabis can also be used to self-medicate, leading to a vicious circle of more cannabis use and more severe psychotic symptoms.

Our work shows that two key processes (thinking patterns) are likely to increase the risk of cannabis related psychosis – blaming others for unusual experiences (e.g., believing that somebody is playing a trick on me if I hear a voice), and getting caught up in difficult thoughts (e.g., not being able to stop thinking about my fears).  These thinking patterns may also explain why some people (such as those who have experienced early adversity) are more vulnerable to cannabis related psychosis.

Principal investigator: Dr Katherine Newman-Taylor

Related research groups

Centre for Innovation in Mental Health (CiMH)
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