An important area of the consequences of noise relates to task performance. Laboratory studies have shown that noise exposure increases arousal and can improve cognitive performance on simple tasks that require vigilance. On the other hand, noise can interfere with more complex tasks, decreasing attention as well as altering choice of task strategy.9
In the so-called irrelevant speech effect, cognitive performance can be disturbed when the individual hears background speech that is irrelevant to the task; it is believed that this may interfere with memory processes.10 This phenomenon has obvious implications for people working in open-plan offices.
Recent epidemiologic studies of schoolchildren have found that aircraft noise exposure at school was associated in a linear exposure-effect relationship with impairment of reading and memory recognition,11 which confirmed earlier studies.12 The mechanism for this is uncertain; it may relate to disturbances in communication between teachers and pupils or maladaptive attentional strategies.Mental health and noise
Because of its effects on annoyance, sleep, and cognitive performance, noise might be expected to affect mental health. Although there is some evidence of this effect, the data are by no means clear-cut.
At the simplest level, noise exposure in the community has been related to an increased incidence of psychological symptoms, including headaches, anxiety, fatigue, and depression.13,14 Early studies of mental hospital admissions and aircraft noise exposure showed a mixed picture,15 and community surveys, which are a more appropriate design for detecting the effects of environmental noise, have only shown effects in certain subgroups.16
Two epidemiologic studies of road traffic noise have found associations between noise exposure and symptoms of mental distress17 and anxiety scores.18 A more recent Sardinian study19 examined persons living close to an airport and matched them with controls. Researchers found a higher prevalence of generalized anxiety disorder, as diagnosed by the Composite International Diagnostic Interview, among those exposed to high levels of aircraft noise than among people living in quieter areas.
Relationships between military aircraft noise exposure and psychological distress have been found in a range of Japanese studies, suggesting there may be more evidence for effects on mental health at higher noise levels. Increased levels of prescriptions of hypnotics and nonprescription sedatives in areas exposed to aircraft noise (compared with those in quieter areas) can be considered indirect evidence of the mental health effects of noise.20,21
Thus, there is a need for more research to provide additional insight and perhaps stronger evidence for the link between noise and psychological distress. It should be noted that noisy environments are often socioeconomically disadvantaged environments, and it is difficult to disentangle the effect of noise on mental health from the effects of other stressors, both social and environmental, that may be present.Mental illness, neighbors, and noise
Noise from neighbors has received little research investigation but may come to the attention of psychiatrists. In the United Kingdom, this is the most common source of noise complaints to local government authorities.22
Noise that is continuous, apparently indefinite, of uncertain cause or source, emotive or frightening, or apparently due to thoughtlessness or lack of consideration is most likely to elicit an adverse reaction.23
In some cases, on further inquiry, it becomes apparent that complaints of noise disturbance are related to persecutory delusions and may be a symptom of psychosis. In these cases, which often come to the attention of psychiatrists, the disturbances are typically part of a wider system of persecutory ideas about neighbors, in which noise is only one of many afflictions that the patient believes the neighbors are causing him or her. Here, the management relates to the primary underlying illness, for which risk assessment (including assessment of the risk of aggression against neighbors) will be important. On the other hand, the clinician should not be too ready to dismiss the reality of the noise complaints.
Prolonged exposure to noise can be very upsetting and intrusive and can interfere with sleep and everyday activities, especially in poorly built dwellings, where even low-intensity noises from neighbors may be clearly audible. This may be a problem particularly among people who are chronically anxious and who complain of sensitivity to noise (ie, prolonged noise exposure may make them more anxious and unhappy).
There may be a phobic reaction to noise in some people with noise sensitivity that might respond to a cognitivebehavioral approach.24 There is evidence that people with existing depression and anxiety are more likely to be sensitive to the effects of noise.24
Perceptions of lack of control over the noise, unpleasant meanings associated with the noise, or a feeling that others don't care may exacerbate negative responses. Active coping strategies, such as shutting windows, spending more time in the most quiet areas of their residence, and complaining to the relevant authorities, may reduce negative responses to noise. Conversely, passive coping is likely to aggravate noise effects.Concluding thoughts
Current evidence suggests that environmental noise exposure, especially at higher levels, is related to mental health symptoms and possibly to increased anxiety and consumption of sedative medication. Although noise exposure may be responsible for only relatively mild psychiatric disorders, it does involve large numbers of people whose quality of life may be impaired significantly. For the fifth of the population who are sensitive to noise, chronic noise exposure can cause considerable disturbance and misery.16
Dr Stansfeld is professor of psychiatry at the Centre for Psychiatry, Wolfson Institute of Preventive Medicine, Barts, and The London Queen Mary's School of Medicine and Dentistry, London. He is also secretary of the International Commission on the Biological Effects of Noise and has a long-standing interest in research on noise and health.
Dr Stansfeld is a consultant on a project on noise and vibration impact assessment sponsored by the United Kingdom Department of Environment.