Cannabis use has become increasingly common around the globe, particularly as legalisation has expanded. However, the growing perception of cannabis as a benign substance is far from the truth. Studies continue to shed light on the significant impact cannabis can have on brain function, with both short- and long-term consequences. Whether used recently or over a lifetime, cannabis use carries substantial risks, especially regarding cognitive health.
The Long-Term Effects of Heavy Cannabis Use on the Brain: A recent large-scale study examined young adults with varying levels of cannabis use, revealing troubling insights into the drug’s impact. Heavy lifetime cannabis use, defined as more than 1,000 uses, was found to significantly affect brain activity during cognitive tasks, particularly those requiring working memory. Specifically, users showed lower activation in critical regions such as the prefrontal cortex and anterior insula — areas essential for logic, decision-making, and memory retention.
These findings suggest that cannabis can fundamentally alter brain architecture. The results align with evidence showing cortical thinning and reduced receptor availability in regions affected by cannabis. Neural adaptation caused by exposure to tetrahydrocannabinol (THC), the main psychoactive compound in cannabis, likely underpins these changes, which may carry lasting impacts on cognitive abilities.
How Recent Cannabis Use Impairs Brain Function: For individuals who have recently consumed cannabis, brain activation during tasks requiring mental effort also declines. A key finding is that heavy users continued to display reduced working memory function even when they abstained from cannabis before testing, emphasising the drug’s lingering effects on brain health. Those who used cannabis recently also exhibited compromised brain function associated with social processing, hinting at deficits in understanding and responding to social cues effectively.
Cognitive Domains Most Affected by Cannabis: Research highlights that brain functions tied to working memory, logical reasoning, and language are the most severely impacted by cannabis use. These functions are critical for academic success, professional productivity, and maintaining healthy relationships. The diminished brain activation observed in these areas may contribute to poor decision-making, reduced problem-solving abilities, and an overall decline in cognitive performance.
Psychosocial Risks Tied to Cannabis Use: The study also links cannabis use with deficits in the theory of mind – the ability to empathise and understand others’ mental states. This, in part, explains cannabis’ association with heightened risks of developing mental health disorders, such as schizophrenia. Altered brain function in areas responsible for processing emotions and social cues could lead to impaired interpersonal relationships, social withdrawal, and the inability to maintain productive community involvement.
The Broader Implications for Health and Society: As cannabis products become more potent and accessible, the societal risks increase. Heavy and frequent cannabis use has already been related to higher rates of motor vehicle crashes, cardiovascular complications, and a rise in cannabis use disorder. The misconceptions surrounding the safety of cannabis are not only inaccurate but potentially harmful, leaving individuals vulnerable to long-lasting consequences.
This research underscores the fact that the negative outcomes of cannabis are neither short-term nor fleeting. Its impact on critical brain regions can persist over years, deeply affecting individuals and imposing broader public health burdens.
Final Thoughts: The evidence leaves no doubt – cannabis use poses serious risks to brain health and cognitive functioning. Heavy lifetime use significantly diminishes mental clarity, logical reasoning, and social comprehension, while recent use further exacerbates these effects. Despite efforts to normalise cannabis use, studies reveal a stark reality that must not be ignored. Educating communities on these risks is essential to addressing the growing prevalence of cannabis use and its damaging consequences.
Source: JAMA Network
