Changing Attitudes to Cannabis

Cannabis is now legalised for recreational use in 11 US states and attitudes around its risk are changing rapidly. Between 2002 and 2014, the percentage of adults in the US who perceived cannabis use as risky declined from 50% to 33%.

However, as cannabis usage becomes more widespread the health risks of the drug must be carefully evaluated, particularly as the average potency of commercially available cannabis increases. In recent years the percentage composition of the active ingredient in cannabis, THC, has risen from 4% to as high as 32%.

Research demonstrates that mothers who use cannabis during pregnancy give birth to children with lower birth weights who have increased likelihood of requiring intensive care. However, there has so far been a lack of research into fathers who use cannabis prior to having children. As 52.5% of American men of reproductive age reported cannabis use at some point in their lives, it is clear that the potential health effects on children with cannabis using fathers should be investigated.

A recent study investigated if cannabis usage in fathers could impact the health of their future children. The key to these possibly inherited effects of cannabis usage is suspected to lie in epigenetics.

The Epigenome

Epigenetic modifications are molecular ‘signposts’ that do not change the original genetic code but do change how the genes are expressed. The most common epigenetic modification is a methylation, where a methyl (CH3) group is attached to a DNA base.

Epigenetic modifications often appear due to a range of environmental factors, for example famine or chemical exposure. Previously it was thought that these epigenetic changes accumulated during the course of a person’s lifetime but could not be inherited. However, recent research has revealed that epigenetic changes can take place within the DNA of sperm cells, which would enable the epigenetic changes within the parent’s DNA to be inherited by their offspring. Studies have shown that exposure to phthalates, pesticides, nutritional deficiencies and obesity can cause epigenetic changes in the sperm DNA. The recent study showed that cannabis usage could also have this effect.

Cannabis Use and Autism

The gene for the Discs-Large Associated Protein 2 (DLGAP2) is a membrane protein that plays a key role in neuron signalling and synapse organisation. The dysregulation of the DLGAP2 gene has been associated with a range of neurological and psychiatric disorders, including autism spectrum disorder and schizophrenia.

In men exposed to cannabis, the DLGAP2 gene in the sperm displayed increased methylation. This indicates that the DLGAP2 gene could be mis-regulated in the offspring of the men if they later become fathers, and possibly leave their children more pre-disposed to psychiatric disorders. 2,077 genes in total were shown to have altered methylation in men exposed to cannabis.

Male rats were exposed to the THC before being bred with female rats not exposed to THC. The DNA in the sperm of the male rats, including the DLGAP2 gene, was found to be hypermethylated. Significant methylation was also observed in the brains of rats born to THC exposed fathers.

The Future of Legalisation

As cannabis legalisation is discussed in other countries it is the responsibility of governments to ensure the health impacts of cannabis are properly evaluated, rather that assuming its safety. This includes investigation of both the potentially inheritable effects of cannabis usage. Governments should ensure cannabis policy is underlaid by strong research to allow people to make informed decisions for themselves.

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