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The New Zealand Medical Journal

 Journal of the New Zealand Medical Association, 06-June-2003, Vol 116 No 1175

Suicide in New Zealand I: time trends and epidemiology
Annette Beautrais
In recent years there has been increasing public and professional interest in the issue of suicide in New Zealand.1,2 This interest has largely been motivated by concerns about New Zealand’s high rates of youth suicide in comparison with international statistics. Despite this public interest, there have been relatively few attempts to provide accessible summary data on what is, and what is not, known about suicide in New Zealand. This is the first of two articles that attempt to address, in summary form, a series of key issues relating to suicidal behaviour.
This article examines the basic epidemiology of suicidal behaviours in New Zealand including: (a) time trends; (b) gender differences; (c) age differences; and (d) differences in terms of ethnicity. A second article will examine risk factors for suicidal behaviour and approaches to suicide prevention for young people (age <25), and for adults (age ≥25).3

Time trends in suicide, 1950–1999

Figure 1 presents overall trends in suicide rates from 1950 to 1999 derived from data provided by the New Zealand Health Information Service (NZHIS). The data represent all those deaths for which there are coroners’ verdicts of suicide.
Suicide rates for males have shown a relatively steady increase during the 50-year period. The male rate of suicide in 1999 was 18.9 deaths per 100 000, compared with 13.3 deaths per 100 000 in 1950. In contrast, the rate for females has remained relatively static: 4.6 deaths per 100 000 in 1950, and 6.4 deaths per 100 000 in 1999.
The increase in rates of male suicide is largely, but not wholly, explained by a rapid increase in rates of youth (15–24 years) suicide that occurred after 1970. This can be seen from Figure 2, which shows time trends in youth suicide for the 50-year period from 1950–1999. Rates of male youth suicide began to increase in the 1970s and then showed an abrupt increase over the period from the mid-1980s to the mid-1990s. However, in the last five years (1995–1999), the male youth suicide rate in New Zealand has declined.
In addition, during the last 15 years there has been a steady increase in the rate of female youth suicide. In 1985, females accounted for 20% of youth suicides (age 15–24). In 1999, 31% of youth suicides were female.
Figure 1. Suicide rates, total population by gender, 1950–1999 (annual age-standardized rates)

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Figure 2. Youth (15-24 years) suicide rates by gender, 1950–1999, (age-standardized rates)

Age differences in suicide rates

The comparisons in Figures 1 and 2 do not provide a comprehensive description of age differences in suicidal behaviours. Figure 3 shows age-specific rates of suicide for males and females presented in five-year intervals, for 1999. The following conclusions may be drawn from this graph:
  • Risks of suicide for males tend to increase up to age 20, remain relatively stable over the period from 20–39 years, decline to age 69, and increase thereafter. An important implication is that those who are at most risk of suicide are males aged 20–39. It is also notable that rates of suicide amongst male teenagers are less than half the rates of suicide amongst young adult males, aged 20–39.
  • Most youth suicides (following the World Health Organization (WHO) convention that ‘youth’ describes those aged 15–24) occur amongst young adult males aged 20–24, rather than amongst teenagers aged 15–19.
  • Suicide rates for females tend to increase to age 24, remain relatively high to age 45, and show a small but consistent decline thereafter. In contrast to males, rates of suicide amongst females are similar for teenagers (15–19 years) and for young adults (20–24 years).

Figure 3. Suicide rates by age and gender, New Zealand, 1999

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To place the results in Figure 3 in context, Figure 4 shows the percentages of total deaths that are attributable to suicide for each age and gender group. This Figure thus permits assessment of the extent to which suicide contributes to mortality within a given age group. It shows that, for both genders, the percentage of deaths attributable to suicide tends to increase up to ages 20–24, and then declines with increasing age. After age 60, suicide accounts for an inconsequential proportion of all deaths.
Figure 4. Percentage of total mortality accounted for by suicide, by age and gender, 1999

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Ethnicity and suicide

As a result of changes in the ways in which the ethnicity of those dying by suicide has been recorded it is not possible to examine ethnic differences in suicide rates prior to 1995.1,4 Before this time, the ethnicity of suicide was based upon an assessment of the individual’s extent of Maori descent. Recognition of the limitations of this method of measurement led to a revision of data collection methods. Since 1995, ethnicity has been defined on the basis of the family’s report of the individual’s ethnic self-identification. This change in definitions led to a clear discontinuity in time-series data, and an under-enumeration of Maori suicide prior to 1995.
Figure 5a compares Maori and non-Maori suicide rates, for all ages, during the period 1996–1999. It shows that, for both males and females, from 1996 through to 1998, Maori had higher rates of suicide than non-Maori. However, the most recent data (1999) show no difference between Maori and non-Maori suicide rates, for both males and females.
The results in Figure 5a may be elaborated by examining trends in youth (15–24 years) suicide data. These are shown in Figure 5b. The trends in Figure 5b differ from those for the total population. For both young males and females, Maori have had higher rates of suicide than non-Maori each year from 1996 to 1999. The most recent data (1999) suggest that young Maori males and females are approximately one and a half times more likely to die by suicide than non-Maori young people.
Figure 5a. Maori and non-Maori suicide rates, total population by gender, 1996–1999
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Figure 5b. Maori and non-Maori suicide rates, 15–24 years by gender, 1995–1999
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Trends in methods of suicide

The methods by which people die by suicide are of considerable policy relevance to the extent that one approach to suicide prevention is through restriction of access to particular methods. For example, it has been suggested that in the United States restriction of access to firearms could result in substantial reductions in suicide rates.5,6
In New Zealand, the commonly used methods of suicide vary with gender. For males, the most frequently used methods are hanging, vehicle exhaust gas, and firearms.7 Figure 6a shows time trends in these major methods of suicide for males of all ages for the period 1980–1999. It is evident that over the last two decades there have been substantial increases in the use of both hanging and vehicle exhaust gas, and a recent decline in the use of firearms. Currently, firearms account for only 11% of all male suicide deaths.

Figure 6a. Trends in major methods of male suicide, 1980–1999 (percentage of total suicides)

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In females, the most commonly used methods of suicide are hanging, vehicle exhaust gas and self-poisoning.7 Figure 6b shows time trends in rates of suicide for these common methods, for females of all ages, from 1980 to 1999. There have been major changes in female methods of suicide. In 1980 the leading method was self-poisoning. Over the years the use of this method has declined (with self-poisoning accounting for 8% of female suicide deaths in 1999), and there have been increases in the use of hanging and vehicle exhaust gas. The use of hanging increased five-fold from 1980 to 1999, with hanging accounting for the majority (almost 85%) of all female suicide deaths in 1999.

Figure 6b. Trends in major methods of female suicide, 1980–1999 (percentage of total suicides)

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Both Figures 6a and 6b show clear increases in suicide by hanging for both males and females. These increases are largely accounted for by an increasing use of hanging amongst young people aged 15–24. Figures 7a and 7b show time trends in the major methods of youth suicide for males and females. These figures show that, for both genders, hanging has become increasingly common, currently (1999) accounting for 65% of male, and 75% of female, youth suicides.
Figure 7a. Trends in major methods of male youth suicide, 1980–1999 (percentage of total suicides)

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Figure 7b. Trends in major methods of female youth suicide, 1980–1999 (percentage of total suicides)

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Discussion

Over the last fifty years there have been clear changes in rates of suicide, with increased rates evident for both genders and amongst younger age groups. The net result of these trends is that suicide makes a significant contribution to mortality in New Zealand and, particularly, to mortality amongst those under 35 years.
The reasons for the rapid increase in male youth suicide rates in the mid-1980s and the more recent increase in female youth suicide rates are not known. It has been suggested that these increases reflected the effects of economic restructuring on the life opportunities of young people, particularly males.8 However, this explanation is not consistent with the fact that, at an individual level, associations between economic factors and youth suicide rates tend to be relatively modest.9–12
In an examination of time trends in suicidal behaviour for the European Union, Rutter and Smith concluded that explanations for the rapid increase in youth suicide might usefully be sought in the following areas:
‘increased rates of depression; the increase in the use of alcohol and psychoactive drugs; the possible role of antisocial behaviour; the influence of suicidal models, either within the family and intimate circle, or in the mass media; the possible increase in family conflict and decline in parental support associated with changes in family structures; the possible effect of an extended period of social dependency during adolescence; and the likely role of changing circumstances in society as a whole.’13
It is likely that these same circumstances have played a role in the increase in youth suicide observed in New Zealand.
Public and policy attention in New Zealand has tended to focus upon youth suicide with tacit assumption that such suicide is predominantly teenage suicide. This misperception has led to a public view that youth suicide prevention programmes need to be school based to reach those young people most at risk of suicide. However, young people at school constitute only a minority of the population involved in youth suicide. Recent (1999) data suggest that only approximately 15% of youth suicides occurred amongst young people who were at school, with the majority (two thirds) of youth deaths occurring amongst young people aged 19 to 24 years. This suggests the need for policy emphases to shift away from adolescent populations and to pay greater attention to the needs of young adults in the age range of 20–29.
The period of highest risk for suicide for both males and females appears to be from age 20 to 45 years. The needs of this population have not been well served by current policies, which have tended to focus on youth suicide with an emphasis upon suicide amongst school-aged young people. For example, whilst policy guidelines have been developed for addressing the issue of youth suicide, there has been no corresponding investment into addressing the more prevalent problem of suicide in adults aged 20–45.
In common with other trends in mortality in New Zealand,14,15 Maori youth emerge as being at higher risk for suicide than non-Maori youth. Estimates suggest that rates of Maori youth suicide are approximately one and a half times higher than those of non-Maori. The reasons for the higher rate of suicide amongst young Maori are not clearly understood but it has been suggested that these may be due to social and cultural inequalities that make Maori particularly vulnerable to suicidal behaviours.16
A feature that pervades suicide data is the higher rates of suicide by males. This difference extends across age (Figures 1–4 above) and ethnicity (Figure 5), and has often led to the assertion that ‘suicide is a male problem’. This claim is potentially misleading. In fact, when the spectrum of suicidal behaviours in the population is examined, females emerge as being more prone to suicidal behaviour than males. For example, findings from the Christchurch Health and Development Study have suggested that females report suicidal thoughts at 1.3 times the rate of males and make suicide attempts at almost twice the rate of males.17 These trends are also evidenced in hospitalisation statistics. In 1999/2000, for example, 63% of all admissions to hospital in NZ for suicide attempts were females (www.nzhis.govt.nz).
The association between suicidal behaviour and gender is thus paradoxical. Although females show higher rates of suicidal ideation and suicide attempt, males more frequently die by suicide. The key to this gender paradox probably lies largely, if not wholly, with gender differences in choice of method for suicide attempt. As may be seen from Figures 6 and 7, traditionally there have been marked differences in male and female method choices, with females more often choosing self-poisoning and males more often choosing the more lethal methods of hanging and vehicle exhaust gas.
The extent to which gender differences in suicidal behaviours could be explained by gender-related differences in method choice has been examined in a recent paper comparing suicide attempts by young males and females.18 This analysis suggested that nearly all of the gender differences in rates of youth suicide arose from gender-related differences in method choice. The paper concluded:
‘The fact that males were more likely than females to die by suicide was completely explained by the use of more immediately lethal methods of suicide attempt by males. While the majority of males who died by suicide used hanging, vehicle exhaust gas, firearms, and jumping, the majority of serious suicide attempts by females were by self-poisoning, a method which, while it may have high toxicity, tends to have low lethality and a relatively slow rate of action.’
These findings have potentially important implications given the increasing use by females of highly lethal methods such as hanging and vehicle exhaust gas (Figure 7b). Indeed, it would appear that the recent increase in female youth suicide is largely, if not wholly, due to the increasing use of hanging as a method of suicide by young females.
The clear majority of suicides, in people of all ages, occur by hanging. The dominance of hanging, and the ubiquitous availability of the materials and opportunities for hanging, suggest that there is extremely limited potential to reduce suicide by restricting access to means of suicide. The clear policy implication of this observation is that suicide prevention in New Zealand needs to focus on a range of approaches designed to address the known risk factors for suicidal behaviour.3
Author information: Annette L Beautrais, Principal Investigator, Canterbury Suicide Project, Christchurch School of Medicine and Health Sciences, Christchurch
Correspondence: Dr A L Beautrais, Canterbury Suicide Project, Christchurch School of Medicine and Health Sciences, P O Box 4345, Christchurch. Fax: (03) 372 0405; email: suicide@chmeds.ac.nz
References:
  1. Ministry of Health. Suicide trends in New Zealand 1978–1998. Wellington: New Zealand Health Information Service; 2001.
  2. Te Puni Kokiri, Ministry of Youth Affairs, Ministry of Health. New Zealand Youth Suicide Prevention Strategy: In Our Hands/Kia Piki te Ora o te Taitamariki. Wellington: Te Puni Kokiri, Ministry of Youth Affairs, Ministry of Health; 1998.
  3. Beautrais AL. Suicide in New Zealand II: a review of risk factors and prevention. NZ Med J 2003;116(1175): URL: XXXX
  4. Statistics New Zealand. Demographic trends. Wellington: Statistics New Zealand; 1998.
  5. Brent DA. Firearms and suicide. Ann N Y Acad Sci 2001;932:225–39.
  6. Lambert MT, Silva PS. An update on the impact of gun control legislation on suicide. Psychiatr Q 1998;69:127–34.
  7. Beautrais AL. Methods of suicide in New Zealand 1977-1996. Wellington: Ministry of Health; 1999.
  8. Hassall I. Why are so many young people killing themselves? Butterworths Family Law Journal 1997;2:153–8.
  9. Beautrais AL, Joyce PR, Mulder RT. Unemployment and serious suicide attempts. Psychol Med 1998;28:209–18.
  10. Blakely T. The New Zealand Census-Mortality Study. Socioeconomic inequities and adult mortality 1991–1994. Wellington: Ministry of Health; 2002.
  11. Fergusson DM, Horwood LJ, Lynskey MT. The effects of unemployment on psychiatric illness during young adulthood. Psychol Med 1997;27:371–81.
  12. Fergusson DM, Horwood LJ, Woodward LJ. Unemployment and psychosocial adjustment in young adults: causation or selection? Soc Sci Med 2001;53:305–20.
  13. Rutter M, Smith DJ. Psychosocial disorders in young people: time trends and their causes. Chichester: John Wiley & Sons Ltd; 1995.
  14. Pomare E, Keefe-Ormsby V, Ormsby C, et al. Hauora: Maori standards of health III – a study of the years 1970–1991. Wellington: Wellington School of Medicine; 1995.
  15. Public Health Centre. Progress on health outcome targets: the state of the public health in New Zealand. Wellington: Public Health Commission; 1995.
  16. Te Aho Lawson K. Kia Piki te Ora o te Taitamariki: a review of evidence. Wellington: Te Puni Kokiri; 1998.
  17. Fergusson DM, Woodward LJ, Horwood LJ. Risk factors and life processes associated with the onset of suicidal behaviour during adolescence and early adulthood. Psychol Med 2000;30:23–39.
  18. Beautrais AL. Suicide and serious suicide attempts in young people: a multiple group case control study. Am J Psychiatry. In press 2003.


     
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