Nationwide Japanese Study Links Periconceptional Antibiotic Use to Increased Risk of Psychological Distress During Pregnancy

A Japanese study of 94,000 women finds that using antibiotics before or during early pregnancy is tied to a 50% higher risk of severe psychological distress.

By: AXL Media

Published: Apr 2, 2026, 4:42 AM EDT

Source: Information for this report was sourced from University of Toyama.

The Biological Intersection of Infection and Mental Health

Perinatal depression and psychological distress are among the most pervasive health challenges faced by women, impacting not only the mother’s well-being but also the long-term developmental trajectory of the child. While many factors contribute to maternal mental health, emerging research is increasingly focusing on the unintended consequences of common medical interventions. A new study led by Professor Kenta Matsumura, involving nearly 100,000 participants in Japan, suggests that the use of antibiotics in the months surrounding conception may play a role in triggering psychological distress. This research adds a new dimension to the global conversation regarding the appropriate use of antibiotics, suggesting that their impact may extend far beyond the treatment of bacterial infections.

Analyzing Data from the Japan Environment and Children's Study

The researchers utilized an extensive dataset from the Japan Environment and Children's Study (JECS), a nationwide birth cohort designed to track how environmental exposures influence maternal and child health. The study focused on 94,490 pregnant women, primarily at the 12-to-15-week mark of their pregnancy. By documenting antibiotic use during two distinct phases—before pregnancy recognition and after recognition—the team was able to categorize participants based on the duration and frequency of their exposure. This large-scale statistical approach allowed the researchers to isolate antibiotic use as a key variable while controlling for a wide array of socio-economic and lifestyle factors.

Quantifying the Odds of Psychological Distress

To measure mental health outcomes, the team employed the Kessler Psychological Distress Scale (K6), a standardized six-item questionnaire that assesses the severity of a participant's emotional state. The results showed a clear, "stepwise" increase in risk associated with antibiotic use. For those experiencing moderate psychological distress, the odds increased by 12% if they used antibiotics in one period and 22% if they used them in both. The correlation was even more pronounced in cases of severe psychological distress, where women who used antibiotics across both periods faced a 50% higher likelihood of significant mental health struggles compared to those who used none.