Long-term use of either cannabis or cannabis-based drugs may impair memory, researchers said. The study may have implications for people who use the drug to combat multiple sclerosis.

Lancaster and Lisbon university researchers found that mice exposed to the cannabinoid drug WIN 55,212-2 long-term had significant memory impairments and could not discriminate between a familiar and novel object. The authors studied the effects of the drug in mice and found:

• Long-term exposure impairs learning and memory in the animals
• 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

WIN 55,212-2 is a chemical described as an aminoalkylindole derivative, which produces effects similar to those of cannabinoids such as tetrahydrocannabinol, but has an entirely different chemical structure.

Results of mouse model studies sometimes do not translate to humans. However, the researchers said cannabis-based therapies may be effective at treating the symptoms of MS and increase the quality of life for people living with the disease, but that an understanding the side effects that they may experience is needed so that they can develop new interventions to minimize these side effects. They added that it is for the medical doctor to weigh the advantages of the therapy, taking into consideration quality of life and disease progression, against the potential side effects.

The findings were published in the Journal of Neurochemistry.