Risks of Underage Cannabis Use

"My study clearly shows that cannabis does not cause schizophrenia by itself. Rather, a genetic predisposition is necessary."
"It is highly likely, based on the results of this study and others, that cannabis use during adolescence through to age 25, when the brain is maturing and at its peak of growth in a genetically vulnerable individual, can initiate the onset of schizophrenia."
Dr. Lynn E. DeLisi, Harvard Medical School

Cannabis, also known as marijuana, is a product of the plant Cannabis Sativa.

"It has long been known that cannabis use can cause an acute psychotic episode in some individuals and recent epidemiologic studies suggest that frequent cannabis use in adolescents may lead to an acute psychosis that by itself develops into chronic schizophrenia. However, the majority of individuals who use cannabis do not develop a psychosis or schizophrenia. Thus, some additional mechanism must underlie the development of schizophrenia in those that are affected. If cannabis use can interact with an underlying genetic basis for the illness, changes in brain structure characteristic of patients with schizophrenia will be seen in those cannabis users who later develop schizophrenia. The brain changes may represent the genetic vulnerability for schizophrenia and be predictive of who develops the illness. Thus, Aim #1 (primary aim) of this proposal is to determine whether brain structural deviances in temporal and frontal lobes and their white matter connections will predict which cannabis users develop schizophrenia. To accomplish this we will evaluate consecutive admissions with a first psychotic episode subsequent to cannabis use admitted to two large NYC psychiatric emergency rooms. These patients will be compared with adolescent cannabis users who never had a psychotic episode, and age, sex, and social class matched non-cannabis using controls. The presence of brain structural anomalies, particularly those characteristic of patients with chronic schizophrenia psychoses will be determined by MRI scans. All cannabis using subjects will have a diagnostic follow-up evaluation one and two years subsequent to the first psychotic episode to determine who developed a diagnosis of schizophrenia or whether the initially non-psychotic individuals remained symptom-free." "Aim #2 of this proposal is to examine whether brain abnormalities among cannabis users with a first schizophrenic-like psychosis are associated with increased genetic risk for schizophrenia. This will be achieved by obtaining family information from reliable family informants. This study will ultimately have implications for early treatment strategies in adolescent cannabis users who are at high genetic-risk for psychosis and suggest early biological warning signs through MRI evaluations of individuals who have an acute psychosis following cannabis use."
Abstract:   Biological Prediction of Psychosis Susceptibility among Adolescent Cannabis Users  Delisi, Lynn Eleanor    Harvard University, Boston, MA, United States

During the teenage years of brain development unneeded connections between brain cells in the prefrontal cortex are stripped away; this is the area that controls thinking and planning. This is also the region that becomes perturbed when psychotic conditions arise, a region rich in CBI (cannabinoid) receptors involved in pruning the brain, and which become engaged by the use of cannabis. The result is the potential for alterations to the pruning process to occur. leading to an increase in the risk of schizophrenia, according to recent research. 

Circumstantial evidence exists that a biological mechanism can be triggered with the use of cannabis, causing a psychotic disorder with a tendency to emerge in late adolescence or early adulthood, matched to a period of rapid brain development. There is a realization that an inherited genetic vulnerability is involved, since psychotic conditions tend to be genetically inherited as a familial trait. Studies suggest that people are likelier to experience paranoia with cannabis use when they are already at a heightened risk of psychosis.

A study conducted in 2014 found a heightened schizophrenia risk among those with a family history, irrespective of cannabis use, leading to the understanding that familial risk for psychotic disorders outweigh possible added effects of cannabis use. According to Dr. DeLisi of Harvard Medical School, it appears likely that cannabis use during adolescence to age 25 can have the effect of initiating schizophrenia onset. However, research that might finally settle the question is scarce since marijuana has been illegal for a long period of time.

With the legalization of marijuana, policy makers and physicians are increasingly aware of the potential dangers of recreational marijuana use given that experts make a distinction between the "new cannabis" strains that are legal and far more potent now available in edibles and vapes, as opposed to the old version which comes in as a much milder weed. T.H.C., the chemical producing marijuana's narcotic effect has been rising for the past three decades. But well before then, about 70 years ago the suspicion among doctors that a link existed between marijuana and psychosis in the young existed.

Other stimulants such as caffeine, nicotine, alcohol can also be viewed as a potential cause of psychosis and hallucinogenic effects when taken in excess, just like marijuana. The temporary disorientation with peculiar imagined sights and sounds, on occasion accompanied by paranoia are the symptoms of psychosis yet the vast majority of those who experience a psychotic episode fail to develop a persistent condition such as schizophrenia, characterized by episodes of psychosis recurring for years.

The debate now ongoing revolves around the distinction between correlation and causation where people with psychotic problems often use cannabis on a regular basis, but on the other hand what is as yet unclear is which came first, the habit of using cannabis or the psychosis. And, to date, insufficient evidence exists to define whether heavy cannabis use causes schizophrenia or other syndromes. This issue is quite aside from that of possible brain damage occurring with the constant use of marijuana by under-aged users.

The end result of studies and conclusions and alternating theories rests with the issue that everyone agrees with, that the regular use of the newer, high-potency cannabis may be regarded as a risk for youth who have a family history of psychosis.