By smoking weed you can not remember new things less well? That may be true for teenagers, it does not apply to elderly mice. Their learning ability and memory improved by a daily dose of cannabis, German neurobiologists saw.
Just like people, mice can remember things worse or learn new things through old age. Treatment with a low dose of THC - the most important psychoactive ingredient of marijuana - can boost the faltering memory of old mice, as well as their learning ability. In Nature Medicine, researchers from the University of Bonn and their Israeli colleagues describe how the cognition of old people after long-term use of cannabis will resemble that of young peers. Neurobiologist Andreas Zimmer led the research.
Neurobiologically, it is well mapped out how cannabis works on the brain. Our body makes its own cannabis-like substances (endocannabinoids), which bind as a key in a lock to the corresponding proteins on the cell surface of nerve cells. These proteins are called receptors; they can transmit signals when a specific molecule binds to it. Together the components form the endocannabinoid system, which humans and many species of animals need to function normally. For example, it is involved in pain, hunger, blood pressure and exercise. The weed dust THC also affects this system: it binds to the same receptors as the body's own cannabis-like substances. By using weed every day, the system can become unbalanced and, for example, pose a risk of schizophrenia in young people.
When research leader Zimmer started the study, he already knew from animal studies that the endocannabinoid system will not work as well due to age. Probably because receptors are slowly disappearing and fewer body-specific cannabis substances, such as anandamide, roam the brain. He wondered if marijuana could turn the tide.
Low dose of weed
The researchers gave a low dose of THC to young, adult and old mice every day for a month. The mice in the control group received nothing. Behavior tests followed after the treatment period. Cannabis didn't mean much to the young ones; they performed worse on learning and memory tasks than non-treated peers. The elderly and adult mice, on the other hand, became better at learning and remembering. Even until weeks after they had stopped taking cannabis.
The cognitive improvement of the old people was also accompanied by a change in the hippocampus, a brain structure that is involved in storing new memories, among other things. The pattern in which genes are switched on and off changed and again resembled the gene expression in the hippocampus of young mice.
Apparently, THC restores the activity of the receptors in the old brain, the team speculates. They write that treatment with a low dose of THC can be a strategy to delay, or even reverse, cognitive decline in the elderly.
THC good against mental deterioration, who would have expected that? Matthijs Bossong, who investigates the relationship between cannabis and schizophrenia at the UMC Utrecht Brain Center, calls the finding surprising. And a bit controversial. Cannabis is mainly prescribed as a medicine in patients with multiple sclerosis (MS) and as pain relief in terminal cancer. The scientific basis is good; THC reduces the symptoms and symptoms. "But there are concerns about the cognitive aspects of medicinal cannabis, especially in the United States, that have become more liberal in allowing it," says Bossong. "Experts point out that we do not yet know enough about any adverse effects on the brain, such as cognitive decline and the risk of addiction."
Cognitive aspects such as concentration, memory and attention have indeed not been successful in cannabis research. Previous studies have already shown that learning and memory of adolescent mice is deteriorating due to cannabis. "For young people, researchers see that smoking weed increases the risk of schizophrenia and psychosis, although it is somewhat less clear whether it is bad for cognition in the long term," said Bossong. After all that, THC now seems to be doing the cognition of the elderly well. With mice then. Whether cannabis in humans has the same effect on the aging brain? It is still too early to say anything about it.