For a lot of teenagers smoking pot — often considered a “soft drug”— is thought of as a rite of passage no more dangerous than taking their first sip of beer or wine. And recently, legislation passed in several states legalizing marijuana for both medical and recreational use has only served to bolster public opinion that pot use, even regular pot use, is pretty benign and can alleviate certain health problems.

But a report commissioned by the National Academies of Sciences, Engineering and Medicine, released in mid January, warns against the dangers of pot use, especially in adolescence. The report cites evidence that heavy pot use, prolonged length of exposure and age at the beginning of exposure may all be risk factors in triggering a first episode of psychosis. Where mental illness — especially schizophrenia — already exists, the report concludes,  heavy and prolonged pot use may make symptoms worse.

Over the past decade, multiple studies have shown that marijuana use in adolescence can be a contributing factor in triggering or worsening the symptoms of serious psychotic mental illnesses, most notably schizophrenia. But studies have also found that young people with a predisposition to developing a psychotic illness may be drawn to pot at an earlier age — possibly as a form of self-medication — than other adolescents. So it goes both ways.

The report, which assessed more than 1,000 studies, emphasized how little is still known about the health effects of marijuana, calling the lack of scientific information “a public health risk,” especially when it comes to the effects of marijuana on the developing brains of adolescents. “We need more data,” says Dr. Michael Birnbaum a child and adolescent psychiatrist and director of the Early Treatment Program at Northwell Health. Because Dr. Birnbaum treats early psychosis and works with young adults with schizophrenia, he notes, “inevitably pot, and drugs, and alcohol become a part of the conversation.”

Can pot use cause schizophrenia?

 Maybe, maybe not. “I would not want to tell my patients that it was one joint, for example, that caused their psychotic illness,” says Dr. Birnbaum. “I work with young folks who have been smoking heavily  for the past several years, and I still wouldn’t confidently say that  the pot caused schizophrenia. That’s just a dangerous thing to say.”

Developing a psychotic illness is multifactorial, says Dr. Birnbaum. “It’s never just one thing.”

On the other hand, both heavy use and an increase in use from occasional to daily — as well as earlier and longer exposure to pot — have been linked to psychosis. “Evidence suggests that pot smoking can lead to earlier onset — that it can develop it sooner than it would have otherwise,” says Dr. Birnbaum. “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 that, he says is “ hard to prove for sure and we don’t have a specific number of joints, a specific dose of cannabis, that we know is likely going to trigger a psychotic experience.”

Dr. Birnbaum gets this question from his patients a lot: if I’d never smoked pot, would this have still happened to me? And, he says it’s a question that’s virtually impossible to answer.

What we do know

 Michael T. Compton, MD, MPH, a professor of clinical psychiatry at the Columbia University College of Physicians and Surgeons, has conducted a number of studies and meta-analyses focusing on the association between first episode psychosis and cannabis use. The two studies Dr. Compton and his colleagues conducted involved, respectively, 109 and 247 hospitalized first-episode psychosis patients.

“Very detailed and rigorous retrospective data were collected on the onset of prodromal and psychotic symptoms, as well as the initiation and escalation of nicotine, alcohol, marijuana, and other drug use,” says Dr. Compton. The results?  Both studies revealed an association between the escalation of marijuana use and an earlier age at onset of prodromal symptoms and an earlier age at onset of psychotic symptoms.

“These findings,” Dr. Compton says, “suggest that adolescent/premorbid marijuana use is not only a risk factor for the later development of primary psychotic disorders (which has been shown in prior studies), but is also a risk factor for an earlier onset of those disorders.”

Age of onset matters because studies show that the long-term outlook for a person with schizophrenia is better the later the disorder develops. Dr. Compton’s studies also fortified the idea that age at onset is “a crucial prognostic indicator for the long-term course of schizophrenia and other psychotic disorders.”

Will stopping cannabis use end psychosis? 

While less frequent use of marijuana reduces the risk of a first psychotic episode, it doesn’t follow, unfortunately, that for someone who does develop schizophrenia, cutting it out would eliminate the disorder. Schizophrenia and other psychotic illnesses are long-term  mental illnesses that need to be managed, Dr. Birnbaum notes. “If pot turns on that switch, it’s not something that can be easily turned off,” he says. “Marijuana could effectively trigger a primary psychotic disorder, meaning that even once the substance is removed, the symptoms are still there.”

How much is too much?

 When it comes to pot and psychosis, moderation does matter. But it’s impossible to tell how big a risk you might be taking if you begin to light up on a regular basis.

The best recommendation Dr. Birnbaum can provide for would-be or current pot users is that if they have an unusual hallucinations or other psychotic-like experiences while intoxicated, it’s an indicator that they may have a predisposition to some kind of psychotic illness. For them it would be better to be cautious and to avoid substances.

Clearly there is still a lot to learn and much research to be done. But the federal government has, for decades, made this difficult for scientists. According to the recently released report, that’s at least partly because the federal drug enforcement agency’s designation of the drug as a Schedule I substance — defined as having “no currently accepted medical use and a high potential for abuse” — entails so many restrictions that it has been difficult for researchers to do rigorous research on marijuana.

What can parents do?

 The best thing parents can do is arm their kids with the facts — not scare tactics or threats, but the facts: that occasional or infrequent use of pot is much safer than regular use and that daily use could be setting them up for real trouble. And that we just don’t know enough about the risks to the developing adolescent brain and the long-term effects of marijuana.

“It’s a very hard conversation to have, especially for young folks in a developmental stage where they think that they’re invincible,” Dr. Birnbaum says. “Drugs and alcohol are prevalent in adolescence, young adulthood, and also in some ways, it is sort of a rite of passage. It’s something that many people do, and many people don’t have any issues as a result.”

This ongoing conversation is one that parents should start early since the report also notes that that the evidence suggests that initiating marijuana use at a younger age, “increases the likelihood of developing dependency, which can affect academic performance and social interactions.”

Open, honest and frequent dialogue is Dr. Birnbaum’s best advice to parents. Ultimately it’s going to come down to what your child comes to think is in his or her best interest and how they act on that. “The child,” he says, “should be really well informed.