You can often hear that smoking cannabis makes a person distracted and forgetful. Let's see what is really known about this. Will the memory return to a person who smokes it only on public holidays?
The paradox of the effects of marijuana for memory
For a long time, information about the effects of marijuana on memory was based not on qualitative research, but on descriptions of isolated cases. Data that have been obtained in recent years have turned out to be unexpectedly contradictory.
As expected, immediately after using marijuana, short-term memory may be impaired, and its processing in the brain may be affected. This is accompanied by a decrease in the ability to concentrate. It has been found that these effects can last several days or even weeks and are completely reversible.
At the same time, there is evidence of improved memory after using marijuana and its components for medical purposes for a number of serious illnesses. This has been shown in humans for epilepsy, and in animals for Alzheimer's disease.
A Tale of Two Substances
Marijuana contains more than 100 cannabinoids. The most important representatives of this group of psychoactive substances for our story are tetrahydrocannabinol (THC) and cannabidiol. These substances can be called antagonists of sorts. The first, by binding to cannabinoids in the brain, causes the feeling of euphoria characteristic of marijuana use. The second one competes with THC for these receptors: by binding to them, it prevents the onset of drug intoxication. This component of marijuana improved memory in the examples above.
In recent years, there has been a trend towards increasing the concentration of THC in marijuana. In different varieties, the ratio of THC and cannabidol may differ, affecting its effects.
THC is responsible for the acute memory impairments we wrote about above. It binds to receptors in those parts of the brain that play an important role in memory formation (hippocampus, amygdala and cortex). The ability to both “retain” new information and remember what is already known suffers. The study found that marijuana with a high percentage of THC is responsible for short-term memory impairment in adolescents who use it.
Does age play a role
Another paradox is the positive effect of THC on the memory of elderly mice. Scientists suggest that as we age, the structure and function of neuronal connections in the brain may change. In the future, we may learn unexpected things about the effects of marijuana on older people. However, today it is difficult to draw firm conclusions about how memory is affected by marijuana use at different ages.
A study has found that adolescents who use marijuana may experience thinning of the parts of the cerebral cortex responsible for memory. But today there is no high-quality evidence that their memory is truly irreversibly damaged. The poor academic performance of adolescents who use marijuana may be explained by their decreased motivation for schoolwork.
Similarly, very little is known about memory changes in people over the age of 50. Research has been done in this area, but the data is mixed.
What happens if you use marijuana for a long time
Research into the effects of long-term marijuana on memory is difficult because it is difficult to take into account all the associated factors. For example, if a person, in addition to smoking cannabis, likes to drink, then it is not easy to establish exactly why his memory is impaired. On the other hand, people who use psychoactive substances may exaggerate or underestimate their use because they are prone to false memories (twice as likely as nonsmokers).
Current scientific evidence suggests to say only that long-term marijuana use is likely associated with slight memory impairment. With accidental, irregular use, irreversible changes in memory do not occur. Scientists suggest that, based on current knowledge, it is no longer possible to clearly blame marijuana for memory impairment. It is necessary to take into account its types and concentrations of various active substances in it.