Idiopathic Environmental Intolerance: A Comprehensive Model

Idiopathic environmental intolerance refers to a group of poorly understood health conditions characterized by heterogeneous somatic symptoms that occur in response to environmental triggers, but for which no physiological causes can be found. We focus on three varieties, namely symptoms attributed to (a) chemical substances, (b) electromagnetic fields, and (c) infrasound and vibroacoustic sources. As no clear link with organ pathology or dysfunction has been established so far, we review critical evidence about alternative causal mechanisms as a platform for a novel unifying model of these conditions. There is consistent evidence that expectancy and nocebo mechanisms are critically involved. Using recent predictive coding models of brain functioning, we describe a comprehensive new model to explain how symptoms come about and become linked to specific environmental cues. This new model integrates phenomenally different pathologies, suggests testable new hypotheses, and specifies implications for treatment.