Factors influencing suicide rates over the past 40 years

The availability and associated lethality of a range of suicide methods changed throughout our study period. Rates of suicide by gas poisoning rose from the early 1970s until 1992, before rapidly declining thereafter. This can be ascribed to the mandatory fitting of catalytic convertors in newly manufactured petrol motor vehicles from 1993 onwards. ^{Reference Kelly and Bunting27} More recently, reductions in the rate of suicide by solid and liquid poisoning may partially be explained by legislation to reduce the pack size of paracetamol and salicylates in 1998, ^{Reference Hawton, Bergen, Simkin, Dodd, Pocock and Bernal28} the withdrawal of co-proxamol sales in 2005 ^{Reference Hawton, Bergen, Simkin, Wells, Kapur and Gunnell29} and the transition in the prescribing of high-toxicity tricyclic to lower-toxicity selective serotonin re-uptake inhibitor (SSRI) antidepressants. ^{Reference Hawton, Bergen, Simkin, Cooper, Waters and Gunnell30} We found no clear evidence of a rise in suicides from 2003 onwards. This is reassuring given the Medicines and Healthcare Products Regulatory Agency activity to restrict prescribing of SSRIs to those aged below 18 years as a result of limited evidence of effectiveness and a concern that they may increase the risk of suicidal behaviour. ^{Reference Wheeler, Gunnell, Metcalfe, Stephens and Martin7} There was a substantial reduction in suicide deaths by jumping from the mid-1990s onwards for both males and females aged 15–19 years. This may have been because of the implementation of structural interventions to reduce the means of individuals jumping from notable suicide hot spots. ^{Reference Cox, Owens, Robinson, Nicholas, Lockley and Williamson31}

Despite relatively large reductions in suicides by gas poisoning, and solid and liquid poisoning, it is clear that suicide by hanging has partially substituted these and other methods of suicide over the past 40 years. This applies to all adolescents and is of particular concern because of the high case fatality rate of hanging as a method of suicide, and the relatively limited approaches available to professionals in preventing deaths by hanging. ^{Reference Gunnell, Bennewith, Hawton, Simkin and Kapur32} Our study period contained four periods of official recession: in the mid-1970s, early 1980s, early 1990s and most recently in the late 2000s. ^{Reference Hills and Thomas33} There is no clear evidence in our analysis that these influenced suicide rates in 10–19 year olds.

Strengths and limitations

This is the first comprehensive long-term investigation of trends in suicide deaths in adolescents in England and Wales. We were also able to explore the impact of deprivation on suicide rates in those aged 15–19 years. Although high-quality, national-level data were obtained, there are a number of limitations in our analysis.

First, the quality of reporting and its subsequent impact upon coding accuracy is an issue. There are widely divergent views in the literature regarding the capacity of younger adolescents aged 10–14 to (a) understand the concept of suicide and (b) intentionally end life. Consequently, accurate suicide rates in those aged 10–14 years, and to a lesser degree those aged 15–19 years, may be masked by a classification of some self-inflicted deaths as accidental, as opposed to suicide. ^{Reference Gunnell, Bennewith, Simkin, Cooper, Klineberg and Rodway14} We addressed this by including accidental deaths by hanging and poisoning in our analyses. Second, our study period saw two changes in ICD classifications used; one in 1990 (ICD-8 to ICD-9) and another in 2001 (ICD-9 to ICD-10). No discontinuities were evident when visually inspecting suicide rates and trends around these two periods. Further, previous analyses have shown that changes between versions have not influenced overall suicide rates. ^{Reference Pearson-Nelson, Raffalovich and Bjarnason34}

Third, some ICD code-specific methods of accidental poisoning (such as E850.0, X42; drugs of misuse, including opiates) and accidental hanging (such as W77; threat to breathing due to cave-in, falling earth and other substances) that have been included in our analyses are more likely to be genuine accidents rather than misclassified suicides. For accidental poisoning deaths, drugs of misuse accounted for around one-third of deaths (mostly in those aged 15–19 years), and there was evidence of a rise in deaths as a result of opiate use in the late 1990s. However, removal of these deaths in a sensitivity analysis had little impact on the observed trends. For accidental hanging, deaths coded as W77 are rare (<2% of accidental hanging deaths overall) and have a negligible effect on overall trends. A small number of accidental hanging deaths may also be attributed to a phenomenon known as the ‘Choking Game’. ^{Reference Busse, Harrop, Gunnell and Kipping35} Fourth, the number of suicide and accidental deaths in those aged 10–14 years was very small, with some years having no cases. This resulted in fluctuating rates, which were partially countered by using 3-year rolling averages centred on the middle year, and the calculation of weighted mean rates by decade. However, trends in this age group should be interpreted with caution.

Implications

Our analysis has provided further detail concerning rates and trends of various suicide methods in recent years. Of particular note is the increase in rates of suicide by hanging in all age groups across the past 40 years, particularly in females. The National Suicide Prevention Strategy for England places an emphasis on restricting means to access suicide. ^{Reference Government36} Given the continual increase in suicide by hanging in both younger and older adolescents, and the fact that only a small proportion of deaths by this method are amenable to method restriction ^{Reference Gunnell, Bennewith, Hawton, Simkin and Kapur32} there needs to be an increased emphasis on improving mental health of young people in relevant settings, such as schools. ^{Reference Wasserman, Hoven, Wasserman, Wall, Eisenberg and Hadlaczky37} Negating the perception young people have of hanging as a ‘quick and easy death’ may also help. ^{Reference Biddle, Donovan, Owen-Smith, Potokar, Longson and Hawton38}

A recent report highlights the significant gaps in local implementation of the National Suicide Prevention Strategy for England. ³⁹ It is essential that local areas have a suicide prevention action plan, a multiagency suicide prevention group and audit local suicides. ⁴⁰ In addition, the systematic method of reviewing all child deaths, as is undertaken in England and Wales, Australia, New Zealand and the USA, is an important method of identifying opportunities to prevent future child deaths. ^{Reference Fraser, Sidebotham, Frederick, Covington and Mitchell41,42}

An analysis of adolescent suicides in England between 1997 and 2003 found only 14% of those dying by suicide had contact with mental health services in the year prior to death, compared with around 26% of the adult population. ^{Reference Windfuhr, While, Hunt, Shaw, Appleby and Kapur6} Although the majority of adolescents will have experienced mental health problems prior to suicide, in excess of 20% do not. Thus, there is a need for universal mental health promotion and suicide prevention strategies at multiple levels, including that of the individual, family, school, employer, media and community.