Cannabis, commonly known as weed, has long been associated with changes in cognitive function, particularly in memory. One of the most consistent findings in neuroscience is that cannabis use can impair short-term memory, especially during acute intoxication. This article explains the scientific mechanisms behind that effect.

The key component responsible for this impact is tetrahydrocannabinol (THC), the primary psychoactive compound in cannabis. THC mimics the action of naturally occurring neurotransmitters called endocannabinoids, which play a role in regulating mood, appetite, pain, and memory. These endocannabinoids normally bind to receptors in the brain known as cannabinoid receptors, especially the CB1 receptor.

The CB1 receptor is highly concentrated in the hippocampus, a brain region critically involved in forming new memories. When THC binds to CB1 receptors in this area, it disrupts normal signaling patterns and interferes with the brain’s ability to encode and store new information. This results in difficulty forming short-term memories or retaining information that was recently learned.

Research using brain imaging and electrophysiological techniques has shown that THC reduces neural activity in the hippocampus and weakens the synaptic plasticity required for memory consolidation. Specifically, THC suppresses long-term potentiation (LTP), a process by which synaptic connections are strengthened—a necessary step for storing memories.

Importantly, the effect of cannabis on memory is typically transient. Most users experience these impairments only during the period of intoxication, and memory function usually returns to normal once the drug has worn off. However, in heavy or chronic users, especially adolescents whose brains are still developing, these effects may be more persistent or even lead to long-term cognitive changes.

THC also affects attention and working memory, which are essential components of short-term memory. By impairing focus and the ability to track multiple pieces of information, THC makes it harder to perform tasks that require sustained mental effort or recall of recently learned material.

In summary, weed causes short-term memory loss by disrupting the brain’s endocannabinoid system, particularly through the action of THC on CB1 receptors in the hippocampus. This interference with memory-related brain processes makes it harder to encode, store, and retrieve new information while under the influence of cannabis. The severity and duration of these effects depend on dosage, frequency of use, and the user’s age and brain development stage.