DATE: August 15, 2025 at 08:00AM
SOURCE: PSYPOST.ORG

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TITLE: Common infections during pregnancy unlikely to impact children’s intelligence, large study finds

URL: https://www.psypost.org/common-infections-during-pregnancy-unlikely-to-impact-childrens-intelligence-large-study-finds/

New research published in PLOS Medicine based on nationwide data from Denmark suggests that common maternal infections during pregnancy are unlikely to have a meaningful effect on children’s cognitive outcomes later in life. In one of the largest studies of its kind, researchers analyzed school grades and intelligence scores among more than 250,000 siblings and found no consistent differences based on whether their mothers had been prescribed antibiotics or hospitalized for infection during pregnancy.

While certain severe infections during pregnancy—such as rubella or toxoplasmosis—are known to pose risks to fetal brain development, the broader implications of more common infections, like urinary tract or respiratory infections, have remained unclear. Some previous studies have suggested these everyday illnesses might influence the child’s future cognitive performance. However, many of these earlier studies were unable to fully account for shared family factors that might bias the results, such as parental intelligence, socioeconomic status, or genetic predispositions.

“Previous studies and anecdotal clinical stories have suggested an negative impact of common maternal infections on offspring cognitive outcomes. However, most previous studies have been small and have not been able to correct for the social biases associated with both the risk of maternal infection during pregnancy and the cognitive outcome of the offspring,” said study author Anders Husby, a resident physician and postdoctoral researcher at the Department of Paediatrics and Adolescent Medicine at Rigshospitalet, and the Department of Congenital Disorders at Statens Serum Institut in Copenhagen.

“Using data from our previous study on gestational age at birth and long-term cognitive outcome, we could investigate the association between common maternal infections during pregnancy and long-term cognitive outcome in a very large nationwide cohort composed of full-siblings. Using the full-sibling design, we could compare siblings where the same mother, who had or hadn’t an infection during pregnancy, and thereby minimize confounding from social factors.

The data for the research came from multiple national Danish registries. The researchers included information on filled antimicrobial prescriptions as a proxy for mild infections and inpatient hospitalizations to represent more severe cases. They then linked these exposure records to standardized school grades in language and mathematics at age 15–16, as well as intelligence test scores from mandatory military conscription assessments taken by adolescent boys.

The cohort included over 274,000 children born between 1996 and 2003, with nearly 81,000 having mothers who had filled at least one prescription for a systemic antimicrobial during pregnancy. A smaller subset—roughly 5,600 children—had mothers who were hospitalized for infections while pregnant. Intelligence scores were available for a sub-cohort of full brothers who had undergone testing for military service.

The results indicated little to no difference in academic or cognitive performance based on maternal infection exposure. For example, among children whose mothers filled one prescription for antibiotics during pregnancy, the average difference in language or math grades was virtually zero once shared family factors were accounted for. Similarly, the estimated IQ difference in adolescent males was only about 0.3 points on average—well within the margin of error.

In contrast, when the researchers looked at models that did not account for shared family factors, they found consistent and statistically significant associations between maternal infections and lower scores. This discrepancy highlights how results may be influenced by family-level confounding, and it underscores the value of sibling-based analyses in addressing such biases.

Even when examining different types of antibiotics or timing of exposure across pregnancy, the results did not point to any consistent effects. The most common antibiotics—such as beta-lactams—showed no meaningful associations with lower academic performance or IQ. Nor did the timing of exposure appear to matter: infections occurring during early gestation, late gestation, or any specific bi-weekly window were not linked to worse outcomes.

“We were open as to whether the exposure (i.e., common maternal infections) had negative or no effects on cognitive outcomes, so we were not surprised by the results,” Husby told PsyPost. “However, it is reassuring to see that our study with large certainty can rule out moderate-or-large negative effects on cognitive outcomes from common maternal infections.”

There were a few small exceptions. For example, there was a slight reduction in mathematics scores among children whose mothers had filled one or two antibiotic prescriptions. But these differences were minimal—about 1–2% of a standard deviation—and the researchers noted that confidence intervals ruled out anything larger than a 3% drop. These findings, they argue, are not likely to be meaningful at the individual or population level.

The study also explored whether more severe infections, indicated by hospitalization, might have a stronger effect. One notable finding was a slight dip in school grades among children whose mothers had been hospitalized for an infection during weeks 24–25 of pregnancy. But this effect disappeared when the analysis was limited to children born at full term, suggesting that the initial association may have been influenced by gestational age rather than the infection itself.

The researchers conducted several sensitivity analyses to test the robustness of their findings. These included restricting the sample to term births, adjusting for maternal smoking, and imputing scores for children who did not participate in school exams. Across these variations, the results remained consistent: there was no evidence of meaningful cognitive harm associated with common infections during pregnancy.

“Our study suggests that common maternal infections and the associated antimicrobial treatment during pregnancy are unlikely to meaningfully impair offspring cognitive outcomes, such as school grades or adolescent IQ,” Husby said. “This provides reassuring evidence supporting the safety of commonly prescribed antimicrobials during gestation, and suggest an minor role of common prenatal infections in cognitive deficits in offspring.”

The study does have limitations. One is that it lacked information on medications administered during hospital stays, which could potentially affect outcomes. However, hospitalization for infection was relatively rare, and the analysis of this group did not show signs of negative cognitive effects. Another limitation is that the researchers could not identify specific pathogens responsible for infections, nor could they account for maternal fever, which is often part of the body’s inflammatory response.

“We hope in future studies to could look a specific infections, which was not possible in the current study which only identified infections by antibiotics prescriptions and diagnostic codes for infectious disease hospitalization,” Husby said.

Still, the absence of dose-response patterns or consistent links between more severe exposure and worse outcomes suggests that any such factors may have minimal impact on cognition.

However, the authors also caution that while their findings apply to common infections and antibiotic use, they do not rule out the well-established effects of rare but serious prenatal infections. Serious diseases can still cause profound developmental disabilities, and preventive measures remain essential for managing those risks.

“Our findings are mainly applicable to common maternal infections identified by maternal antibiotic prescriptions and common hospitalizations for infections, as it was were we had most statistical power to indicate a difference. Furthermore, it is well-documented that certain rare prenatal infection (e.g. rubella, malaria, and toxoplasmosis) can lead to severe cognitive deficits in the fetus.”

In addition to reassuring expectant parents, the study carries broader methodological implications. The researchers noted that earlier studies had hinted at negative outcomes associated with prenatal infection, but these associations often disappeared when sibling comparisons were used. This suggests that family-level confounding may play a larger role than previously thought in shaping observed outcomes.

“Initially, it looked as if infections might be linked to lower school grades and IQ,” Husby explained. “But when we compared within sibling-groups (where one sibling was exposed to maternal infection in the womb and others wasn’t), those differences disappeared. That is a powerful reminder of how critical it is to use study designs that can robustly address the impact of social biases.”

The study, “Maternal infections during pregnancy and offspring cognitive outcome: A nationwide full-sibling cohort study,” was authored by Anders Husby, Kim D. Jakobsen, Jan Wohlfahrt, and Mads Melbye.

URL: https://www.psypost.org/common-infections-during-pregnancy-unlikely-to-impact-childrens-intelligence-large-study-finds/

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DATE: August 15, 2025 at 06:00AM
SOURCE: PSYPOST.ORG

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TITLE: Scientists uncover brain’s “reset button” for splitting memories into distinct events

URL: https://www.psypost.org/scientists-uncover-brains-reset-button-for-splitting-memories-into-distinct-events/

New findings published in the journal Neuron suggest that the locus coeruleus—a tiny region buried deep in the brainstem—may play a key role in helping the brain separate one memory from the next. This cluster of neurons, long known for its role in arousal and attention, appears to become especially active when meaningful changes occur, such as a shift in context or environment. That activity seems to serve as a kind of neural punctuation mark, telling the brain where one event ends and another begins.

The study, led by researchers at UCLA and Columbia University, used a combination of functional brain imaging and pupil tracking to monitor moment-by-moment changes in brain activity as people encoded and later recalled sequences of information. The results indicate that bursts of activity in the locus coeruleus tend to signal important transitions and promote the creation of distinct memory representations—possibly by “resetting” memory circuits in the hippocampus.

“Life unfolds continuously, but to make sense of it, our brains naturally break it up into meaningful events. We do not remember the past as one long stream. Instead, we recall it as distinct chapters that shape our personal stories and understanding of the world. We wanted to determine how our brains accomplish this remarkable feat,” said study author David Clewett, an assistant professor at UCLA.

Earlier research has pointed to the hippocampus as a critical player in episodic memory. This brain region is thought to support both the integration of events that occur close together in time and the separation of those that differ in context. Yet scientists have questioned what signals the hippocampus to shift between these two modes. The team behind the new study proposed that the locus coeruleus might be the trigger.

This small nucleus, which releases the neurotransmitter norepinephrine, is known to help the brain respond to novelty and unexpected changes. It also has strong connections to memory-related regions such as the dentate gyrus—a subregion of the hippocampus involved in distinguishing between similar experiences. The authors theorized that phasic bursts of locus coeruleus activity might act as a “reset” signal that prompts the hippocampus to update its memory representations when significant changes are detected.

The researchers recruited 36 healthy young adults to participate in a memory task while undergoing brain scanning. After data exclusions due to technical issues or participant attrition, 32 individuals were included in the final analysis. Of these, 28 had valid eye-tracking data.

While lying in an MRI scanner, participants viewed series of neutral object images. Before each image, they heard a tone in either their left or right ear, which indicated which hand they should use to make a size judgment about the object. The tones were used not just for task instructions, but also to manipulate perceived context. Each sequence was organized into four blocks of eight images. Within each block, the same tone repeated in the same ear, creating a sense of continuity. At transition points, the tone changed in both pitch and ear—producing a perceptual event boundary.

After each sequence, participants completed memory tests outside the scanner that asked them to judge the order and temporal distance between pairs of items. The researchers also collected high-resolution brain scans to locate the locus coeruleus in each participant, and they used neuromelanin-sensitive imaging to estimate long-term activity levels in the region. Additionally, eye-tracking data were used to measure changes in pupil size, a known proxy for arousal and locus coeruleus activation.

The behavioral results showed that participants had more difficulty remembering the order of items that spanned an event boundary than items that occurred within the same context. This suggests that boundaries introduced by tone switches effectively segmented the experience into separate memories. At the same time, participants were slower to respond to objects that followed a boundary, which may indicate increased attention to contextual change.

Importantly, bursts of activation in the locus coeruleus during these boundaries were linked to reduced memory for the temporal order of item pairs—an indicator that the brain was separating rather than integrating those events. This trial-by-trial relationship between locus coeruleus activity and memory separation did not appear during stable stretches of the sequence.

“We were surprised that transitions between events, known as ‘event boundaries,’ didn’t always activate the locus coeruleus (LC), a core hub of the brain’s arousal system,” Clewett told PsyPost. “Even so, this pattern revealed something important: when the LC did respond, memories became separated. This suggests that only certain cues or level of engagement may be important for structuring new memories.”

To examine the effects on memory circuits more directly, the researchers looked at activation patterns in hippocampal subfields. They found that items separated by an event boundary were associated with reduced pattern similarity in the left dentate gyrus—indicating that the hippocampus encoded them as more distinct events. This pattern separation effect was more pronounced when locus coeruleus activation at the boundary was stronger. By contrast, another hippocampal subregion, CA2/3, showed the opposite trend, with increased pattern similarity during boundaries, although the meaning of this effect remains less clear.

The link between pupil dilation and brain activity also aligned with the hypothesis. Tones marking boundaries elicited larger changes in pupil size compared to repeated tones, and those dilations tracked with locus coeruleus activation.

Specific components of the pupil response predicted memory performance and attention to boundaries. Participants who showed stronger early pupil responses to boundary tones also had worse temporal order memory across those boundaries, supporting the idea that enhanced local processing comes at the expense of integrating events over time.

Beyond these phasic effects, the researchers explored what might happen when the locus coeruleus is in a heightened state of chronic activation. Using neuromelanin imaging, they found that individuals with higher structural signal intensity in the locus coeruleus—thought to reflect sustained norepinephrine output—showed weaker pupil responses to boundaries. This suggests that under conditions of hyperarousal, the system becomes less sensitive to meaningful changes, potentially impairing the segmentation process that supports memory organization.

Functional MRI analyses reinforced this idea. Participants with greater low-frequency fluctuations in locus coeruleus activity, a proposed marker of background activation, showed reduced responses to boundaries both in terms of pupil dilation and phasic neural activation. In other words, when the “alarm system” of the brain is always on, it may fail to ring when it matters most.

“Our key takeaways were that arousal processes, the brain’s alertness system, help us detect important changes and use those moments to organize information into distinct memories,” Clewett explained. “However, individuals who experience chronically elevated stress may fail to register these changes, making it harder to perceive and remember discrete events. This insight opens the door to new interventions that could target hyperarousal in conditions like PTSD or Alzheimer’s disease to help improve how memories are formed and remembered.”

The study offers compelling evidence for the role of the locus coeruleus in segmenting memory, but the findings are correlational. The researchers cannot definitively conclude that locus coeruleus activity causes the observed memory effects. They also note the technical challenges of imaging such a small and deeply located brain structure, although they took several steps to ensure accuracy.

“One of the biggest caveats is that the LC is tiny and difficult to image in humans,” Clewett noted. “While we cross-validated LC activation using both pupillometry and structural imaging, fMRI signals from this region are still noisy and should be interpreted with caution. Additionally, the limited spatial resolution of our fMRI scans makes it challenging to fully segment the hippocampus into its distinct subregions.”

“Future work could use techniques with higher spatial and temporal resolution to image these brain regions. It would also be helpful to manipulate arousal states more directly to determine the causal influence of the LC on memory structuring.”

Another open question concerns the relationship between stress, tonic locus coeruleus activation, and memory. The current findings suggest that chronic hyperarousal can blunt memory segmentation, but further research is needed to explore how interventions that regulate arousal—such as mindfulness, breathing exercises, or pharmacological treatments—might restore normal memory function in people experiencing stress-related disorders.

“Ultimately, our goal is to design behavioral or neuromodulatory interventions that help ‘quiet’ elevated LC activity and reduce hyperarousal in conditions like Alzheimer’s disease and PTSD,” Clewett said. “We are also interested in exploring whether these approaches can complement memory-based therapies aimed at improving how people perceive and remember events.”

The study, “Locus coeruleus activation ‘resets’ hippocampal event representations and separates adjacent memories,” was authored by David Clewett, Ringo Huang, and Lila Davachi

URL: https://www.psypost.org/scientists-uncover-brains-reset-button-for-splitting-memories-into-distinct-events/

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DATE: August 14, 2025 at 04:00PM
SOURCE: PSYPOST.ORG

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TITLE: Lumberjack amputates ears and penis during psychotic episode linked to cannabis and kratom use

URL: https://www.psypost.org/lumberjack-amputates-ears-and-penis-during-psychotic-episode-linked-to-cannabis-and-kratom-use/

A new case report published in Frontiers in Psychiatry describes the harrowing experience of a 31-year-old man in the Czech Republic who amputated both ears and his penis during a psychotic episode. The incident occurred after he consumed a combination of psychoactive substances, including cannabis and kratom. The man survived, underwent reconstructive surgery, and later remained abstinent while continuing psychiatric treatment. His case highlights how psychoactive drug use may contribute to rare but extreme self-harm behaviors during psychosis.

Psychosis refers to a mental state in which an individual loses contact with reality. This can involve hallucinations—perceiving things that are not there—or delusions, which are strongly held false beliefs. During psychotic episodes, people may misinterpret their surroundings, feel paranoid, or experience disorganized thinking. Psychosis can occur as part of schizophrenia or bipolar disorder but can also be brought on by substance use, brain injury, or extreme stress.

The patient was a physically healthy man working as a lumberjack. He was admitted to the hospital after severely injuring himself in freezing outdoor temperatures. He had amputated both ears and his penis, inflicted deep cuts on his arms, and sustained frostbite on his feet. Medical personnel found him agitated and paranoid, but he was alert and responsive. Emergency surgery stabilized his condition.

Toxicological tests detected cannabinoids, mitragynine, and 7-hydroxymitragynine—substances found in kratom, a plant increasingly used as a stimulant or pain reliever. The man had a history of drug use dating back to adolescence, including regular cannabis consumption and occasional use of alcohol, methamphetamine, and hallucinogens such as psilocybin mushrooms. He also reported frequent substance combinations, sometimes leading to memory blackouts.

Notably, he had a previous episode in 2018 involving aggression and self-harm after using multiple substances. At that time, psychotic symptoms disappeared once the intoxication resolved, and he was discharged without a long-term psychiatric diagnosis. However, he did not pursue ongoing psychiatric or substance use treatment.

After the 2024 incident, psychological testing suggested below-average intellectual function, poor emotional control, and impaired social judgment. Clinicians found no signs of a chronic psychotic disorder like schizophrenia but diagnosed him with substance-induced psychosis. He lacked insight into his mental state and showed little emotional reaction to the severity of his injuries.

Over the course of his hospital stay, antipsychotic and sedative medications helped stabilize his condition. While he initially refused addiction treatment, he later became engaged with psychiatric care. His desire for reconstructive penile surgery became a motivating factor in his recovery. Five months after the incident, he underwent successful reconstruction and remained abstinent from drugs and alcohol. He also continued outpatient psychiatric follow-ups and appeared free of psychotic symptoms.

Case reports provide detailed accounts of unusual or informative clinical scenarios. While they are helpful for identifying possible links between substance use and mental health crises, they do not prove causation. A single case cannot tell us how often such outcomes occur or whether similar cases would follow the same trajectory. There may also be missing details, such as unconfirmed drug doses or incomplete psychiatric histories.

Despite these limitations, case reports are often the first signal that a particular substance or behavior may be linked to rare or extreme health outcomes. In this case, the unusual combination of self-mutilation, substance use, and psychosis raises concerns about how cannabis and kratom may interact to influence mental health.

Both cannabis and kratom are widely used psychoactive substances, but each carries potential risks, particularly for individuals with mental health vulnerabilities.

Cannabis has long been associated with the onset of psychotic symptoms in some individuals. High doses of tetrahydrocannabinol (THC), its main psychoactive compound, can alter dopamine signaling in the brain, which plays a key role in reward and perception. Some people may develop paranoia, hallucinations, or delusions, especially if they have a genetic predisposition or underlying mental health issues. While most cannabis-induced psychosis is short-lived, it may signal a greater risk for later development of schizophrenia-like disorders.

Kratom is a plant native to Southeast Asia that has gained popularity in the U.S. as an herbal supplement for pain, anxiety, or opioid withdrawal. Its primary alkaloids, mitragynine and 7-hydroxymitragynine, affect opioid and other brain receptors, producing stimulant effects at low doses and sedative, opioid-like effects at higher doses. In rare cases, kratom use has been linked to psychiatric symptoms, including hallucinations, mania, or psychosis. Because its metabolites are not detected in standard toxicology screens, its role in mental health crises may be underrecognized.

In the reported case, both cannabis and kratom were detected, but the exact contributions of each substance to the patient’s psychosis remain unclear. Still, their combined effects may have lowered the patient’s threshold for psychosis, particularly in the context of past substance-induced episodes and ongoing psychological vulnerabilities.

While self-amputation of body parts is an extreme and rare consequence of psychosis, this case is not unique. Other reports have documented similar injuries in the context of drug-induced or primary psychotic disorders. What makes this case notable is the involvement of kratom—a substance often marketed as safe and natural—and the severe physical and psychological consequences that followed.

The patient’s story also suggests that motivation, particularly a concrete goal like reconstructive surgery or regaining a driver’s license, can support engagement in treatment and recovery. Despite refusing formal addiction services, he remained abstinent and continued psychiatric care during follow-up.

The case report, “Cannabis and kratom-induced self-amputation of ears and penis,” was authored by Marek Broul, Xenia Rudenko, Adam Bajus, Jiří Král, Dan Mwemena Kyenge, Zdenka Staňková, and Jakub Albrecht.

URL: https://www.psypost.org/lumberjack-amputates-ears-and-penis-during-psychotic-episode-linked-to-cannabis-and-kratom-use/

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