Teen Marijuana Use Linked to Earlier Psychosis Onset

Pauline Anderson

May 14, 2014

NEW YORK ― Heavy marijuana use between the ages of 15 to 17 years, a period of potentially critical brain development, could result in an earlier age of onset of psychosis in those destined to develop the disorder, new research suggests.

Preliminary data from the Allied Cohort on the Early course of Schizophrenia (ACES) II project, a secondary analysis of ACES, showed that youth who used cannabis when aged 15 to 17 years experienced first episode psychosis (FEP) an average of almost 4 years earlier than their counterparts with FEP who did not use cannabis.

Any delay in psychosis onset is important because this improves outcomes in terms of severity of symptoms and functional disability, study investigator Michael T. Compton, MD, chairman, Department of Psychiatry, Lennox Hill Hospital, New York City, and professor of psychiatry, Hofstra University North Shore–LIJ School of Medicine, Hempsead, New York, told delegates attending the American Psychiatric Association's (APA's) 2014 Annual Meeting.

Predictors of age of onset of psychosis are male sex and family history of psychosis, which are not modifiable, said Dr. Compton. "My question has been, does premorbid cannabis use also drive the age of onset?"

The analysis included 247 hospitalized patients who had experienced FEP and who were generally treatment naive. Most study participants were single, male, and African American. About 44% had not graduated from high school, and almost 60% had been incarcerated. More than half were living below the poverty line.

In the study cohort, the average age of prodromal symptoms was 19.4 years, age at onset of psychotic symptoms was 21.8 years, and age of hospitalization was 23.1 years.

Dr. Michael Compton

Researchers asked each patient about marijuana use "in a very detailed way," going back to the first initiation of any use and up to the age of prodromal, psychosis, and first hospitalization, said Dr. Compton. Just fewer than 80% reported ever using marijuana.

The mean age of psychosis onset was 21.07 years in those with cannabis use from ages 15 to 17 years, compared with 23.86 years in those with no cannabis use during that age period (P ˂ .0005). For the ages of 12 to 14 years, the age of psychosis onset was 21.10 years for cannabis users during this period, compared with 22.12 for nonusers (P = .048).

The relative risk for predicting age of onset of psychosis for cannabis users between the ages of 15 and 17 years was 1.84 compared with nonusers (P ˂ .005).

Dose-Dependent Effect?

Researchers also looked at the dose or the average number of marijuana cigarettes smoked per year and found that this was also a predictor of age of onset of psychosis for those using between the ages of 15 and 17 years. This was not the case with use after age 18, noted Dr. Compton.

Dr. Compton acknowledged that it is possible that the people who are likely to have an earlier onset of psychosis are also more likely, for whatever reason, which may be related to personality, social experience, or genetics, to also be more likely to use marijuana.

"That's something my study simply cannot determine definitively," he said. "We've identified what looks like a consistent association, but at the end of the day, it's an association, and there's no way for us to prove that one is causing the other."

Critical Period of Development

Teen use of marijuana might be particularly harmful.

"Our best understanding is that those years might be particularly important and impressionable with regard to factors that trigger the onset of a psychotic disorder among people who are destined to have a psychotic disorder," said Dr. Compton.

"There is something about marijuana use in late adolescence, and to some extent in early adolescence, based on our preliminary analysis, that brings forward the age at onset that might otherwise be a couple of years later."

This, he said, is important, because any delay in the onset of a first psychotic episode can improve outcomes.

"Anything we could possibly do that might delay the onset of psychotic disorders will hugely benefit the people who end up with these disorders because the age at onset is in large part what drives the level of social disability in these illnesses.

"If you begin hearing voices in your fourth year of college as opposed to in the tenth grade, you will have accomplished a whole lot more; for example, you would have already graduated from high school, which in and of itself is associated with better physical health, better mental health, and better social outcomes, over the course of the lifespan."

Dr. Compton wants to raise awareness, especially among those at an elevated risk for psychosis, that marijuana use in adolescence may not only increase the risk for schizophrenia, according to previous research, but may also cause an earlier onset among people who are going to get the disorder.

"If we could somehow delay the onset, even if it's just by on average a couple of months or even a couple of weeks ― we would give young people a chance to accomplish more social and psychological milestones and therefore have a less severe illness."

Marijuana Use Increasing

There are "clues" as to whether a youngster is at risk that doctors can pick up on, said Dr. Compton. "Let's say a child and adolescent psychiatrist is seeing a 17-year-old with what looks like anxiety symptoms. That 17-year-old is declining in school performance, and he's already at elevated risk because his mother has schizophrenia. In this case, we need in the clinical setting to assess for cannabis use and advise against it."

Is Dr. Compton worried about the impact of marijuana legalization on vulnerable youth?

"My view is that marijuana use is not good for young people, and it's not so much because of my research on psychosis, because psychosis is a rare event. The more important issues in terms of marijuana use in adolescence is that it's associated with poorer school performance, and even academic failure and school dropouts. Not completing education is a huge public health problem."

As well, he added, marijuana use in adolescence is associated with later marijuana addiction.

"Among adolescents, I have not seen evidence of any benefits of using marijuana."

About 4% of the world's population use marijuana. Use is most prevalent among young adult men, those who are single or divorced, and whites.

Marijuana use is on the rise; from late 1990 to 2006, there was a 10% increase in global cannabis consumption, according to Dr. Compton. He added that use appears to be increasing among women.

In high school students, there has been a steady decline in cigarette and alcohol use since about 1975, but this is not the case for marijuana, said Dr. Compton. "If anything, the trend has been quite stable, if not increasing, in recent years."

Need for More Research

Medscape Medical News asked Jerome Taylor, MD, a resident in psychiatry at Yale University in New Haven, Connecticut, who moderated the APA session on marijuana use and psychosis, to comment on the findings.

Doctors, said Dr. Taylor, often see the impact of marijuana use on psychotic disorders in their everyday clinical practices.

"The ACES research underscores this link," said Dr. Taylor. "I hope that clinicians will use this data to help patients recognize the risks associated with using marijuana. Explaining the link between marijuana and psychotic disorders is especially important for patients with a family history of schizophrenia and other psychotic disorders."

But despite the growing evidence of the relationship between marijuana and psychosis, further research is needed to determine causality, added Dr. Taylor.

The study was funded by the National Institute of Mental Health. Dr. Compton and Dr. Taylor report no relevant financial relationships.

American Psychiatric Association's 2014 Annual Meeting. SCR-20. Presented May 5, 2014.

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