Research Pesticide exposure and suicidal ideation in rural communities in Zhejiang province, China Jianmin Zhang,a Robert Stewart,b Michael Phillips,c Qichang Shi a & Martin Prince b Objective To investigate the association between pesticide exposure and suicidal ideation in rural areas of China. Methods The analysis involved data from a survey of a representative sample of 9811 rural residents in Zhejiang province who had been asked about the storage of pesticides at home and about whether or not they had considered suicide within the 2 years before the interview. The Chinese version of the 12-item General Health Questionnaire (GHQ) was administered to screen for mental disorder. Findings The unadjusted odds ratio (OR) for the association between pesticide storage at home and suicidal ideation over the prior 2 years was 2.12 (95% confidence interval, CI: 1.54–2.93). After adjusting for gender, age, education, socioeconomic status, marital status, physical health, family history of suicidal behaviour, GHQ caseness and study design effects, the OR was 1.63 (95% CI: 1.13–2.35). Conclusion A potential marker of chronic pesticide exposure was found to be associated with suicidal ideation, which supports findings from previous studies. Given the high level of pesticide exposure and the high suicide risk in rural China, clarification of the causal mechanisms underlying this association and the development of appropriate interventions are priorities for public health and health policy. الرتجمة العربية لهذه الخالصة يف نهاية النص الكامل لهذه املقالة. .Une traduction en français de ce résumé figure à la fin de l’article. Al final del artículo se facilita una traducción al español Introduction at home and recent suicidal ideation in rural China by ana- lysing data from a province-wide survey of mental disorders The use and availability of pesticides are significant concerns that was carried out in 2001 as part of a WHO and Chinese in the field of mental health, not only because these chemicals Ministry of Health project. are used in suicide attempts 1 but also because their possession may be directly associated with mental disorder. Suicide rates are reported to be higher in areas where organophosphates Methods are used 2 and exposure is a possible risk factor for Parkinson The study was performed in Zhejiang province, a densely disease 3,4 and Alzheimer disease,3 for depressive and anxiety populated coastal province of China that in 2000 had a 5,6 7 disorders and for mortality ascribed to mental disorder. total population of 45 million, 70% of which lived in rural 8,9 However, research in this area remains controversial. areas. It is one of the most developed provinces in China and Pesticides have been widely used in agriculture since the in 2000 had an average per capita gross domestic product 10 1950s but, despite precautionary measures, intentional and (GDP) of 13 461 renminbi (US$ 1660), the fourth highest occupational poisoning remain major concerns. For example, among China’s 31 provinces and independent municipalities. pesticide ingestion was implicated in 62% of suicides in China between 1996 and 2000, which corresponds to around Sample size 175 000 cases per year.1,11 The survey was designed to ascertain a prevalence of mental Suicide in China accounts for 44% of all suicides world- wide.12 Moreover, suicide is the fifth leading cause of death disorder of 15% with 1% precision. In addition, the sample in China13 overall and the leading cause in 15–34-year-olds.14 size was increased to 15 000 to enable comparisons to be made according to gender and urban or rural residence. The In rural areas, suicide rates are 2–5 times those in urban 17 areas13,15 and, in contrast to Western populations, the rate ratio of urban to rural residence was estimated to be 1:2. is higher in women than men.13 Although mental disorder, Sampling procedure especially depression, is associated with suicide,16 the link between suicide and mental disorder may be relatively weak The survey employed a multistage sampling process that has in China.13 The reasons for the high rate and unique pattern previously been described in detail by Shi et al.18 The sam- of suicide in China have yet to be established. pling frame was the province-wide computerized household Organophosphate pesticides are used widely in China registry, which was updated during the 2000 national census. and the potential for exposure is high. Despite this, the men- Seven indicators (i.e. population density, birth rate, the pro- tal health risks of prolonged exposure remain unclear. We portion of non-agricultural labourers, per capita GDP, illit- investigated the association between the storage of pesticides eracy rate, crude death rate and proportion aged > 65 years) a Office of Mental Health, Zhejiang Provincial Tongde Hospital, Hangzhou, China. b Institute of Psychiatry, King’s College London (Institute of Psychiatry), De Crespigny Park, London, SE5 8AF, England. c WHO Collaborating Center for Research and Training in Suicide Prevention, Beijing Hui Long Guan Hospital, Beijing, China. Correspondence to Robert Stewart (e-mail: [email protected]). (Submitted: 18 April 2008 – Revised version received: 10 December 2008 – Accepted: 23 January 2009 – Published online: 28 July 2009 ) Bull World Health Organ 2009;87:745–753 | doi:10.2471/BLT.08.054122 745 Research Pesticide exposure and suicidal ideation in China Jianmin Zhang et al. for 11 cities and 63 rural counties were sample at that location (n = 567), covariates were age, sex, years of formal subjected to a principal components neighbouring households of the target education, marital status, annual per factor analysis. Two factors accounted subjects (n = 2133) and, for two sites capita household income (in three for 65.2% of the variance. The factor at which most residents had relocated, strata), family history of suicidal be- scores were then used to construct five neighbouring communities (n = 672). haviour, and subjective global physical strata: (i) 5 cities (comprising 45.5% of health status in the prior month, which the total urban population); (ii) 6 cities Assessments was categorized on a 5-point scale and (comprising 54.5% of the total urban Interviews were carried out in study then dichotomized to “poor health” population); (iii) 19 counties (compris- participants’ homes by 34 trained psy- versus “others”. The rural stratum of ing 30.2% of the total rural popula- chiatric nurses between September and the participant was also considered as tion); (iv) 13 counties (comprising December 2001. All participants pro- a covariate and as an effect modifier. 20.6% of the total rural population); vided verbal informed consent after the For unadjusted analyses, the three ru- and (v) 31 counties (comprising 49.2% study had been fully explained. Local ral strata were ordered according to the of the total rural population). This ethics review boards were not in place frequency of suicidal ideation, although analysis considered only the three rural at the time of the survey. According this ordering differed from that of the strata, which broadly corresponded to to standard practice at that time, the socioeconomic indices (i.e. the order mountain, plains and coastal regions. survey was initially considered and ap- of areas with ascending socioeconomic Groups of three, two and five proved by WHO and further consider- indices were mountain followed by counties were selected from the three ation and approval were then provided coastal followed by plains regions). rural strata (mountain, plains and by the Department of Disease Control coastal regions, respectively) by sam- and the Department of International Statistical analysis pling in proportion to the population Cooperation at the Chinese Ministry Statistical weighting was applied so aged 15 years or over. Thereafter, five of Health, as well as by the Mental that the participants selected accurately districts within each county and, sub- Health Leading Group of Zhejiang represented the total population of sequently, two villages within each province. The principal independent Zhejiang province. Within each cluster district were sampled in proportion to variable considered in this analysis was (i.e. each village), the initial weight their populations. Systematic random the storage of pesticides at home. In was the number of individuals in the sampling was used in each stratum households where informants reported population represented by the cluster to select the counties, districts, and storing pesticides (excluding rodenti- divided by the number of completed villages. A total of 100 villages were cides), the type of pesticide and method interviews in that cluster. Thus, the selected from the 50 rural districts of storage were recorded. weight incorporated an adjustment for sampled from the 10 counties. The final stage of sampling, which was again All participants were asked the individuals included in a sample but carried out in proportion to popula- following questions: “Have you ever not interviewed. In addition, weights tion size, involved the identification of considered suicide or deliberate self- were further adjusted to reduce the ef- 1000 residents aged 15 years or more harm in your lifetime?”, “Have you fect of extreme weights: in clusters in in each of the 10 counties. At each vil- ever planned suicide or deliberate self- which the weight was greater than two lage, simple random selection was used harm in your lifetime?”, and “Have you standard deviations above the average to identify target subjects from the ever attempted suicide or deliberate weight, the value was reduced to equal computerized registry of community self-harm in your lifetime?”. If any of two standard deviations. Finally, post- residents. The demographic character- the above were answered positively, stratification weights were obtained to istics of the selected population sample further questions were asked about compensate for any mismatch between were similar to those of the province the respondent’s age at the first and the age and gender distributions of each as a whole.17 At each village, a 20% most recent episode or occurrence.