Selenium is an essential micronutrient that the human body incorporates into a family of proteins known as selenoproteins. These proteins perform a remarkable range of biochemical duties, including antioxidant defense, thyroid hormone metabolism, and immune regulation. The brain is particularly dependent on this system because neural tissue consumes a disproportionate share of the body’s oxygen and generates a steady stream of reactive oxygen species as a byproduct of its relentless metabolic activity. When selenium is scarce, the antioxidant capacity of developing neurons may be compromised at precisely the moment when the brain is wiring itself at its most furious pace. Deficiency has also been linked in animal studies to alterations in neurotransmitter systems, including dopaminergic and serotonergic pathways, which are central to attention regulation and impulse control. This biological plausibility is what motivated the research team to ask whether a mother’s selenium status during pregnancy leaves a measurable trace in her child’s behavior years later.

The study drew on a well-established cohort in Bhaktapur, a city in the Kathmandu Valley where the research group has conducted nutrition studies for more than a decade. In total, 720 mother-infant dyads were enrolled, and maternal plasma selenium concentrations were measured in blood samples taken early in pregnancy. This timing matters. The first trimester and early second trimester are periods of rapid neural tube formation, neuronal proliferation, and the beginnings of synaptic architecture, so any nutritional insult during this window could theoretically have outsized consequences. The researchers then waited, quite literally, for the children to grow. When the children reached four years of age, their mental health was assessed using a parent-reported questionnaire called the Strengths and Difficulties Questionnaire, or SDQ, in its Nepalese version.

The SDQ is one of the most widely used brief behavioral screening instruments in the world. It asks parents to rate their child on a series of attributes that cluster into five subscales: emotional symptoms, conduct problems, hyperactivity-inattention, peer relationship problems, and prosocial behavior. Because the questionnaire had not previously been validated in this specific Nepalese preschool population, the team took the methodologically important step of testing whether the original five-factor structure actually held up in their data. Using confirmatory factor analysis, a statistical technique that evaluates how well observed responses map onto hypothesized underlying dimensions, they found that the five-factor model fit the data well after some modifications. The comparative fit index reached 0.967, comfortably above conventional thresholds, while the root mean square error of approximation was 0.059, indicating acceptable approximation error. In practical terms, this means the Nepalese version of the parent-rated SDQ can be considered a psychometrically sound tool for assessing preschool mental health in this setting, a contribution that will benefit future research in the region regardless of what the selenium analysis showed.

The average maternal plasma selenium concentration in the cohort was 74.7 micrograms per liter, with a standard deviation of 10.2 micrograms per liter. This figure sits in an interesting zone. It is not low enough to constitute overt deficiency by most clinical standards, but it is well below the concentrations typically observed in selenium-replete populations in North America and parts of Europe, where means can exceed 100 micrograms per liter. Nepal’s soil is known to be variable in selenium content, and the predominantly cereal-based local diet does not necessarily compensate for that variability. The researchers therefore had genuine reason to suspect that a meaningful fraction of the pregnant women in the cohort might be experiencing suboptimal selenium status during a critical developmental window.

To analyze the relationship between prenatal selenium and child behavior, the team used generalized linear models, examining maternal plasma selenium both as a continuous variable and in categorized forms, including tertiles that divided the sample into thirds of exposure. The children’s SDQ subscale scores served as the outcomes. The headline finding emerged from the tertile analysis: children whose mothers fell in the lowest selenium tertile during pregnancy had significantly higher hyperactivity-inattention scores at age four than children whose mothers were in the middle tertile. The adjusted regression coefficient was 0.329, with a 95 percent confidence interval running from 0.023 to 0.636, meaning the difference was statistically significant but modest in magnitude, and the confidence interval only narrowly excluded the null value of zero.

Crucially, however, the pattern did not behave the way a classic dose-response relationship would. If selenium deficiency were driving hyperactive behavior in a straightforward manner, one might expect the lowest tertile to differ from the middle tertile, and the middle tertile to differ from the highest, producing a graded gradient across the exposure distribution. Instead, the association appeared only when the lowest and middle tertiles were compared, and no corresponding difference emerged between the middle and highest groups. The analysis of selenium as a continuous variable likewise did not yield significant associations. The authors are appropriately cautious on this point, describing their evidence as limited and noting that the isolated finding lacks the clear exposure-response pattern that would strengthen a causal interpretation. It is possible that a threshold effect exists, in which only selenium status below a certain level matters, but it is equally possible that the result reflects chance, residual confounding, or the many comparisons inherent in examining multiple subscales across multiple exposure parameterizations.

Several other limitations deserve attention. The SDQ was completed by parents, which introduces the possibility of reporting bias, although the validation work strengthens confidence that the instrument measures coherent behavioral dimensions in this population. Plasma selenium reflects relatively recent intake and is influenced by the proteins that transport the element, notably selenoprotein P, so a single early-pregnancy measurement may not perfectly capture selenium status across the full gestational period. The Bhaktapur cohort, while valuable, is drawn from one urbanizing South Asian community, and its selenium distribution differs from that of populations where deficiency is rare, which limits generalizability in both directions. Confounding by overall nutritional quality is also a real concern, since women with low selenium may differ in other dietary and socioeconomic respects that independently influence child development, even though the models adjusted for available covariates.

Still, the study’s strengths are considerable. The prospective design, in which exposure was measured in pregnancy and outcome years later, removes much of the reverse-causation ambiguity that plagues cross-sectional nutrition research. The sample size of 720 dyads is respectable for a birth cohort study of this kind, and the dual contribution of a validated behavioral instrument and a novel exposure-outcome analysis makes the paper useful on two fronts. For selenium biology, the findings add a tentative data point to a small but growing literature linking maternal micronutrient status to child neurobehavioral outcomes, a field that has historically focused more heavily on iron, iodine, and folate. For public health in South Asia, the results raise the possibility that selenium, a mineral rarely included in prenatal supplementation programs, deserves closer scrutiny. The authors themselves conclude that confirmation in further studies is required, and that is the right note: one modest association, in one cohort, at one age, is a signal worth chasing rather than a conclusion worth announcing. Future work with repeated selenium measurements, biomarkers of selenium-dependent enzyme activity, and follow-up into school age will be needed to determine whether the trace element truly shapes the developing mind, or whether this finding dissolves under the weight of replication.

Subject of Research: The association between prenatal maternal selenium concentration and mental health outcomes in four-year-old children in a Nepalese mother-child cohort study.

Article Title: The association between prenatal maternal selenium concentration and mental health in early childhood, a mother-child cohort study

Article References: Ranjitkar, S., Kvestad, I., Chandyo, R. K., Bakken, K. S., Ulak, M., Strand, T. A., Huber, S., Averina, M., & Hysing, M. (2026). The association between prenatal maternal selenium concentration and mental health in early childhood, a mother-child cohort study. PLOS One, 21(10), e0360527. https://doi.org/10.1371/journal.pone.0360527

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0360527

Keywords: selenium, prenatal nutrition, child mental health, hyperactivity, inattention, Nepal, birth cohort, Strengths and Difficulties Questionnaire, micronutrients, neurodevelopment, pregnancy, PLOS One