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Adolescence cannabis use: Risk for Schizophrenia

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Drug addiction is a serious socioeconomic problem associated with significant mortality and morbidity. this study highlighted the complex relationship between drug-induced neuroadaptations in the brain and addictive behaviors using examples from both human studies and animal models. these neuroadaptations thought to be responsible for the transition to a persistent state of addiction. addiction is a highly integrated process complicated by differing profiles the drug themselves. this, of course, includes the use of cannabis by youngsters. it has been shown to open the adolescents up to not only addiction but mental illnesses as well (Duncan, 2012).


Victorian Adolescent Health Cohort Study is a long-term Australian study that has documented cannabis use in young Australians from mid-teens to the mid-30s. In the 1920s the Geneva Convention ratified international drug control and included Indian hemp despite a lack of conclusive evidence then of harmful consequences. Some 70 years later, there has developed two camps about how harmful cannabis is to adolescents.

This study follows cannabis users from adolescence to adulthood. It is well established that first-time use of cannabis often occurs during adolescence with the heaviest use between late adolescence and young adulthood. The study found cannabis has become very common with the adolescent group. In this study, 62% of participants reported using cannabis at least once during follow-up from 14 to 35 years with half commencing whilst of high school age and further 38% before they were 20 yrs.

It was found that males were more often than females to start use and would escalate with peer pressure. The definition of dependence was relaxed in the DSM-II (Diagnostic and Statistical Manual of Mental Disorders) publication. Due to this cannabis can be classified as a drug of dependence; although it only received cursory attention for the next 35 years. When the DSM-IV came out the study again identified criteria for a 12-month diagnosis of dependence in the adult group.

Cannabis and tobacco use was found to be closely linked. Adolescent tobacco smoking was found to be at risk for cannabis use in adolescence. A consistent association was noted between depression and cannabis use in adolescence and young adulthood, but the relationship weakened as they matured into young adults. Females using daily in adolescence or at 20years were shown to be more likely to report anxiety and depression symptoms at 20 years than were non-users. The links with poor mental health despite later abstinence suggests a possibility of partially irreversible neurotoxicity with heavy early adolescence use. They were also able to confirm with this study, that in adolescence, other risk behaviors such as cigarette smoking and antisocial behavior are often associated with the initiation, continuation, and escalation of cannabis use (Coffey & Patton, 2016).

Cannabis use is increasingly pervasive among adolescents today, even more, common than cigarette smoking. The evolving policy around the legalization of cannabis reaffirms the need to understand the relationship between cannabis exposure early in life and psychiatric illnesses. Cannabis contains psychoactive components notably THC that interferes with the brain’s endogenous endocannabinoid system. This system is critically involved in both pre- and post-natal neurodevelopment.

Consequently, THC and related compounds could potentially usurp normal adolescent trajectory toward a disease-vulnerable state predisposing early cannabis users to motivational-affective and psychotic disorders. Numerous studies have been done demonstrating that early cannabis use is associated with the major depressive disorder and drug addiction. In addition, a strong association between cannabis use and schizophrenia has also been found.

Given the vulnerable nature of adolescent neurodevelopment and the persistent changes that follow early cannabis exposure-the findings should be carefully studied and considered by policymakers. In the US cannabis use is highly prevalent during adolescence with over 6000 first time cannabis users per day [2013]. Over 60% of which were under the age of 18. Determining the long-term impact of occasional and heavy cannabis use during active periods of brain development such as adolescence is of critical importance.

Emerging evidence strongly suggests cannabis exposure during adolescence increases an adult’s individual vulnerability to drug addiction and schizophrenia and may also produce long-lasting effects on anxiety and mood disorders. Although a relationship between marijuana’s glamorization and the increasing use of it in teenagers, important lessons can be learned from major inroads make to decrease cigarette smoking. The current evidence does show cannabis use during adolescent development increases the risk of psychiatric disease when adult (Chadwick et al, 2013).

Cannabis is the most recently used illicit substance across the globe and has a long-standing history in many cultures for its euphoric and psychotropic effects. The biochemical mechanism by which cannabis exerts its effects on physiology and behavior remained a mystery until the components of cannabis were extracted and THC was found to be the psychoactive part of cannabis. In the early 1990s, the cannabinoid receptor was genetically determined and its distribution was then mapped in the brain.

Its distribution is widespread in the brain with high densities in several brain regions like the hippocampus and cerebellum. The hippocampus is located in the inner region of the temporal lobe and is important for regulating emotional responses. The cerebellum is a section of the brain located at the back of the brain below the cerebrum. It coordinates sensory input with muscular responses. It also plays an important part in maintaining balance and posture.

The study also found moderate to low densities in the amygdala, midbrain, and cerebral cortex. During the early phases of neuronal development, endocannabinoid signaling is important for an array of processes including proliferation and differentiation of progenitor cells, neuronal migration, axonal guidance and positioning of cortical interneurons. In utero exposure to THC hampered the appropriate interneuron positioning during corticogenesis resulting in an increased density of CCK-positive interneurons in the hippocampus. Schizophrenia is increasingly viewed as a subtle neurodevelopmental disorder characterized by disrupted brain connectivity and altered circuitries. The periods of brain development includes the time of adolescence.

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In fact, neurodevelopmental views of schizophrenia say that the illness may result from either an early static brain lesion with a long latency or a late (adolescence) brain disturbance of limited duration and short latency. Lifetime use in 12th-grade students in the US was 49% in 2007 while in 2008 over 15% of 12th-grade students reported using cannabis daily for at least a month at some point in their lives.

The belief that cannabis can induce psychotic-like symptoms has been reported for over 50 years. In individuals with a predisposition for schizophrenia ingesting cannabis worsens symptoms and worsens the prognosis. Epidemiological evidence suggests cannabis use is a risk factor for schizophrenia and the use of cannabis in people already predisposed to schizophrenia makes the symptoms worse and worsens the prognosis. The neurodevelopmental characteristics of adolescence create a more vulnerable circumstance for cannabis to produce psychotic-like symptoms and possibly cause schizophrenia (Malone et al, 2010).

Schizophrenia is a devastating mental condition characterized by psychotic manifestations, including delusions and hallucinations. Although studies can provide important insights into the biological mechanism underlie part of the pathology of schizophrenia. Environmental stressors like cannabis use may contribute to schizophrenia.

This disorder can be a complex genetic disorder characterized by large inter-patient variations. Strong evidence has been gathered that links schizophrenia aberrant neuronal activity. Intra-patient and inter-patient variability are two additional types of variables. Intra-patient exists because individual lines vary genetically and show a propensity to neural differentiation. By modeling specific aspects of schizophrenia rather than capturing the entire diversity of this disorder.

It is now time to bring together the fields of neurobiology and human genetics. By examining the effects of genetic variants we can assay gene pathways in specific in whom a novel lesion was identified. Beyond mechanistic insights into schizophrenia, there is now a platform for identifying new therapies. But all this affords medicine is a way to track which adolescent who takes cannabis will develop mental health issues as they age and continue their use of this drug (Brennard et al, 2014).

Consistently imaging studies have shown altered activity in the amygdala, hippocampus, basal ganglia, and prefrontal cortex. These areas are involved in stress responsiveness, emotional reactivity, goal-directed behavior, motivation, and executive function. This material produces behavioral effects akin to schizophrenia and bipolar disorder. These effects include distortion of sensory stimuli, dysphoric behavior, depersonalization, speech, and language impairments (Tejeda et al, 2012).

Works Cited
Brennard, K.J., Landek-Salgado, M.A. & Sciwa, A. (2014). Modeling heterogeneous patients with a clinical diagnosis of schizophrenia using induced pluripotent stem cells. Biological Psychiatry, 75(12). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4022707/

Chadwick, B., Miller, M.L. & Hurd, Y.L. (2013). Cannabis use during adolescent development: Susceptibility to psychiatric illness. Frontiers in Psychiatry,4(129). https://www.frontiersin.org/articles/10.3389/fpsyt.2013.00129/full

Coffey, C. & Patton, G. (2016). Cannabis use in adolescence and young adulthood. The Canadian Journal of Psychiatry,6(6). http://journals.sagepub.com/doi/pdf/10.1177/0706743716645289

Duncan, J.R. (2012). Current perspectives on the neurobiology of drug addiction: A focus on genetics and factors regulating gene expression. International Scholarly Research Network Neurology. https://www.hindawi.com/journals/isrn/2012/972607/

Malone, D.T., Hill, M.N. & Rubino, T. (2010). Adolescent cannabis use and psychosis: Epidemiology and neurodevelopmental models.British Journal of Pharmacology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2931552/

Tejeda, H., Shippenburg, T.S. & Henriksson, R. (2012). The dynorphin/K-opioid receptor system and its role in psychiatric disorders. Cellular and Molecular Life Science,69(6). https://www.researchgate.net/profile/Hugo_Tejeda/publication/51719655_The_dynorphink-opioid_receptor_system_and_its_role_in_psychiatric_disorders/links/0a85e5329922312d4d000000/The-dynorphin-k-opioid-receptor-system-and-its-role-in-psychiatric-disorders.pdf