Medical Bulletin 22/September/2025

Colon cancer is one of the most common cancers worldwide and starts as noncancerous polyps in the large intestine. While this study doesn’t prove that marathon running causes colon cancer, it does highlight a possible link that even very fit people should be mindful of regarding their colon health.

The study focused on healthy runners aged 35 to 50 who had completed many long-distance races. The researchers found that 41% of these runners had at least one adenoma, a type of colon polyp that can develop into cancer. More alarmingly, 15% had advanced adenomas, which are larger, more abnormal growths that are more likely to turn cancerous over time. These rates are much higher than the typical 1-2% expected in this age group.

Why might marathon running increase the risk? During long runs, blood flow is diverted from the gut to the muscles, reducing oxygen supply to the intestines and possibly causing small injuries. This repeated stress, along with inflammation, might lead to changes in the colon lining. Known symptoms like "runner’s colitis" or “runner’s trots” include loose stools and occasional bleeding, which might contribute to risk.

““This is the first prospective study exploring whether exercise-induced intestinal stress from long-distance running might raise cancer risk. While not proving cause, results suggest intense endurance exercise could increase colorectal cancer risk and warrant further research. This work may define a new at-risk group for earlier cancer screening. Young runners with blood in their stool after long runs—often dismissed as normal—should get screened, as early screening can prevent advanced cancers” said Dr. Cannon.

Reference: Tim Cannon, MD, Risk of pre-cancerous advanced adenomas of the colon in long distance runners; 2025 ASCO Annual Meeting; 2025 American Society of Clinical Oncology; Doi: 10.1200/JCO.2025.43.16_suppl.3619

Brain Rhythms Unlock How We Switch Between Old Memories and New Adventures: Study

Your brain is a master switchboard, constantly rewiring itself to balance memory and new experiences—a secret to human adaptability and survival. A recent international study published in PLoS Computational Biology reveals how the brain flexibly changes its communication routes based on context—whether recalling familiar memories or processing new information. The research sheds light on the brain’s dynamic balance between two inhibitory circuits that regulate slow (theta) and fast (gamma) rhythms.

The brain’s ability to recall memories or process new information relies on its flexible communication pathways. It shifts between different routes depending on whether we are experiencing something familiar or encountering something new. This flexible switching allows the brain to prioritize stored memories or fresh sensory inputs, helping us adapt and respond effectively to different situations.

To explore this, Researchers combined computational models with experimental recordings from the hippocampus of rats navigating familiar and new environments. They identified two communication modes: one prioritizes memory reactivation for known environments, while the other integrates memory with novel sensory inputs for new situations.

The study found that this flexible switching depends on the strength and balance of synaptic connections controlling feedforward and feedback inhibition in neural circuits. These findings overturn prior beliefs that slow brain rhythms merely organize fast activity; instead, the relationship is bidirectional. This intricate dance allows the brain to prioritize inputs from either stored memories or fresh sensory data, adapting in real time to cognitive demands.

Beyond memory, the researchers suggest this balance may also play a role in attention and other cognitive functions. The findings could inform new therapies for neurological disorders like epilepsy and Alzheimer’s disease by targeting disrupted brain rhythms.

Reference: Dimitrios Chalkiadakis, Jaime Sánchez-Claros, Víctor J. López-Madrona, Santiago Canals, Claudio R. Mirasso. The role of feedforward and feedback inhibition in modulating theta-gamma cross-frequency interactions in neural circuits. PLOS Computational Biology, 2025; 21 (8): e1013363 DOI: 10.1371/journal.pcbi.1013363

Severe Pregnancy Sickness Linked to Over 50% Higher Mental Health Risks

Imagine a world where nausea during pregnancy goes beyond mere discomfort—this is the harsh reality for women with hyperemesis gravidarum (HG), a severe condition affecting nearly 3.6% of pregnancies globally.

The largest study on pregnant women with excessive nausea and vomiting (hyperemesis gravidarum), and published in the journal Nature, has identified increased risks of numerous neuropsychiatric and mental health outcomes.

Hyperemesis gravidarum (HG) is not just typical morning sickness; it’s a severe condition marked by relentless nausea, vomiting, dehydration, and weight loss of over 5% of pre-pregnancy weight. This often leads to extended hospital stays during the first trimester, where women require intravenous fluids and medications to manage symptoms. The constant vomiting can cause electrolyte imbalances, malnutrition, and even serious complications like Wernicke encephalopathy, a neurological disorder from thiamine deficiency. Beyond the physical challenges, this intense illness significantly affects mental well-being, making comprehensive, compassionate care essential for both mother and baby.

The largest international study to date, involved over 476,000 women, and revealed alarming links between HG and a variety of serious mental health conditions. Women with HG face significantly increased risks of anxiety, depression, postpartum psychosis, eating disorders, and even severe neurological disorders like Wernicke’s encephalopathy. Postpartum depression risk is nearly tripled, with many women experiencing challenges far beyond the physical symptoms.

Interestingly, the severity of physical symptoms does not always correlate with mental health impact. Women with milder physical cases often suffer profound psychological distress, highlighting a critical gap in care. Experts like Dr. Hamilton Morrin from King’s College London stress the urgent need for integrated physical and mental health support for these women.

This groundbreaking research sheds light on the invisible mental health burden of HG, urging healthcare providers to recognize and address these challenges early. A holistic approach to treatment is essential to protect the well-being of mothers and their babies, ensuring both physical health and emotional resilience throughout pregnancy and beyond.

Reference: Fejzo, M., Rocha, N., Cimino, I. et al. GDF15 linked to maternal risk of nausea and vomiting during pregnancy. Nature 625, 760–767 (2024). https://doi.org/10.1038/s41586-023-06921-9