Compounding already serious issues, scientists have discovered a dangerous characteristic of marijuana smoking.

A new study by scientists indicates a link between cannabis use and a decrease in synaptic density in the brains of young individuals at risk of developing psychosis. Researchers from McGill University investigated how cannabis affects synaptic connections, which are essential for communication and brain development, and found that it exacerbates the existing deficit in synaptic connections among those at high risk for psychotic disorders, according to PsyPost.

The findings, published in the journal JAMA Psychiatry, contribute to the growing body of evidence regarding the biological connections between cannabis use and psychosis, suggesting new targets for potential treatment of such complications.

Psychotic disorders, such as schizophrenia, often emerge during adolescence or early adulthood—a critical period for brain maturation. Synaptic pruning, a natural process through which the brain refines its neural connections, plays a key role in this development. Disruptions in the pruning process are believed to contribute to the onset of psychosis; however, direct evidence is limited, mostly derived from postmortem or genetic studies.

In this study, the researchers utilized advanced imaging techniques to measure synaptic density in living individuals to understand how early psychosis intersects with cannabis use. The study involved 49 participants from Montreal, divided into three groups: individuals with a recent diagnosis of psychosis, those at high risk for psychosis, and healthy control subjects.

Using positron emission tomography (PET), researchers led by Mayra Belen Blasco, a psychiatrist and neurology graduate student, measured the level of SV2A, a protein marker of synaptic density, in brain regions associated with psychosis, such as the prefrontal cortex, hippocampus, and striatum. Magnetic resonance imaging (MRI) also assessed the microstructure of gray matter, providing additional insights into changes in the brain. Cannabis use was subjected to special analysis, with participants undergoing drug screening to evaluate its impact on synaptic density and psychotic symptoms.

The results revealed a reduction in synaptic density in the psychosis and high-risk groups compared to healthy individuals, particularly in areas critical for cognitive and emotional functioning, such as the anterior cingulate cortex and striatum. In the high-risk group, deficits were observed even before the onset of full psychotic symptoms, indicating early disruptions in brain connectivity.

Cannabis use exacerbated these deficits, especially in the striatum—a brain region associated with reward processing and motivation—highlighting its potential role in increasing the risk of developing such complications during critical periods of development. In addition to confirming the detrimental effects of cannabis, the study showed that reduced synaptic density is closely linked to negative symptoms of psychosis, such as social withdrawal and lack of motivation. These symptoms, which existing treatments struggle to address, may arise from disrupted neural connectivity.

However, the researchers found no significant correlation between synaptic density and "positive symptoms," such as hallucinations, suggesting that these symptom categories may be driven by different biological mechanisms. The researchers emphasized the importance of understanding the impact of cannabis on synaptic health and the timing of its effects on the brain development of young individuals.

While the study provides valuable insights, its authors acknowledge certain limitations. The small sample size, typical for PET studies due to their expense and complexity, reduces the generalizability of the findings. The cross-sectional design also limits conclusions about causal relationships—whether cannabis induces synaptic deficits or if individuals with vulnerabilities are more prone to its use.

Further research is needed, particularly longitudinal studies, to determine whether reducing cannabis consumption can mitigate these changes in the brain or even prevent the onset of psychosis. Nonetheless, important questions arise regarding why some individuals are more susceptible to its effects. Early interventions aimed at restoring synaptic health and individualized prevention strategies could significantly improve outcomes for those at risk.

This material is for informational purposes only and does not contain advice that may affect your health. If you are experiencing issues, consult a specialist.