Summary: While antibiotics are lifesaving tools, their impact may extend beyond fighting infection to affecting maternal mental health. A massive nationwide study has identified a “stepwise” link between antibiotic use and psychological distress in pregnant women.
Analyzing data from over 94,000 participants in the Japan Environment and Children’s Study (JECS), researchers found that women who used antibiotics both before and during early pregnancy were significantly more likely to experience severe psychological distress.
The culprit? Likely the gut-brain axis, where antibiotics disrupt the microbiota that help regulate mood.
Key Facts
- The Dose-Response Connection: The more periods a woman used antibiotics (pre-conception and early pregnancy), the higher her odds of mental health struggles.
- Severe Distress Risk: Women using antibiotics in both time periods saw a 50% increase in the odds of severe psychological distress (K6 score >13) compared to those who used none.
- The Microbiome Factor: Researchers suggest that because antibiotics wipe out beneficial gut bacteria, they may trigger inflammation or chemical imbalances that lead to anxiety and depression.
- Massive Dataset: The study is one of the largest of its kind, adjusting for variables like age, income, smoking, and previous psychiatric history to ensure the antibiotic link remained clear.
Source: University of Toyama
Perinatal depression, which occurs during pregnancy or in the period after childbirth, is one of the most common mental health conditions experienced by women. The condition affects the well-being of the mother during both pregnancy and after childbirth, as well as the development of the child.
Multiple factors influence maternal mental health and recently, emerging evidence suggests an association between antibiotic use and maternal mental health.
The study published in Volume 26 of the journal BMC Public Health on January 10, 2026, was conducted by Collaborative Researcher Kenta Matsumura, formerly a Junior Associate Professor at the Department of Public Health, University of Toyama, Japan, and currently a Professor at Aomori University of Health and Welfare, Japan, along with Dr. Hidekuni Inadera at the Toyama Unit Center of the Japan Environment and Children’s Study (JECS), University of Toyama.
“While there are situations in which antibiotics are essential, the emergence of antibiotic-resistant bacteria due to the inappropriate use of antibiotics has become a significant concern. We wanted to understand how antibiotic use is associated with psychological distress among pregnant women,” shares Prof. Matsumura, as the inspiration behind the study.
To examine the relation between antibiotic use and psychological distress, the researchers analyzed data from 94,490 pregnant women enrolled in JECS, an ongoing nationwide birth cohort study designed to investigate how environmental factors are associated with children’s health and development.
Most women enrolled in the study were at around 12 weeks of pregnancy, and follow-up assessments were conducted when they were about 15 weeks pregnant.
Information on the participant’s antibiotic use was collected for the year before early pregnancy. This period covered two stages: from before conception until pregnancy recognition, and from pregnancy recognition until enrollment in the study. Participants were then categorized into three groups: those who did not use antibiotics, those who used antibiotics during either one of the two periods, and those who used antibiotics during both periods.
The researchers evaluated participants’ psychological distress using the Japanese version of the Kessler Psychological Distress Scale (K6), a six-item self-reported questionnaire in which participants answer six questions about their mental state.
The researchers then used the group that did not take antibiotics as the reference group to estimate the association between antibiotic use and psychological distress in the other two groups. They calculated adjusted odds ratio, a statistical measure used to estimate the strength of an association between two variables, in this case, antibiotic use and psychological distress.
“We found that antibiotic use before and during pregnancy was associated with psychological distress in early- to mid-pregnancy, and that this association showed a stepwise pattern in a nationwide dataset of approximately 94,000 participants,” says Prof. Matsumura.
After accounting for potential factors that could influence both antibiotic use and psychological distress, such as maternal age, pre-pregnancy body mass index, education level, income, smoking status, alcohol use, marital status, and psychiatric history, the analysis showed that compared with no antibiotic use, the adjusted odds ratios for moderate psychological distress (K6 score of 5 to 12) were 1.12 for use during either period and 1.22 for use during both periods. For severe psychological distress (K6 score greater than 13), the adjusted odds ratios were 1.07 and 1.50, respectively.
The higher odds ratios observed with greater antibiotic exposure suggest that the likelihood of psychological distress during early- to mid-pregnancy was higher among participants who reported antibiotic use during more periods.
One possible explanation for these findings involves the gut microbiota, which can be altered by antibiotics. Changes in gut microbiota have been observed in various conditions, including obesity, diabetes, and inflammation, and such changes have also been examined in relation to psychiatric conditions.
The researchers emphasize that these findings do not suggest avoiding antibiotics when they are medically necessary. Instead, the findings may contribute to ongoing discussions about appropriate antibiotic use and efforts to reduce unnecessary prescriptions.
“This study may encourage women who are planning pregnancy or in early pregnancy to become more aware of the appropriate use of antibiotics. Antibiotics are essential when medically necessary; however, increasing awareness about avoiding unnecessary prescriptions—such as for common colds—may also be relevant from a maternal mental health perspective,” concludes Prof. Matsumura.
Funding information
The JECS was funded by the Ministry of the Environment, Japan.
Key Questions Answered:
A: No. Professor Matsumura emphasizes that antibiotics are essential when medically necessary for infections. The concern is “inappropriate use”—such as taking them for a common cold (which is viral). The goal is to reduce unnecessary prescriptions that could unnecessarily disrupt your gut health.
A: It’s all about the gut-brain axis. Your gut bacteria produce many of the chemicals (like serotonin) that regulate your mood. When antibiotics clear out an infection, they also clear out these “good” bacteria, which can send distress signals to your brain, potentially leading to the symptoms of depression or anxiety.
A: The study focused on early-to-mid pregnancy. While the gut microbiome can recover, the “stepwise” increase in distress suggests that the timing of the disruption—right when the body is undergoing massive hormonal shifts—is particularly sensitive.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this pregnancy and mental health research news
Author: Yumiko Kato
Source: University of Toyama
Contact: Yumiko Kato – University of Toyama
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Periconceptional antibiotic use and early- to mid-pregnancy psychological distress in a nationwide birth cohort: cross-sectional analysis from the Japan Environment and Children’s Study” by Kenta Matsumura, Hitomi Inano, Junko Sakai, Kanako Shimada, Akiko Tsuchida, Hidekuni Inadera & the Japan Environment and Children’s Study (JECS) Group. BMC Public Health
DOI:10.1186/s12889-025-26119-0
Abstract
Periconceptional antibiotic use and early- to mid-pregnancy psychological distress in a nationwide birth cohort: cross-sectional analysis from the Japan Environment and Children’s Study
Background
Antibiotic use has recently emerged as a potential risk factor for psychiatric disorders, but evidence regarding its risk during pregnancy remains limited, despite the frequent use of antibiotics in pregnant women. We investigated the association between antibiotic use in the year prior to early pregnancy and psychological distress during early- to mid-pregnancy.
Methods
Participants were 94,490 expectant mothers from the Japan Environment and Children’s Study, an ongoing nationwide birth cohort study. Antibiotic use during the year before early pregnancy was categorized as follows: (1) no use, (2) use during either the period before or after pregnancy recognition, and (3) use during both periods. Psychological distress was measured during early- to mid-pregnancy using the Kessler Psychological Distress Scale, with scores of 5–12 and ≥ 13 indicating moderate and severe psychological distress, respectively. A Bayesian multinomial generalized linear model was used to calculate adjusted odds ratios (aORs) and 95% credible intervals (95% CrIs), controlling for a priori selected potential confounders.
Results
Analysis using no antibiotic use as a reference revealed that the aORs (95% CrIs) for moderate psychological distress were 1.07 (0.97–1.19) for use during either period and 1.22 (1.08–1.38) for use during both periods. For severe psychological distress, the aORs (95% CrIs) were 1.07 (0.97–1.19) and 1.50 (1.15–1.94), respectively.
Conclusions
A dose–response-like pattern was observed, suggesting that even limited antibiotic use may be an independent risk factor for psychological distress during early- to mid-pregnancy, highlighting the importance of judicious antibiotic use from the preconception period.
