A new study has thrown into question the link between cannabis use and the development of psychosis spectrum symptoms in adolescents – though not in the way you might be hoping for. While the association between the two factors remains solid, what is now less certain is the direction between them – in other words: does cannabis use cause psychosis, or vice versa?

Depending on who you ask, cannabis is either a wonder drug that can treat everything from to seizures to public road safety itself – or else it’s a brain-warping, IQ-lowering gateway to hard narcotics which might just make you temporarily lose your mind and cut your own dick off.

Wherever you fall on that spectrum, however, some things are inarguable. Such as: using cannabis as a youngster has consistently been linked to higher incidences of psychotic disorders such as schizophrenia – and, frankly, it’s probably not a coincidence. 

“Evidence suggests that pot smoking can lead to earlier onset” of psychosis, according to Michael Birnbaum, a child and adolescent psychiatrist and director of the Early Treatment Program at Northwell Health, who was not involved in the new study. 

In other words, “it can develop it sooner than it would have otherwise,” Birnbaum told the Child Mind Institute. “In addition, pot is also associated with development of illness in otherwise healthy individuals, meaning it is possible that psychosis would not have developed in that person if they had never smoked pot.”

But a question that’s much more difficult to answer – and the one that the team behind the new paper attempted to shed some light on – is this: how many of those cannabis users who do have symptoms of psychosis were actually experiencing the link the other way around?

“Cannabis use [is] associated with a higher risk of psychosis,” the researchers explained in a statement. 

But “the link between cannabis use as a young person and increased psychosis spectrum symptoms could be partially due to young people with those symptoms self-medicating with cannabis,” they said.

Using data from the Adolescent Brain Cognitive Development, or ABCD, Study – a large-scale, longitudinal study of brain development and mental and physical health of children in the US, which was launched in June 2016 and is still ongoing – the team were able to track the incidences, intensities, and onset of both psychosis symptoms and cannabis use in close to 12,000 young people over the course of four years.

And the results were notable – especially for those studying the effects of cannabis use and misuse. “The evidence was mixed around whether beginning to use cannabis was linked to increasing symptoms,” the researchers found – but there was “clearer evidence of psychosis-related symptoms increasing in the lead-up to first using cannabis.”

It’s important to note that, as an observational study, no causal links can be concluded – basically, we can’t say for sure that psychosis symptoms is what’s making kids pick up the blunts – but the researchers nevertheless believe that it’s worth taking note of. 

“We should account for the possibility of some teens self-medicating because of existing symptoms when trying to understand the link between cannabis and psychosis,” the statement says.

The study is published in the journal JAMA Psychiatry.