Systematic review of methodological limitations in electromagnetic hypersensitivity studies (Schmiedchen et al. 2019)

Review article

From a scientific point of view, many uncertainties exist regarding electromagnetic hypersensitivity (EHS). While there are numerous individuals who claim to suffer from health problems due to EMF
exposure, many experimental studies conducted on this topic have not been able to establish a causal relationship with EMF.

The systematic review conducted by Schmiedchen et al. (2019) focused on published blinded experimental studies in volunteers in the frequency range from 0 to 300 GHz with study participants claiming to suffer from EHS. The analysis aimed at evaluating these studies with regard to their methodological limitations, since the respective study approaches can lead to biased results due to implicit assumptions. The authors performed a “risk of bias” assessment by evaluating the individual studies with regard to possible systematic bias. Such bias can occur, for example, if some of the study participants had physical illnesses that could explain their EHS symptoms, or due to the sequence and duration of the exposure conditions applied, since these can result in different stress levels.

A total of 28 studies were included in the analysis, 7 of which found statistically significant associations between EMF exposure and health effects in EHS persons. Both increased and decreased occurrence of symptoms was observed under exposure conditions. However, 21 studies found no evidence that the symptoms reported by the study participants were related to EMF exposure. For 82% of the studies examined, the authors criticized the heterogeneity of the study participants, as the exposure scenarios applied were probably not suitable for some of the participants. This could have led to false negative results (i.e. a study does not find a link between exposure and symptoms, eventhough it does exist) if effects only occur under very specific exposure conditions. The results of studies with relatively few methodological limitations show less likely exposure-related effects. In almost one third of the studies examined, the nocebo effect plays a role with regard to symptoms in people with EHS. According to the authors, this review suggests absence of a causal relationship between EMF exposure and health effects.

However, it still cannot be ruled out that there might be weak health
effects, or some individuals who actually do react to EMF. For future studies, the authors thus recommend to identify subgroups and to conduct studies at the individual level.


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