A new study from Lancaster and Lisbon Universities shows that long-term use of either cannabis or cannabis-based drugs impairs memory.
The study has implications for both recreational users and people who use the drug to combat epilepsy, multiple sclerosis and chronic pain.
Currently there is little understanding of the potential negative side effects of long-term cannabinoid exposure.
But it is already known that heavy, regular cannabis use increases the risk of developing mental health problems including psychosis and schizophrenia.
More and more people are using the drug long-term due to its legalization in several countries, while more potent varieties are available for recreational users.
Cannabis-based therapies can be very effective at treating the symptoms of chronic diseases such as epilepsy and multiple sclerosis.
But it is important to understand the side effects that users may experience so that scientists can develop new interventions to minimize these side effects.
In the study, the researchers examined the effects of the cannabinoid drug WIN 55,212-2 in mice.
They found that mice exposed to the drug long-term had strong memory impairments and could not even discriminate between a familiar and novel object.
They also found that long-term exposure impairs learning and memory in the animals.
Further brain imaging studies showed that the drug impairs function in key brain regions involved in learning and memory.
Long-term exposure to the drug impairs the ability of brain regions involved in learning and memory to communicate with each other, suggesting that this underlies the negative effects of the drug on memory.
The team suggests that this work offers valuable new insight into the way in which long-term cannabinoid exposure negatively impacts on the brain.
Understanding these mechanisms is central to understanding how long-term cannabinoid exposure increases the risk of developing mental health issues and memory problems.
They also highlighted the relevance of the work to those using cannabinoid-based therapies to treat medical conditions.
As for all medicines, cannabinoid based therapies have not only beneficial disease-related actions, but also negative side effects.
It is for the medical doctor to weight the advantages of the therapy, taking into consideration quality of life and diseases progression, against the potential side effects.
Dr. Neil Dawson is the lead researcher from Lancaster University. Professor Ana Sebastiao is the lead researcher at the University of Lisbon.
The study is published in Journal of Neurochemistry.
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Journal: Francisco M Mouro et al, Chronic, intermittent treatment with a cannabinoid receptor agonist impairs recognition memory and brain network functional connectivity, Journal of Neurochemistry (2018). DOI: 10.1111/jnc.14549.