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Note: This study found no significant biological effects under its experimental conditions. We include all studies for scientific completeness.

Brain & Nervous System

Effects of pulsed high-frequency electromagnetic fields on the neuroendocrine system

No Effects Found

Mann, K, Wagner, P, Brunn, G, Hassan, F, Hiemke, C, Roschke, J · 1998

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EMF exposure at cell phone levels caused a temporary stress hormone spike, suggesting the body recognizes EMF as a biological stressor.

Plain English Summary

Summary written for general audiences

Researchers exposed healthy volunteers to 900 MHz electromagnetic fields (similar to older cell phones) while they slept and measured hormone levels throughout the night. They found a small, temporary increase in cortisol (stress hormone) right after exposure began, but no effects on growth hormone, reproductive hormones, or melatonin. The study suggests our bodies may quickly adapt to this type of EMF exposure.

Why This Matters

This study provides valuable insight into how EMF exposure affects our hormone systems during sleep, when many critical biological processes occur. The 900 MHz frequency tested matches older GSM cell phone technology, and the power density of 0.02 mW/cm² is actually quite low compared to typical phone usage near the head. What's particularly interesting is the transient cortisol spike - even though it lasted only an hour, cortisol is our primary stress hormone, and any elevation suggests the body is responding to EMF as a potential stressor. The researchers' conclusion about 'adaptation' may be premature, as we don't fully understand whether repeated cortisol responses over time could have cumulative health implications. While this study found minimal effects, it's worth noting that hormone disruption can have subtle but significant long-term consequences, and this research represents just one data point in a much larger body of evidence examining EMF's biological effects.

Exposure Details

Power Density
0.02 mW/cm²
Source/Device
900 MHz

Exposure Context

This study used 0.02 mW/cm² for radio frequency:

Building Biology guidelines are practitioner-based limits from real-world assessments. BioInitiative Report recommendations are based on peer-reviewed science. Check Your Exposure to compare your own measurements.

Where This Falls on the Concern Scale

Study Exposure Level in ContextStudy Exposure Level in ContextThis study: 0.02 mW/cm²Extreme Concern - 1,000 µW/m²FCC Limit - 10M µW/m²Effects observed in the Extreme Concern range (Building Biology)FCC limit is 50 times higher than this level
A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 900 MHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 900 MHzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Study Details

To investigate the influence of pulsed High-Frequency Electromagnetic Fields on the Neuroendocrine System

The influence of pulsed high-frequency electromagnetic fields emitted from a circularly polarized an...

An alteration in the hypothalamo-pituitary-adrenal axis activity was found with a slight, transient ...

The results indicate that weak high-frequency electromagnetic fields have no effects on nocturnal hormone secretion except for a slight elevation in cortisol production which is transient, pointing to an adaptation of the organism to the stimulus.

Cite This Study
Mann, K, Wagner, P, Brunn, G, Hassan, F, Hiemke, C, Roschke, J (1998). Effects of pulsed high-frequency electromagnetic fields on the neuroendocrine system Neuroendocrinology 67(2):139-144, 1998.
Show BibTeX
@article{mann_1998_effects_of_pulsed_highfrequency_3227,
  author = {Mann and K and Wagner and P and Brunn and G and Hassan and F and Hiemke and C and Roschke and J},
  title = {Effects of pulsed high-frequency electromagnetic fields on the neuroendocrine system},
  year = {1998},
  
  url = {https://www.karger.com/Article/Abstract/54308},
}

Quick Questions About This Study

A 1998 study found that 900 MHz electromagnetic fields caused a small, temporary increase in cortisol (stress hormone) immediately after exposure began during sleep. This elevation lasted about one hour, then returned to normal, suggesting the body quickly adapts to this type of EMF exposure.
Research from 1998 found that 900 MHz electromagnetic fields (similar to older cell phones) had no significant effects on melatonin production during nighttime sleep. The study measured hormone levels throughout the night and found melatonin secretion patterns remained unchanged under EMF exposure.
A controlled sleep study found that 900 MHz electromagnetic field exposure had no significant effects on growth hormone production during the night. Researchers measured hormone levels in healthy volunteers and found no changes in total growth hormone production or secretion patterns.
Research exposing healthy volunteers to 900 MHz electromagnetic fields during sleep found no significant effects on luteinizing hormone (LH) production. The study measured reproductive hormone levels throughout the night and found no changes in total hormone production or secretion patterns.
A 1998 study found that pulsed 900 MHz electromagnetic fields caused no significant changes in sleep EEG brain wave patterns. While researchers noted a slight trend toward reduced REM sleep, this effect was not statistically significant compared to placebo conditions.