Study Finds Genetic Link To Cannabis Use Disorder

Genes might play a role in the risk of developing cannabis addiction and could be linked to an increased risk of developing several medical conditions, according to a new study.

The study conducted by researchers at Yale University School of Medicine and published in Nature Genetics early this week analyzed genes from over a million individuals worldwide, identifying genes associated with the onset of cannabis addiction.

Additionally, the study suggests a possible genetic link between cannabis addiction and a higher likelihood of developing other health conditions, such as lung cancer and schizophrenia. This implies potential unforeseen health consequences associated with cannabis use in the future, posing risks to both physical and mental well-being.

This study is crucial for understanding cannabis addiction, characterized by persistent cannabis use despite impairments in psychological, physical, or social functioning.

While cannabis is less addictive than substances like alcohol and other drugs, as shown by several studies over the years, research indicates that cannabis consumers may still develop cannabis use disorders (CUD). However, further investigation is required to comprehend these disorders, and, in this context, this study specifically identifies genes as a contributing factor to the disorder.

The study examined genomic data from over a million participants across diverse populations and identified new genetic markers linked to CUD.

“We discovered genome-wide significant loci unique to each ancestry: 22 in European, 2 each in African and East Asian, and 1 in admixed American ancestries,” the study reads.

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The term ‘loci’ is the plural of locus, which refers to a specific position of a gene on a chromosome. In the context of this study, it denotes particular locations associated with an elevated risk of CUD, helping scientists understand the genetic basis of this condition.

The study uncovered a significant role of genetic factors in CUD, indicating a link between genetics, fetal development, and CUD. It also explored connections with other traits using Mendelian Randomization (MR). A noteworthy finding was the association between CUD and lung cancer risk, raising concerns about health effects, mainly through smoking cannabis.

Researchers identified 22 significant loci for CUD in the European population, with replicated findings in genes linked to nicotine receptors.

Interestingly, the study consistently associated CUD with a specific nicotine receptor gene, CHRNA2, suggesting a common cause.

Genetic correlations revealed a two-way relationship between CUD and schizophrenia, confirmed through MR analysis—a statistical method using genetic variants to investigate causal links between factors, mimicking a randomized controlled trial design.

The study compared how closely CUD is linked to psychopathology compared to just using cannabis. It found that CUD is more strongly associated with mental health disorders.

The research also looked into chronic pain as a possible factor influencing CUD, suggesting that chronic pain might contribute to it. According to the authors of this study, this raises questions about the balance between the benefits of using cannabis for pain relief and the potential risks of developing CUD.

Additionally, the study explored the connection between CUD and lung cancer. While smoking cigarettes is known to increase the risk of cancer significantly, the study found evidence suggesting that CUD might have a one-way causal effect on lung cancer. Researchers emphasize the need to closely monitor the potential health impacts of cannabis use, especially with the growing trend of legalization.

This study has some limitations. Using electronic health records allowed for a large sample of CUD cases, but subdiagnostic cannabis use in controls may be underreported. Researchers also stated that they lacked information on THC blood levels and cannabis potency, which would be valuable for studying their effects on dependence and comorbidities. Furthermore, the study identified a causal link between multi-site chronic pain and CUD, but this may not apply to specific types of pain.

It’s worth noting that the definition of CanUD used in this study was broad, based on any report of abuse or dependence, and participants spanned a period of changing legal status for cannabis.

But despite limitations, this is the largest genetic study of CUD to date, involving over a million participants from diverse ancestral groups, from which researchers identified 25 genes and demonstrated a genetic distinction between cannabis use and CUD, with the latter being closely associated with psychopathology and disability.