In a recent research study published by the ‘Cerebral Cortex’ journal, founded that adolescences exposures to marijuana can potentially lead to schizophrenia-like changes in the brain.

Statistics from the National Institute on Drug Abuse (NIDA) showed that 15% of 8th graders have tried marijuana and over that 1% of them use it on a daily basis.

Marijuana, also known as cannabis, can induce sensations of relaxation and euphoria. However, the usage of this drug can cause anxiety, wariness, and paranoia especially with high doses and/or if the marijuana is unexpectedly potent.

Short-term effects include loss of memory, imprudence, and distortion of perception. Consequently, these short-term effects can lead to impaired performance in school or at work, and can also be an addictive habit.

Specifically in teens, marijuana affects brain systems that are still maturing and that can result into a negative and long-lasting effect on cognitive development.

Large doses of marijuana may induce acute psychosis, including hallucinations, delusions, and a loss of personal identity.

Understanding Schizophrenia:

Schizophrenia is a chronic and severe mental disorder that affects how a person thinks, feels, and behaves. People with schizophrenia may seem like they have lost touch with reality. Subsequently, society has visibly seen that schizophrenia is not as common as other mental disorders because the symptoms can be very disabling.

The symptoms of schizophrenia fall into three categories: Positive, Negative, and Cognitive.

Positive symptoms: “Positive” symptoms are psychotic behaviors not generally seen in healthy people. People with positive symptoms may “lose touch” with some facets of reality. Some of these Positive Symptoms include:

  • Hallucinations, Delusions, Thought Disorders (unusual or dysfunctional ways of thinking), and Movement Disorders (agitated body movements).
  • Negative symptoms: “Negative” symptoms are associated with disruptions to normal emotions and behaviors. Negative Symptoms include:

  • “Flat affect” (reduction of emotions via facial expression or voice tone), reduced gratification in everyday life, difficulty beginning and sustaining activities, and reduced speaking.
  • Cognitive symptoms: For some patients, the cognitive symptoms of schizophrenia are subtle, but for others, the symptoms can be much more severe as these specific patients may notice changes in their memory or other aspects of thinking. Cognitive Symptoms include:

  • Poor “executive functioning” (the ability to comprehend and apply information to make decisions), trouble focusing and/or lack of concentration, and problems with “working memory” (the ability to use information immediately after learning it).
  • Fast facts about marijuana:

  • 45% of 12th-grade students in the US have used marijuana at some time
  • 15% have used it within the last month
  • 6% use it daily.
  • Learning more about marijuana:

    These reactions are usually unpleasant but temporary; however, longer-lasting psychotic disorders such as schizophrenia have been associated with the use of marijuana.

    Most of the intoxicating effects that recreational users seek are caused by the main psychoactive – or mind-altering chemical in the drug, delta-9-TeraHydro-Cannabinol (THC).

    THC is found in resin mainly produced by the leaves and buds of the female cannabis plant. The plant contains over 500 other chemicals, of which more than 100 are chemically related to THC. Newer strains of cannabis contain higher concentrations of THC.

    Researchers from Western University in Ontario, Canada have shed light on the significant and long-term impacts of THC on the adolescent brain, after exposing adolescent rodents to THC.

    The team carried out tests in areas of behavior that are commonly observed in schizophrenia and other neuropsychiatric disorders such as social interaction, motivation, cognition, exploratory behaviors, levels of anxiety, cognitive disorganization (inability to filter out unnecessary information), and various neuronal and molecular changes.

    Using a combination of behavioral and molecular analyses within vivo neuronal electrophysiology, the team compared the long-term effects of THC exposure in adolescents and adults.

    Changes in brain resemble features of schizophrenia:

    The results from the study showed substantial and persistent behavioral, neuronal, and molecular changes that are identical to neuropsychiatric conditions, such as schizophrenia.

    ‘Adolescent rodents with THC exposure were socially withdrawn and demonstrated increased anxiety, cognitive disorganization, and abnormal levels of dopamine, all of which are features of schizophrenia. These changes continued into early adulthood, and well past the initial exposure.’

    Although the rodents demonstrated some of the behaviors mentioned earlier, no evidence of harmful and long-term effects were seen in adult rodents. Ultimately, both adolescents and adults exposed to THC experienced deficits in social cognition and memory.

    The behavioral abnormalities seen in adolescents resembled positive and negative schizophrenia-related endo-phenotypes (term used to separate behavioral symptoms into more stable phenotypes with genetic connection). A state of neuronal hyperactivity was observed in the mesocorticolimbic dopamine (DA) pathway. The mesocorticolimbic dopamine system is a pathway in the brain in which dopamine is carried from one area of the brain to another. Dopamine is responsible for controlling the brain’s pleasure and reward centers.

    Several prefrontal cortical molecular pathways were also profoundly altered. This is consistent with the sub-cortical DA dysregulation (might be associated with imbalance in the production of a particular neurotransmitter), a key characteristic of schizophrenia.

    The risk profiles for adolescents and adults were different in terms of neuronal, behavioral, and molecular markers resembling neuropsychiatric pathology.

    With amid marijuana usage amongst teenagers and the federal government moving toward legalizing it, Steven Laviolette, PhD, who led the research, sees clear implications for the findings.

    Dr. Laviolette says: “Adolescence is a critical period of brain development, and the adolescent brain is particularly vulnerable. Health policy makers need to ensure that marijuana, especially marijuana strains with high THC levels stay out of the hands of teenagers. In contrast, our findings suggest that adult usage of marijuana does not pose a substantial risk.”

    First author Justine Renard, PhD, adds that the findings helped explain how adolescent exposure to THC may lead to the onset of schizophrenia in adulthood.

    He says: “With the current rise in adolescent cannabis use and the increase in THC content, it is critically important to highlight the risk factors associated with exposure to marijuana, particularly during adolescence.”

    Medical News Today recently reported that cannabis with high levels of THC can damage brain structures, specifically in the part of the brain that aids communication between the right and left hemispheres.

    “Nature gave us the privilege of having an incredible and infinitive mind, don’t contaminate it, because will be a great loss.”


    Yvette Brazier
    National Institutes of Health