Learning from a negative trial of lockable pesticide storage
Authors: Paul Yip
Journal: The Lancet (2017)

With a view to reducing pesticide self-poisoning in Sri Lanka, Melissa Pearson and colleagues1Pearson M Metcalfe C Jayamanne S et al.Effectiveness of household lockable pesticide storage to reduce pesticide self-poisoning in rural Asia: a community-based, cluster-randomised controlled trial.Lancet. 2017; (published online Aug 11.)http://dx.doi.org/10.1016/S0140-6736(17)31961-XSummary Full Text Full Text PDF Scopus (57) Google Scholar did one of the largest community-based cluster-randomised controlled trials of the effectiveness of household lockable pesticide storage, reported in The Lancet. The effort is admirable, but unfortunately their results show that improved household pesticide storage did not reduce the incidence of pesticide self-poisoning. In the study, households in 90 rural villages in North Central Province, Sri Lanka, that had farmed or had used or stored pesticides in the preceding agricultural season were randomly assigned to receive a lockable storage container, or no intervention, amounting to 27 091 households (114 168 individuals) in the intervention group and 26 291 households (109 693 individuals) in the control group. In individuals aged 14 years or older, 611 cases of pesticide self-poisoning had occurred by 3 years in the intervention group compared with 641 cases in the control group. The primary outcome, incidence of pesticide self-poisoning, did not differ between groups (293·3 per 100 000 person-years of follow-up in the intervention group vs 318·0 per 100 000 in the control group; p=0·33). The investigators found no evidence of switching from pesticide self-poisoning to other forms of self-harm, with no significant difference in the number of fatal (82 in the intervention group vs 67 in the control group) or non-fatal (1135 vs 1153) self-harm events involving all methods. Discouraging though these findings may seem, they are valuable in providing insights into the understanding of the complexities of any suicide prevention effort.2Hawton K van Heeringen K Suicide.Lancet. 2009; 373: 1372-1381Summary Full Text Full Text PDF PubMed Scopus (1418) Google Scholar, 3Yip PSF Caine E Yousuf S Chang SS Wu KCC Chen YY Means restriction for suicide prevention.Lancet. 2012; 379: 2393-2399Summary Full Text Full Text PDF PubMed Scopus (333) Google Scholar Suicide is not a disease reflecting well defined pathological mechanisms, and the occurrence of suicidal behaviour is usually the outcome of complex interactions of socioenvironmental, behavioural, and psychiatric factors.4Mann JJ Apter A Bertolote J et al.Suicide prevention strategies: a systematic review.JAMA. 2005; 294: 2064-2074Crossref PubMed Scopus (2118) Google Scholar Restricting access to lethal means of suicide has received much empirical support, this method being most effective among sudden, unplanned suicides, because those victims tend to use the method most readily accessible to them.5Yip PSF Lee DTS Charcoal-burning suicides and strategies for prevention.Crisis. 2007; 28: 21-27Crossref PubMed Scopus (63) Google Scholar, 6Knox KL Conwell Y Caine ED If suicide is a public health problem, what are we doing to prevent it?.Am J Public Health. 2004; 94: 37-45Crossref PubMed Scopus (188) Google Scholar If a lethal method is not available at the moment of the potential deadly action, it might be possible to buy time so that (in some cases at least) suicidal impulses will fade without fatal consequences. Even when suicides are planned, difficulty in gaining access to the most lethal means of suicide can serve as a substantial impediment. Nonetheless, this proposed method per se seems not sufficient enough to lower pesticide poisoning, suicide, or self-harm rates at the community level. Since highly lethal pesticides and the keys to their storage are still within reach in the household, no other less lethal method is a better substitute for pesticide suicides in such cases. Because the causes of suicides are multifactorial, restriction of means needs to be incorporated into a holistic and integrated suicide prevention programme rather than as a stand-alone measure. Suicide is still a rare event. Despite the fairly large number of households involved in the study it was still not large enough to detect differences, especially because non-compliance in the intervention group was not small: about 30% in the first year and 50% in the third, and some lockable pesticide storage was used in the control region. Furthermore, because of the close proximity of the intervention and the control sites, a contamination effect might have occurred. Hence, we cannot infer from this specific intervention (household lockable pesticide storage) that restriction of means is not useful in preventing suicides, because many studies have demonstrated its effectiveness.7WHOWorld suicide report. World Health Organization, Geneva2014http://www.who.int/mental_health/suicide-prevention/world_report_2014/en/Google Scholar The more important and relevant question is why does this specific intervention not produce a desirable result in the setting of Sri Lanka? Is it that the proposed restriction method is not secure enough to achieve the target of deterrence and buying time for any intervention to take place? Undoubtedly, lockable storage might help to reduce the risk of self-harm or suicide in some impulsive individuals. The deterrent effect seems to be greatly compromised compared with the removal of highly hazardous pesticides in the agricultural environment, as suggested by the investigators.1Pearson M Metcalfe C Jayamanne S et al.Effectiveness of household lockable pesticide storage to reduce pesticide self-poisoning in rural Asia: a community-based, cluster-randomised controlled trial.Lancet. 2017; (published online Aug 11.)http://dx.doi.org/10.1016/S0140-6736(17)31961-XSummary Full Text Full Text PDF Scopus (57) Google Scholar In Hong Kong and Taiwan, however, my experience with colleagues in restricting the availability of charcoal in reducing charcoal-burning suicides, was more encouraging.8Yip PSF Law CK Fu KW Law YW Wong PW Xu Y Restricting the means of suicide by charcoal burning.Br J Psychiatry. 2010; 196: 241-242Crossref PubMed Scopus (69) Google Scholar, 9Chen YY Chen F Chang SS Wong J Yip PSF Assessing the efficacy of restricting access to barbecue charcoal for suicide prevention in Taiwan: a community-based intervention trial.PLoS One. 2015; 10: e0133809Google Scholar Barbecue charcoal was removed from open shelves and put in locked storage where the customers had to ask a shop assistant before they could obtain it. This obstacle in the purchase of charcoal (which can result in a 10–15 min delay) decreased the rates of charcoal-burning suicides with no clear evidence of substitution (ie, the adoption of alternative methods). However, we were not able to study this intervention in a randomised controlled trial because of the constraints imposed by the participating supermarkets. Other related initiatives have reduced self-harm or suicides, including the change from coal gas to non-toxic gas in the UK,10Kreitman N The coal gas story. United Kingdom suicide rates, 1960-71.Br J Prev Soc Med. 1976; 30: 86-93PubMed Google Scholar installation of platform safety doors in the railway system,11Law CK Yip PS Chan WS Fu KW Wong PW Law YW Evaluating the effectiveness of barrier installation for preventing railway suicides in Hong Kong.J Affect Dis. 2009; 114: 254-262Summary Full Text Full Text PDF PubMed Scopus (72) Google Scholar and the reduction in prescribing barbiturates.12Chen YY Wu KCC Yousuf S Yip PSF Suicide in Asia: opportunities and challenges.Epidemiol Rev. 2012; 34: 129-144Crossref PubMed Scopus (225) Google Scholar However, because the effect of any restriction measure will decline as the community gets used to it, continuous reinforcement and innovative engagement are needed to sustain the impact of the means restriction.9Chen YY Chen F Chang SS Wong J Yip PSF Assessing the efficacy of restricting access to barbecue charcoal for suicide prevention in Taiwan: a community-based intervention trial.PLoS One. 2015; 10: e0133809Google Scholar Despite its finding of no effect, the unique study by Pearson and colleagues has provided much reflection on the complexity of suicide prevention and research. There is no silver bullet for suicide prevention and it needs to be understood, implemented, and interpreted in the local context. Pesticide poisoning still accounts for 20–30% of suicides worldwide, especially in populous countries such as India and China.7WHOWorld suicide report. World Health Organization, Geneva2014http://www.who.int/mental_health/suicide-prevention/world_report_2014/en/Google Scholar More innovative methods should be further explored to save lives.7WHOWorld suicide report. World Health Organization, Geneva2014http://www.who.int/mental_health/suicide-prevention/world_report_2014/en/Google Scholar I declare no competing interests. Effectiveness of household lockable pesticide storage to reduce pesticide self-poisoning in rural Asia: a community-based, cluster-randomised controlled trialWe found no evidence that means reduction through improved household pesticide storage reduces pesticide self-poisoning. Other approaches, particularly removal of highly hazardous pesticides from agricultural practice, are likely to be more effective for suicide prevention in rural Asia. Full-Text PDF Open Access