Experts warn of a psychosis explosion – rising cases of the mental condition linked to murders and violent attacks associated with ‘ageing parents’ and cannabis use

A new study has noted a concerning surge in young people being diagnosed with psychotic illnesses such as schizophrenia. 

Research carried out by Canadian researchers looked at hospital data associated with 12.2 million people born between 1960 and 2009 who live in the province of Ontario. 

Of this cohort, about 152,000 were diagnosed with a psychotic disorder – classed as either schizophrenia spectrum disorders (SSD) or psychosis ‘not otherwise specified’ (psychosis NOS) – and of these, there was a distinct increase in cases seen in people born from 1980 onwards.

The data revealed that new diagnoses in teenagers and young adults aged 14 to 20 rose by 60 per cent between 1997 and 2023.

Those born between 2000 and 2004 were estimated to be 70 per cent more likely to be diagnosed with schizophrenia than people born in the late 1970s. 

Schizophrenia is a chronic mental health condition characterised by psychotic episodes where individuals lose touch with reality, experiencing delusions and hallucinations. 

The researchers – from ICES, North York General, Ottawa Hospital Research Institute, and Bruyère Health Research Institute – looked at the amount of people who had been diagnosed with the mental illness by the age of 30, and found that those born in the early 1990s were 38 per cent more likely to have a psychosis diagnosis compared with people born in the late 1970s.

A person was counted as having a psychotic disorder if they were discharged from hospital with a psychosis diagnosis, or had at least two outpatient doctor visits within a year which were coded by physicians as psychosis.  

The data did not include psychosis caused purely by a mood disorder such as bipolar, brief psychotic reactions that never led to medical care or drug intoxication alone without a psychosis diagnosis.

Psychosis is a serious mental illness where a person loses touch with reality, often involving symptoms like hallucinations and delusions which can cause them to pose a danger to themselves or others. 

The findings, published in medical journal CMAJ, suggest that people born in more recent decades are being diagnosed with psychotic illnesses more often and at younger ages than people born earlier. 

Overall, men were found to be more likely to develop psychosis than women, and people with schizophrenia were more likely to be from a lower socioeconomic background or already have had treatment for mental health problems or substance use. 

Lead author Dr. Daniel Myran said: ‘Consequently, the observed trends raise important questions about possible causes and consequences of increasing numbers of psychotic disorder diagnoses.

‘We don’t yet know what’s driving these changes, and it’s likely there isn’t a single explanation. Understanding what’s behind this trend will be critical to prevention and early support.’ 

He added that one possibility for the surge in psychotic disease is the use of drugs, particularly cannabis – adding that there is an undeniable correlation between an increase in substance use in Canada and the findings.  

‘A leading possibility is substance use — including cannabis, stimulants, hallucinogens, and synthetic drugs,’ he said. 

‘The use of substances, especially earlier in life, is associated with the development and worsening of psychotic disorders, and substance use in Canada has risen over the past two decades.’

Figures show cannabis is consistently the most consumed illegal drug in England and Wales, with 2.3 million people estimated to have used it in the year to March 2024.

Research, published in 2024, shows adolescents who used it were 11 times more likely to have a psychotic episode as an adult.

Other potential causes mooted by the researchers include an increase in social and financial stress and difficult or traumatic childhood experiences. 

Another possible cause could be that parents are having their children later in life, which raises concerns about sperm and egg quality. 

It’s also important to note that improved diagnostics and understanding of the condition could have led to higher numbers of diagnoses – but more investigation is needed. 

The research comes amid a surge in grisly crimes blamed on psychosis.

Last August, a leading psychiatrist warned that cannabis-induced psychosis is becoming increasingly common across the UK.

The widely used class B drug – also known as marijuana or weed – can cause dependency, and while regular use has more than halved in the past two decades, the number of cannabis-induced psychosis episodes has spiked as varieties on sale have become stronger.

Dr Niall Campbell, a consultant psychiatrist at the Priory rehabilitation centre, warns of a deepening public health issue, stemming from easy online access to highly potent forms of the drug known as ‘skunk’. 

Made from unpollinated cannabis plants which naturally contain higher levels of THC – the main psychoactive ingredient – skunk greatly increases the risk of paranoia and hallucinations.

‘There has been a visible rise in the number of people needing intensive support for psychosis as a result of cannabis use,’ said Dr Campbell. 

‘I don’t think this is surprising given how easy skunk is to buy. What begins with smoking a few ‘joints’ and feeling a bit paranoid can easily escalate. 

Over time people can reach a psychotic state which won’t go away, even if they stop smoking – they can become very depressed or suicidal.’

In April 2024, Marcus Monzo, 37, of West Beckton, Newham murdered a schoolboy while in a cannabis-induced psychotic episode. 

Monzo killed and skinned his own cat before hacking 14-year-old Daniel Anjorin to death ‘in an instant’ with a samurai sword, and left four others seriously injured. 

And last year, Sekai Miles, 23, beat 87-year-old grandfather Bernard Fowler to death with his own walking stick eight months after being discharged into the community by mental health services. 

Miles was diagnosed with paranoid schizophrenia, a condition ‘exacerbated’ by his cannabis use.