Marijuana Use in Early Adolescence Triples Risk of Psychosis At Age 18
Hannah J. Jones and colleagues reported in the journal JAMA Psychiatry in 2018 that early- and late-onset marijuana use increased the risk of psychosis at age 18 (odds ratio 3.7 to 2.97). Interestingly, early-onset cigarette use also increased risk of psychosis, but much of the link between cigarette use and psychosis disappeared after correcting for confounding variables.
The data on 5,300 participants born from 1991 to 1992 came from the Avon Longitudinal Study of Parents and Children. Researchers followed up with the participants about their use of marijuana and cigarettes at least three times between the ages of 14 and 19.
Editor’s Note: These data add to a host of epidemiological data that smoking marijuana doubles the risk of psychosis. Risk is further increased among people with a common genetic variant (val/val) of the gene for COMT (catechol-O-methyltransferase), which metabolizes prefrontal dopamine. The variant, which includes two valine amino acids, functions better than other variants that include methionine amino acids. People with val/met or met/met COMT genes metabolize dopamine more slowly, making them relatively protected.
The data are also pretty strong that early heavy use of marijuana is a risk factor for new onset of both bipolar disorder and schizophrenia (and not just an earlier onset in those who might have been vulnerable otherwise).
While marijuana use has become more mainstream with its legalization in many states, its recreational use still carries risks of mental illness. In addition to increasing psychosis risk, marijuana use can also make bipolar disorder more difficult to treat.
A minor component of marijuana, cannabidiol, can have some positive effects, but what you get most of when consuming marijuana is tetrahydrocannabinol (THC), which produces symptoms that resemble psychosis.
Data in rats indicate that a father rat’s use of THC as an adult increases the risk that his offspring (with which he has no contact) will be prone to opiate addiction. The effect is an epigenetic one, conveyed by chemical changes in the father’s DNA that get passed on to the next generation via changes that persist in his sperm. We don’t know if this also happens with humans. So even if you are not worried about your own health, avoiding marijuana use might be good for your children.
Decriminalization of Marijuana Linked to Lower Educational Attainment
As more states pass laws allowing the use of medical marijuana, and some are decriminalizing recreational marijuana use, researchers are examining possible negative consequences of loosening these drug policies. Researcher Andrew Plunk and colleagues reported in a 2016 issue of the journal Drug and Alcohol Dependence that states where medical marijuana has been legalized have seen dropout rates increase among high school seniors. Educational attainment after high school has decreased as well.
Plunk stressed that while policies that allow medical marijuana and decriminalize recreational marijuana use may have benefits, it is also important to study any possible negative consequences of these policies. He compared marijuana to alcohol and cigarettes, substances that are legal for adults to use but also negatively impact users’ health. Plunk told Medscape Medical News that as marijuana gets approved for medical uses, kids may begin to see the drug as less risky.
Plunk and colleagues used datasets from the US Census and the American Community Survey from 1990 to 2012, which included a total of 5,483,715 people of high school age. Compared to young people in states with no legalized marijuana policies, those in states with medical marijuana had a 0.40 percentage point increase in the probability they would not receive a high school diploma or GED.
Living in a state with medical marijuana was also linked to a 1.84 percentage point increase in the probability of not enrolling in college, and a 0.85 percentage point increase in the probability of not getting a college degree.
While medical marijuana is not prescribed to minors, Plunk and colleagues believe it is easier for adolescents in states where medical marijuana is available to access marijuana that has been prescribed to adults.
Editor’s Note: Heavy marijuana use comes with risks such as doubling of the likelihood of psychosis, hastening the onset of schizophrenia and bipolar disorder, increasing cognitive impairment, and changing brain structure.
Early Marijuana Use Linked To Abnormal Brain Function, Low IQ
A study of depression and marijuana use found that using marijuana before the age of 17 was linked to abnormal brain function and lower IQ. In a 2016 article in the journal Acta Psychiatrica Scandinavica, researcher Elizabeth Osuch and colleagues described a study that compared four categories of youth: frequent pot users with depression, frequent pot users without depression, those with depression who did not use pot, and healthy individuals who did not use pot. The researchers also compared those who began using pot after the age of 17 to those who began earlier.
The main findings were that brain function in the areas of reward processing and motor control differed across the four groups. Depression was linked to deficits in brain function. Marijuana use did not correct these deficits, and in some parts of the brain, worsened them.
Those who had used marijuana before the age of 17 had abnormalities in memory, visuo-spatial processing, self-referential activity, and reward processing. Those who had started using marijuana at younger ages also had lower IQ scores.
National Academy of Sciences, Engineering and Medicine Issues Report on the Health Effects of Cannabis
In early 2017, the National Academy of Sciences, Engineering, and Medicine issued its first comprehensive report on cannabis since 1999. Shifting public opinion over the past few decades has led to 28 states and the District of Columbia legalizing medical uses of marijuana, and eight states and DC legalizing recreational marijuana use. The Health Effects of Cannabis and Cannabinoids: Current State of Evidence and Recommendations for Research is intended to address the lack of accepted standards to guide individuals in deciding whether and how to use cannabis safely. In addition to summarizing recent health-related findings on cannabis, the report also offers recommendations to guide future research.
The report shares findings about possible therapeutic benefits to cannabis use as well as health impacts relating to areas such as cancer, respiratory disease, immunity, pre- and post-natal health.
There were several notable findings with regard to mental health. The committee that issued the report found substantial evidence of a statistical association between cannabis use and the development of schizophrenia or other psychoses, with the highest risk among the most frequent users.
The committee also found moderate evidence of a link between cannabis use and increased symptoms of mania and hypomania in people with bipolar disorder who use cannabis regularly. The report also describes moderate evidence of an association between heavy cannabis use and increased suicidal ideation and suicide attempts.
There was also moderate evidence that regular cannabis use is linked to social anxiety disorder.
The report described factors that may lead to problem cannabis use. The committee found substantial evidence that being male, smoking cigarettes, and beginning cannabis use at an earlier age are risk factors for developing problem cannabis use. Read more
Continuing Marijuana Use After a First Episode of Psychosis Increases Risk of Relapse
A 2016 article in the journal JAMA Psychiatry reports that continuing to use cannabis after a first episode of psychosis increases risk of relapse. The study by Sagnik Bhattacharyya and colleagues employed longitudinal modeling to determine the role of cannabis use in psychotic relapse. The researchers followed 90 women and 130 men for two years after a first episode of psychosis, and found that the more marijuana they used, the more likely they were to have a relapse of psychosis.
Relapse rates were highest (59.1%) for participants who used pot continuously following their first episode of psychosis. Relapse rates were lower (36.0%) for those who used cannabis intermittently thereafter, and lowest (28.5%) among those who discontinued cannabis use after their first episode of psychosis.
A statistical test known as a cross-lagged analysis was used to establish that cannabis use affected later relapse, rather than relapse of psychosis leading to further cannabis use.
Another statistical strategy using fixed-effect models revealed that risk of psychotic relapse was 13% higher during times of cannabis use than during periods of no cannabis use.
These findings offer some hope that the likelihood of psychosis relapse can be reduced, since ongoing cannabis use is a risk factor that can be modified, unlike family history or genetics. Bhattacharyya and colleagues called for research into interventions that can help discourage cannabis use in people who have had a first episode of psychosis.
Editor’s Note: N-acetylcysteine, a nutritional supplement sold in health food stores, can reduce cannabis use compared to placebo in teen users.
Early Cannabis Use and BDNF Gene Variant Increase Psychosis Risk
Normal variations in genes can affect risk of mental illness. One gene that has been implicated in psychosis risk is known as BDNF. It controls production of brain-derived neurotrophic factor, a protein that protects neurons and is important for learning and memory. Another important gene is COMT, which controls production of the enzyme catechol-O-methyltransferase, which breaks down neurotransmitters such as dopamine in the brain.
Several forms of these genes appear in the population. These normal variations in genes are known as polymorphisms. Certain polymorphisms have been linked to disease risk. A study by Anna Mané and colleagues published in the Journal of Psychiatric Research in 2017 explored links between COMT and BDNF polymorphisms, cannabis use, and age at first episode of psychosis.
Mané and colleagues found that among 260 Caucasians being treated for a first episode of psychosis, the presence of a BDNF polymorphism known as val-66-met and a history of early cannabis use were associated with younger age at psychosis onset.
The val-66-met version of BDNF occurs in 25-35% of the population. It functions less efficiently than a version called val-66-val.
The researchers also found that males were more likely to have used cannabis at a young age.
Editor’s Note: In the general population, marijuana use doubles the risk of developing psychosis. Previous data had indicated that the risk was higher for those with a COMT polymorphism known as val-158-val that leads to more efficient metabolism of dopamine in the prefrontal cortex. The resulting deficits in dopamine increase vulnerability to psychosis compared to people with the val-158-met version of the COMT gene.
The new study by Mané and colleagues suggests that a common form of BDNF may be associated with an earlier onset of psychosis. Bottom line: Pot is dangerous for young users and can induce psychosis, particularly in people at genetic risk. Pot may be legal in many places, but heavy use in young people remains risky for mental health and cognitive functioning.
The company Genomind offers genetic testing for BDNF and COMT variants as part of a routine panel.
Cannabis Use May Cause Schizophrenia
Cannabis use has been linked to schizophrenia risk, and new genetic research suggests a causal relationship between the two. In a 2017 article in the journal Molecular Psychiatry, researcher Julian Vaucher and colleagues reported that lifetime cannabis use was linked to schizophrenia even when the researchers controlled for 10 genotypes weakly associated with lifetime cannabis use. This makes it unlikely that the schizophrenia caused the cannabis use, suggesting instead that it is the cannabis use that leads to a schizophrenia diagnosis.
Vaucher and colleageus also controlled for genetic associations between cigarette smoking and cannabis use to eliminate cigarette use as a third variable causing the association between cannabis and schizophrenia.
The study by Vaucher and colleagues included 34,241 people with schizophrenia and 45,604 healthy controls.
Topiramate Added to Quetiapine Can Reduce Marijuana Craving in Young People
At the 2015 meeting of the American Academy of Child and Adolescent Psychiatry, researcher Melissa P. DelBello reported that compared to placebo, the anticonvulsant topiramate reduced marijuana craving in young people aged 12–21 who were already taking the antipsychotic quetiapine. Functional magnetic resonance imaging (fMRI) revealed that topiramate altered the activation of brain regions common to both drug craving and mood dysregulation. Topiramate could be a good treatment to reduce marijuana abuse. The antioxidant n-acetylcysteine (NAC) is another option.
Marijuana Use Worsens PTSD Symptoms in Veterans
A 2015 study by Samuel T. Wilkinson and colleagues in the Journal of Clinical Psychiatry reports that among war veterans who completed a special treatment program for post-traumatic stress disorder, those who continued or began using marijuana after treatment had more severe PTSD symptoms, were more violent, and used drugs and alcohol more often. Those who stopped using marijuana or never used it had the lowest levels of PTSD symptoms in the study.
Editor’s Note: Scientific information about marijuana is almost never reported in the media. Evidence of the adverse effects of heavy marijuana use are robust and consistent.
Some of these include:
- A doubling of the risk of psychosis compared to non-users. People with a common variation in the enzyme COMT, which metabolizes dopamine, have an even higher rate of psychosis.
- An increased risk of bipolar disorder onset.
- A worse course of bipolar disorder.
- An increased risk of schizophrenia.
- Memory deficits that remain even after marijuana use has ceased.
- Loss of motivation (exactly what someone with depression doesn’t need).
- Anatomical changes in brain structures.
- A worse course of PTSD and increased violence in those with PTSD.
Bottom line: Those who say marijuana is benign may be ill-informed. People with mood disorders, proneness to paranoia, or PTSD should stay away from marijuana.
Marijuana May Speed Cortical Loss in Boys at Risk for Schizophrenia
In boys, a decrease in the thickness of the cortex is a part of normal maturation. However, according to a recent study, this process is sped up in boys at high risk for schizophrenia when they use marijuana before the age of 16.
Early use of marijuana has been linked to subsequent development of schizophrenia. Schizophrenia begins about 5 years earlier in males than in females, and the male brain goes through more structural changes during adolescence.
A 2015 article by Tomáš Paus in the journal JAMA Psychiatry incorporated data from three studies, which took place in parts of Canada and England and eight European cities. The studies all included magnetic resonance imaging (MRI) scans of the participants, a measure of their genetic risk of developing schizophrenia, and questions about their past marijuana use. In boys at high risk for schizophrenia based on their genetic profile, cortical thickness dropped more among the ones who used high amounts of marijuana before the age of 16 compared to those who did not.
Paus hypothesizes that the development of schizophrenia is a “two-hit process.” People who develop schizophrenia may have an early risk factor, such as their genetic profile or a problem that occurs in utero, and a later stressor such as drug use in adolescence.
