Cannabis use may lead to false memories: study

Cannabis users are more likely to have distorted memories and can even end up imagining situations that actually never happened, a new study has found.
One of the known consequences of consuming this drug is the memory problems it can cause. Chronic consumers show more difficulties than the general population in retaining new information and recovering memories, researchers said.
The study conducted by researchers at the Biomedical Research Institute of Hospital de Sant Pau and from Universitat Autonoma de Barcelona also shows that the chronic use of cannabis causes distortions in memory, making it easier for imaginary or false memories to appear.

On occasions, the brain can remember things that never happened. Our memory consists of a malleable process which is created progressively and therefore is subject to distortions or even false memories.
These memory "mistakes" are seen more frequently in several neurological and psychiatric disorders, but can also be observed in the healthy population, and become more common as we age.
One of the most common false memories we have are of situations from our childhood which we believe to remember because the people around us have explained them to us over and over again.

Researchers compared a group of chronic consumers of cannabis to a healthy control group while they worked on learning a series of words.

After a few minutes they were once again shown the original words, together with new words which were either semantically related or unrelated.
All participants were asked to identify the words belonging to the original list.
Cannabis consumers believed to have already seen the semantically related new words to a higher degree than participants in the control group.
By using magnetic resonance imaging, researchers discovered that cannabis consumers showed a lower activation in areas of the brain related to memory procedures and to the general control of cognitive resources.
The study found memory deficiencies despite the fact that participants had stopped consuming cannabis one month before participating in the study.

Although they had not consumed the drug in a month, the more the patient had used cannabis throughout their life, the lower the level of activity in the hippocampus, key to storing memories, researchers said.
The results show that cannabis consumers are more vulnerable to suffering memory distortions, even weeks after not consuming the drug.
This suggests that cannabis has a prolonged effect on the brain mechanisms which allow us to differentiate between real and imaginary events.
The study was published in the journal Molecular Psychiatry.