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Y Chromosome Linked To Increased Autism Risk

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Increased risk for autism appears to be linked to the Y chromosome, a Geisinger study found, offering a new explanation for the greater prevalence of autism in males. The results were published today in Nature Communications.

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by impaired social interaction and communication, and restricted and repetitive patterns of behavior, interests and activities. ASD is nearly four times more prevalent among males than females, but the reason for this disparity is not well understood.

One common hypothesis involves the difference in sex chromosomes between males and females—typical females have two X chromosomes, while typical males have one X and one Y chromosome.

"A leading theory in the field is that protective factors of the X chromosome lower autism risk in females," said Matthew Oetjens, Ph.D., assistant professor at Geisinger's Autism & Developmental Medicine Institute.

The Geisinger research team, led by Dr. Oetjens and Alexander Berry, Ph.D., staff scientist, sought to determine the effects of the X and Y chromosomes on autism risk by examining ASD diagnoses in people with an abnormal number of X or Y chromosomes, a genetic condition known as sex chromosome aneuploidy.

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Subscribe for FREE The team analyzed genetic and ASD diagnosis data on 177,416 patients enrolled in the Simons Foundation Powering Autism Research (SPARK) study and Geisinger's MyCode Community Health Initiative. They found that individuals with an additional X chromosome had no change in ASD risk, but that those with an additional Y chromosome were twice as likely to have an ASD diagnosis. This suggests a risk factor associated with the Y chromosome instead of a protective factor associated with the X chromosome.

"While these may seem like two sides of the same coin, our results encourage us to look for autism risk factors on the Y chromosome instead of limiting our search to protective factors on the X chromosome," Dr. Berry said. "However, further research is needed to identify the specific risk factor associated with the Y chromosome."

This analysis also confirms prior work by showing that the loss of an X or Y chromosome, known as Turner syndrome, is associated with a large increase in ASD risk. Further research is needed to determine whether the ASD risk factors associated with sex chromosome aneuploidy explains the sex difference in ASD prevalence.

Reference: Berry ASF, Finucane BM, Myers SM, et al. A genome-first study of sex chromosome aneuploidies provides evidence of Y chromosome dosage effects on autism risk. Nat Commun. 2024;15(1):8897. Doi: 10.1038/s41467-024-53211-7

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X Y Chromosomes

In the imprinted brain theory, everyone's brain is configured somewhere on a spectrum between hypomentalism and hypermentalism. In hypomentalism, the mechanistic, paternal genes are over-expressed, creating a baby with a larger head who demands more from the mother; this child is more likely to have autism. In hypermentalism, the mentalistic, maternal genes are over-expressed; the baby is likely to have a smaller head, demand less from the mother, and develop psychosis. The normal brain falls somewhere between the two extremes, ensuring that the child exhibits neither autism nor psychosis.

Study Finds Genetic Link To Cannabis Use Disorder

Scientist working in lab. Testing medical marijuana buds, preparing medicine.

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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.

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.

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