Title Suicide epidemics : The impact of newly emerging methods onoverall suicide rates-A time trends study

Background: The impact of newly emerging, popular suicide methods on overall rates of suicide has not previously been investigated systematically. Understanding these effects may have important implications for public health surveillance. We examine the emergence of three novel methods of suicide by gassing in the 20 and 21 centuries and determine the impact of emerging methods on overall suicide rates. Methods: We studied the epidemic rises in domestic coal gas (1919-1935, England and Wales), motor vehicle exhaust gas (1975-1992, England and Wales) and barbecue charcoal gas (1999-2006, Taiwan) suicide using Poisson and joinpoint regression models. Joinpoint regression uses contiguous linear segments and join points (points at which trends change) to describe trends in incidence. Results: Epidemic increases in the use of new methods of suicide were generally associated with rises in overall suicide rates of between 23% and 71%. The recent epidemic of barbecue charcoal suicides in Taiwan was associated with the largest rise in overall rates (40-50% annual rise), whereas the smallest rise was seen for car exhaust gassing in England and Wales (7% annual rise). Joinpoint analyses were only feasible for car exhaust and charcoal burning suicides; these suggested an impact of the emergence of car exhaust suicides on overall suicide rates in both sexes in England and Wales. However there was no statistical evidence of a change in the already increasing overall suicide trends when charcoal burning suicides emerged in Taiwan, possibly due to the concurrent economic recession. Conclusions: Rapid rises in the use of new sources of gas for suicide were generally associated with increases in overall suicide rates. Suicide prevention strategies should include strengthening local and national surveillance for early detection of novel suicide methods and implementation of effective media guidelines and other appropriate interventions to limit the spread of new methods. Background Suicide is among the leading causes of premature mortality in the world [1]. In 2004 suicide was the 8 leading cause of potential years of life lost among 15 to 44 year olds worldwide [1]. Whilst social, economic, cultural and psychological factors are significant contributors to suicide rates, there is good evidence that the changing availability and popularity of lethal methods are also important [2-4]. To date, most studies investigating associations between method availability and suicide rates have focused on the impact of limiting access to methods, such as the detoxification of the domestic gas supply in the 1950s and 1960s, the introduction of catalytic converters reducing the toxicity of car exhausts in the 1990s and the withdrawal of co-proxamol in recent years in the UK [5,6]. By the time these restrictions are put in place, many deaths may have already been caused by a particular method. Little attention has been paid to the impact of newly emerging methods on suicide rates, although the recent epidemics of charcoal burning suicides in Hong Kong and Taiwan have been well documented [7]. The rapid rise in the popularity of charcoal * Correspondence: kyla.thomas@bristol.ac. uk School of Social and Community Medicine, University of Bristol, Bristol, UK Full list of author information is available at the end of the article Thomas et al. BMC Public Health 2011, 11:314 http://www.biomedcentral. com/1471-2458/11/314 © 2011 Thomas et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. burning in the Far East is thought to have been fuelled by the extensive media and internet coverage of suicides using this method [8]. However much less is known about the reporting of domestic gas and car exhaust gassing suicides during rapid increases in the use of these methods in England and Wales. The aim of this analysis is to compare the rate of increase of suicide by gassing that occurred during three periods of rapidly rising use of this method in two countries Taiwan and England and Wales at three different time periods in the 20 and 21 centuries. Different sources of gas were used in each epidemic domestic ("coal”) gas (1920s and 1930s in England and Wales), motor vehicle exhaust gas (1970s and 1980s in England and Wales) and barbecue charcoal gas (Taiwan 2000s). We assess whether the emergence of new methods leads to an increase in overall suicide rates. We also hypothesize that the speed of uptake of novel methods may have been lower before the widespread availability of television and the Internet. The first epidemic (coal gassing suicides in England and Wales) occurred before the widespread availability of television, the second (car exhaust gassing in England and Wales), before the widespread popularity of the Internet whereas the epidemic of barbecue charcoal burning suicides in Taiwan occurred after both types of media had become widely available.