The association between marijuana use and an increased risk of psychiatric disorders has been the subject of much debate. Past research has established a link between frequent marijuana use during adolescence and an increased risk of psychotic-like experiences (PLE), psychosis, bipolar disorder, depression and schizophrenia. However, uncertainty exists regarding the underlying mechanisms of such associations. Researchers from the National Institute on Alcoholism and Alcohol Abuse (NIAAA) recently conducted a study to understand brain functioning in heavy marijuana users.
The researchers recruited 441 adults aged 22-35 for the study. These included 30 cannabis abusers and 30 healthy controls. Functional MRI (fMRI) was used to examine the “resting-state brain function” of the brain’s subcortical regions. Results of the study, published in the journal Biological Psychiatry: Cognitive Neuroscience and Neuroimaging (BP:CNNI) in November 2017, showed that chronic cannabis abuse was associated with alterations in resting-state brain function, “particularly in dopaminergic nuclei implicated in psychosis, critical for habit formation and reward processing.”
The researchers noted that brain’s hyper-connectivity in four specific subcortical regions was most prominent in individuals who started “marijuana use earliest in life” and who reported “high levels of negative emotionality.” In particular, it was found that symptoms of alienation – a negative emotionality – were strongly associated with high subcortical connectivity in people who abused cannabis and had “aberrant brain function.” The researchers specifically focused on alienation (a perception that others wish harm or want to deceive one) since their previous research on cannabis abusers had found similar results.
Adolescent cannabis abuse linked to psychiatric disorders
The study emphasized that cannabis abuse in adolescence was particularly harmful since the brain was in a critical state of development. The researchers referenced past research which had established that persistent cannabis use during adolescence was associated with neuropsychological decline from childhood to midlife. This decline was observed even after factoring in years of education and more persistent use was associated with a greater decline. Moreover, discontinuation of cannabis use did not fully restore neuropsychological functioning among individuals who had started using the drug during adolescence.
Recently, another study found an association between frequent marijuana use by 17-year-olds and hypomania (a symptom of bipolar disorder) during early adulthood (ages 22-23). The severity of the association depended on the dose; weekly marijuana use had a stronger association with hypomania than “any use.” Similarly, a past study attempted to investigate the association between smoking marijuana and schizophrenia. Although conclusive evidence could not be found, the results suggested a partial association due to a shared genetic etiology.
The study was particularly relevant to the United States where marijuana is the most commonly used illicit substance and the third-most frequently abused substance by adolescents after alcohol and tobacco. The drug causes impairments to short-term memory and learning, the ability to focus, and coordination. Although recent data showed that the legalization of medical marijuana had led to a decline in adolescent (12-17 years) pot use, its use appears to be increasing in young adults aged 18-25 and adults aged 26 years and above.
Co-occurring substance abuse and mental illnesses
Cameron S. Carter, editor of BP:CNNI, said that the brain imaging data established an association between “changes in brain systems involved in reward and psychopathology and chronic cannabis abuse.” According to him, the findings suggested a mechanism whereby heavy use of the “popular drug” could lead to depression and other severe mental illnesses.
When substance abuse and mental illnesses occur simultaneously, it is called a co-occurring disorder or dual diagnosis. In 2016, nearly 0.3 million adolescents aged between 12 and 17 years (1.4 percent of the age group) had a co-occurring substance use disorder (SUD) and major depressive episode (MDE). More than 24 percent adolescents with MDE reported using marijuana during the year.
Adolescents who experience troubling symptoms of substance abuse and co-occurring mental illnesses need specialized care. Sovereign Health of Rancho San Diego, a leading substance abuse and behavioral health treatment facility in the U.S., offers state-of-the-art dual diagnosis rehab for teens aged between 12 and 17 years. To find out more about our dual diagnosis rehab centers for teens, call our 24/7 helpline or chat online with our experts.