title: Nocebo responses to high-voltage power lines: Evidence from a prospective field study.
abstract: BACKGROUND
  Experimental studies suggest that nocebo responses might occur after exposure to equipment emitting electromagnetic fields such as high voltage power lines (HVPLs) or mobile phone base stations.
  
  
  OBJECTIVE
  The present study investigates to what extent health responses to a new HVPL can be explained by beliefs of residents regarding the health effects of HVPLs.
  
  
  METHODS
  We used a quasi-experimental prospective field study design with two pretests during the construction of a new HVPL, and two posttests after it has been put into operation. Residents living near (0-300 m, n=229; 300-500 m, n=489) and farther away (500-2000 m, n=536) filled out questionnaires about their health and their beliefs about the negative health effects of power lines. Longitudinal mediation models were applied to investigate to what extent these beliefs could explain a change in reported symptoms after the new line was put into operation.
  
  
  RESULTS
  Significant (p<.01) indirect effects were found for proximity on the increase in reported cognitive (R(2)=0.41) and somatic (R(2)=0.79) symptoms after the power line was put into operation through an increase in the belief that power lines causes health effects. The direct effects of proximity on an increase in reported symptoms were not significant.
  
  
  CONCLUSIONS
  Our findings suggest that increases in reported health complaints after a new HVPL has been put into operation can be explained by nocebo mechanisms. Future field studies are needed to know whether our findings extend to other environmental health issues in a community.
authors.affiliation: Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Jarry T
authors.initials: JT
authors.lastname: Porsius
authors.affiliation: Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands; National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Claassen
authors.affiliation: Municipal Health Service, Amsterdam, The Netherlands.
authors.forename: Fred
authors.initials: F
authors.lastname: Woudenberg
authors.affiliation: Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands; KLM Health Services, Schiphol, The Netherlands.
authors.forename: Tjabe
authors.initials: T
authors.lastname: Smid
authors.affiliation: Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands; National Institute for Public Health and the Environment, Bilthoven, The Netherlands. Electronic address: drm.timmermans@vumc.nl.
authors.forename: Danielle R M
authors.initials: DRM
authors.lastname: Timmermans
mesh_terms: D011211:Electric Power Supplies; D004574:Electromagnetic Fields; D004781:Environmental Exposure / Q000032:analysis* / Q000706:statistics & numerical data; D006801:Humans; D064786:Nocebo Effect; D011446:Prospective Studies; D011795:Surveys and Questionnaires
keywords: Electromagnetic fields; Environmental health risk; Nocebo; Power lines; Symptom reports