Noise, noise sensitivity and psychiatric disorder: epidemiological and psychophysiological studies.

Noise, a prototypical environmental stressor, has clear health effects in causing hearing loss but other health effects are less evident. Noise exposure may lead to minor emotional symptoms but the evidence of elevated levels of aircraft noise leading to psychiatric hospital admissions and psychiatric disorder in the community is contradictory. Despite this there are well documented associations between noise exposure and changes in performance, sleep disturbance and emotional reactions such as annoyance. Moreover, annoyance is associated with both environmental noise level and psychological and physical symptoms, psychiatric disorder and use of health services. It seems likely that existing psychiatric disorder contributes to high levels of annoyance. However, there is also the possibility that tendency to annoyance may be a risk factor for psychiatric morbidity. Although noise level explains a significant proportion of the variance in annoyance, the other major factor, confirmed in many studies, is subjective sensitivity to noise. Noise sensitivity is also related to psychiatric disorder. The evidence for noise sensitivity being a risk factor for psychiatric disorder would be greater if it were a stable personality characteristic, and preceded psychiatric morbidity. The stability of noise sensitivity and whether it is merely secondary to psychiatric disorder or is a risk factor for psychiatric disorder as well as annoyance is examined in two studies in this monograph: a six-year follow-up of a group of highly noise sensitive and low noise sensitive women; and a longitudinal study of depressed patients and matched control subjects examining changes in noise sensitivity with recovery from depression. A further dimension of noise effects concerns the impact of noise on the autonomic nervous system. Most physiological responses to noise habituate rapidly but in some people physiological responses persist. It is not clear whether this sub-sample is also subjectively sensitive to noise and whether failure to habituate to environmental noise may also represent a biological indicator of vulnerability to psychiatric disorder. In these studies noise sensitivity was found to be moderately stable and associated with current psychiatric disorder and a disposition to negative affectivity. Noise sensitivity levels did fall with recovery from depression but still remained high, suggesting an underlying high level of noise sensitivity. Noise sensitivity was related to higher tonic skin conductance and heart rate and greater defence/startle responses during noise exposure in the laboratory. Noise sensitive people attend more to noises, discriminate more between noises, find noises more threatening and out of their control, and react to, and adapt to noises more slowly than less noise sensitive people.(ABSTRACT TRUNCATED AT 400 WORDS)