Increased limbic system symptomatology and sensitizability of young adults with chemical and noise sensitivities.

We previously hypothesized that individual differences in (a) limbic system reactivity and (b) central nervous system sensitizability underlie vulnerability to environmental stimuli, not only in the controversial clinical condition multiple chemical sensitivity (MCS), but also in the general population. Earlier research has shown overlaps in the characteristics of persons who report noise and air pollutant sensitivities. This study assessed questionnaire responses of 897 young adult college students who reported high versus low frequency of illness from several environmental chemical odors and concomitantly high versus low sensitivity to environmental noise. Subjects who reported increased rates of illness from chemical odors with or without noise sensitivity scored significantly higher (P < 0.0001) on a measure of limbic system symptomatology derived from ictal sensory, somatic, mnemonic, and behavioral manifestations of temporal lobe epilepsy. The group rating high both for illness from chemicals and for noise sensitivity had characteristics predictive of heightened sensitizability from the animal research on time-dependent sensitization (progressive response amplification to repeated, intermittent stimuli over time): i.e., higher female to male ratio (gender risk factor), increased rates of drug abuse problems in blood relatives (genetic risk factor), trait shyness (hyperreactivity to novelty), and increased carbohydrate craving. Despite the increased family histories of drug abuse and levels of personal anxiety and depression, the chemical- and noise-sensitive group reported the lowest rates of current smoking or personal drug abuse problems and the highest frequency of illness from drinking a small amount of alcohol. Taken together, the findings suggest that limbic system dysfunction associates more with chemical than with noise sensitivity; that individuals with both chemical and noise sensitivity may be the most sensitizable subset of the population for prospective studies, and that, in their substance use patterns, young adults with both chemical and noise sensitivity are more similar to MCS patients than are their peers with chemical or noise sensitivity alone.