Introduction Psychological factors have been implicated to be etiologies for idiopathic environmental illness (IEI) in many studies. No study has ever been conducted to investigate the relationship of electromagnetic hypersensitivity (EHS) and psychiatric morbidity. Moreover, no published study has ever reported the psychiatric co-morbidity rate among people with IEI in a population-based survey. This study aimed to investigate the prevalence and characteristics of people with self-reported electromagnetic field sensitivity (SREMFS), especially the psychiatric co-morbidity, in adult population of Taiwan. Participants and procedure Questions regarding hypersensitivity to EMF were included in a telephone survey of environmental health risk perception conducted in Participants were adults selected from nation-wide households registered in the database of the Computer-Assisted Telephone Interviewing system via a two-stage geographically stratified systematic sampling. Households were randomly selected from each area according to proportional population size in 25 geographical areas of Taiwan. One respondent was selected randomly among eligible persons in the household. In total, telephone numbers were selected. Of those, 5643 households could be reached. Only 1251 individuals completed the interview (response rate = 17.8% and cooperation rate = 32.5%). Sample weights were adjusted for age, gender, and education derived from the nation-wide population in the end of year Statistical analyses were performed with the software package STATA Department of Psychiatry, National Taiwan University Hospital Yun-Lin Branch and College of Medicine, National Taiwan University, Taipei, Taiwan 2 Institute of Occupational Medicine and Industrial Hygiene, College of Public Health, National Taiwan University, Taipei, Taiwan 3 Institute of Science,Technology, and Society, School of Humanities and Social Sciences, National Yang Ming University, Taipei, Taiwan Prevalence and psychiatric co-morbidity of self-reported electric and magnetic field sensitivity in Taiwan: A population-based study Mei-Chih Meg Tseng 1,2, Yi-Ping Lin 3, Tsun-Jen Cheng 2 Questionnaire The interview content consists of questions regarding demographic variables, presence of catastrophic illness, self-reported health condition, and risk perception of various environmental agents, impairment of functioning, as well as medical utilization. EHS was defined as self-referred to be “allergic or very sensitive to getting near any electromagnetic field”, and degree of allergic or sensitivity was rated on a 4-point Likert scale. People with psychiatric morbidity were identified by a screening questionnaire, the Brief Symptom Rating Scale-5 (BSRS-5), with a cutoff score at 6 (sensitivity = 78.8%, specificity = 74.3%, PPV = 69.9%, and NPV = 82.3%). The BSRS-5 comprises 5 items, i.e., anxiety, depression, hostility, interpersonal sensitivity and sleep difficulties. Results The study sample contained the same gender proportion, more middle-aged and higher educated participants than the 2007 general population of Taiwan. General characteristics for people with SREMFS (n = 170) and survey population (n = 1197) with complete data were shown in Table 1. The estimated prevalence of people with SREMFS was 13.3 % (95% C.I. = 11.2, 15.3). The weighted psychiatric co-morbidity rate among people with SREMFS was 30.7% (95% C.I. = 23.6, 38.9). Dose-response relationship existed between prevalence of psychiatric morbidity and severity of SREMFS (Fig 1). People with age above 65-year-old was associated with a lower risk of reporting hypersensitivity to EMF, while people with very poor self-reported health status, being unable to work, and with psychiatric morbidity were associated with a higher risk of having SREMFS (Table 2). Discussion The error in the estimation of prevalence of SREMFS resulting from the selection bias in survey respondents was thought to be minimal based on the fact that the percentage of catastrophic illness in our survey (3.3%) was comparable to that of the general population (3.3%) (Bureau of National Health Insurance 2008). The possible under-estimation of prevalence of SREMFS resulting from over-represented high educated and middle-aged women commonly seen in telephone survey sample was minimized by weight adjustment according to the nation-wide population. The prevalence of SREMFS in Taiwan is higher than that of the Western countries (1.5-5%) (Hillert et al. 2002; Levallois et al. 2002; Schreier et al. 2006). People with psychiatric morbidity were more likely to report hypersensitivity to EMF. The effect of psychiatric morbidity on SREMFS needs to be studied further.