How exactly cannabis affects our memory- and for how long, and how significantly- is still a subject for debate. With an increasing number of studies appearing that may explain how it affects certain kinds of memory formation, as well as at different stages of brain development, much is still left unknown about both its short-term and long-term effects.
While some studies indicate that cannabis may improve memory, others show the opposite. For example, an early study looking at its effects on neurodegenerative disease, including Alzheimer's, found that it was able to slow and possibly prevent the disease's advancement by creating new neurons.
Meanwhile, other studies have shown that cannabis use may disrupt neuronal signaling and distort short-term memory processing. Other research has found that it increases a person's chances of developing false memories.
Rather than blaming cannabis for enhancing or deteriorating memory, it may be more effective to consider the substance's effects in terms of its available compounds, who uses it, and how frequently. For example, cannabis products with higher THC and less CBD have been shown to negatively impact short-term memory, especially among adolescents.
Research shows that young people who use cannabis frequently tend to have thinner temporal and frontal cortices, critical areas of the brain for memory processing. This then has a knock-on effect on motivation to learn, and thus tends to reduce young people's engagement in education.
How long this impairment remains is up for debate. Some research, for example, indicates that abstaining from cannabis use for long enough may be sufficient to completely reverse its negative effects.
Adding to the puzzle is that cannabis-use among those aged 50 or over has a comparatively smaller impact on cognitive functioning, including memory. Due to the lack of studies investigating this phenomenon, we will not understand why until further research is conducted.