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Comparison of suicide rates and methods in English, Scots and Irish migrants in Australia
Soc. Sci. Med. Vol. 17. No. 11. pp. 705-708+ 1983
0277-9536/83/110705-04503.00/0 Pergamon Press Ltd
Printed in Great Britain
C O M P A R I S O N OF SUICIDE RATES A N D M E T H O D S IN ENGLISH, SCOTS A N D IRISH MIGRANTS IN AUSTRALIA P. W. BURVILL, M. G. McCALL, T. WOODINGSand N. S. STENHOUSE The University of Western Australia, Department of Psychiatry and Behavioural Science, 10 Murray Street (Kirkman House, 1st Floor), Perth, Western Australia 6000, Australia Abstract~A comparison was made of the suicide rates and methods for the period 1962-1971 of
migrants in Australia from England and Wales, Scotland and Ireland with those in their country of origin. Suicide rates for all three migrant groups were very similar to each other, although greater than in their country of origin especially those for Eire. The data suggest that the official lower rates in Scotland compared with England and Wales are due to ascertainment differences. Similar conclusions were drawn regarding the official rates in Eire. Several hypotheses were raised regarding the influence of religion on suicide rates in Eire, Northern Ireland and Australia.
Scotland has always had a lower suicide rate than England and Wales [1]. This phenomenon has been the subject of several investigations [1-3]. The latter study refuted the possibility that the different legal systems of ascertainment of suicide was the cause of these differences, and pointed out that the differences were only in the over 65 years age group. The authors raised the possibility that differences in the amount of economic hardship and of alcoholism in the two areas might have accounted for the differences. The very low rate of suicide reported in Ireland has been critically examined by several workers [4-6]. McCarthy and Walsh [5] concluded that the discrepancy between official and 'true' suicide rates In Ireland was greater than in Scotland and in England and Wales, as religious and social attitudes tended to make coroners reluctant to return a suicide verdict. Barraclough [6] showed that for 1968-1970, although the English official suicide rates were four times greater than Eire's, England's undetermined and accident rates were substantially less. By combining the suicide and undetermined rates, which he claimed was probably the best statistic with which to compare two countries suspected of having different suicide definitions, Barraclough showed that the incidence of suicide in England was twice that of Eire. A study of the suicide rates in immigrants from England and Wales, Scotland and Ireland, affords an opportunity to establish whether the reported differences in suicide rates in the three countries of origin applies also to immigrants in Australia from those areas. Any bias caused by differences in ascertainment procedures in the countries of origin would be unlikely to apply to the three migrant groups in Australia. This paper reports the results of such a study based on suicides in Australia for the years 1961-'1970. METHODS
These results were based on data for all deaths in Australia occurring in the 10 years 1962-1971, which were made available by the courtesy of the Australian Bureau of Statistics. Details of these data for the 5
years 1962-1966 have been described by Stenhouse and McCall [7]. All rates quoted are per 100,000 total population. In the calculation of rates the numerator is the number of suicides occurring, in the 10 year period 1962-1971, which was derived from the addition of I.C.D. codes E971-979 (7th Edition) for the 6 years 1962-1968 and E950-959 (8th Edition) for the 4 years 1969-1971. The denominator for each specific category of country of birth was the number of such persons living in Australia during the 10 year period 1962-1971. This was estimated from quinquennial census data for 1961, 1966 ~ind 1971 by fitting a curve through these three points and then 'integrating' from 1962 to 1971 inclusive. Variable groupings of age above 69 years in each of the three censi years necessitated the use of a 70 plus age category. Age standardised rates were calculated using the direct method described by Hill [8]. The standard population was the Australian born population aged 15 years and over calculated for the years 1962-1971 as described above for the denominator. All rates quoted for Ireland related to the whole of Ireland as the majority of Irish born migrants in Australia did not differentiate between Northern Ireland and Eire when specifying their country of birth in the census data. In the calculation of the ratio of active:passive methods of suicide, active methods are those classified under I.C.D. codes E974-978 (7th Edition) and E953-957 (8th Edition), viz. hanging, strangulation and suffocation; drowning; firearms and explosives; cutting and piercing instruments; and jumping from a high place. Passive methods are I.C.D. Codes E971-973 (7th Edition) and E950-952 (8th Edition) viz. poisoning by solid and liquid substances; poisoning by domestic gas; and poisoning by other gases. RESULTS
Table 1 outlines for each of the three migrant groups during the period 1961-1970 their population in Australia, the age standardised suicide rate and the suicide rate in the respective country of origin during the years 1960o1969. In both sexes the WHO published suicide rates (column b) were greater for
705
P. W. BURVILLet al.
706
Table 1. Suicide rates of migrants in Australia and in their country of origin Country ' of birth England and Wales Scotland Ireland Australia
Population in Australia (000's) M F
Number of suicides M F
Suicide rates in Australia* (a) M F
Suicide rates in Country of Birth (b) M F
Ratio (a) : /bt M F 1.4 1.8 2.6 5.2
374 78 31
348 73 25
911 220 91
430 110 29
17.0 17.3 17.7
9.0 10.1 7.6
12.1 9.7 6.6t 3.4t
8.4 6.1 3.5 1.2
4700
4979
7632
4174
16.3
8.8
16.3
8.8
1.1 1.6 2.2 6.3
*Age standardised on Australian born population. tNorthern Ireiand. .+Eire.
England and Wales than for Scotland; the rates for Northern Ireland were only a half, and for Eire one quater (male) to one-fifth (female) those for England and Wales. For males the suicide rates for all three migrant groups were approximately the same, and slightly higher than that for the Australian born. For females the rates for the migrants from England and Wales and from Scotland were slightly higher, and for the Irish migrants slightly lower, than for the Australian born. Of the four population groups, rates for the Irish migrants were the highest of all the male rates, and lowest of the female rates, although in each case these age standardised rates for the Irish were based on small numbers. The suicide rates for each of the migrant groups were all greater than in their country of origin. The latter difference was greatest for the Irish, their migrant rates being over two-fold that for Northern Ireland, and over fivefold that for Eire, whereas the differential for the English and Welsh, and the Scots immigrants varied from 1.1 to 1.8. The age--sex specific rates were essentially the same for all three migrant groups. Methods of suicide
Table 2 (a) and (b) outlines the individual suicide methods used by the Australian born and the three migrant groups, and "those used in their country of origin. These methods are grouped into passive and active methods. The data quoted for Ireland apply to Eire only and are the average for the 2 years 1968-1969, derived from Brooke i-9]. Unfortunately official WHO data on methods of suicide for either Eire or Northern Ireland, comparable with the other two ethnic groups, were not available. In the males the Irish migrants used more active methods than either of the other two migrant groups, with the Australian born occupying an intermediate position between the former and the latter. The Irish migrants used a lower proportion of both domestic and other gas, and a higher proportion of cutting instruments and firearms. The proportion of poisoning was very similar in all migrant groups and the Australian born. The major difference from the Australian born was the lower proportion of the use of firearms in all three migrant groups, although these were much higher than in their country of origin. There were only minor differences in the distribution of suicide methods in Scotland and in England and Wales, but major differences between these and those
in Eire. The latter had a very high proportion of active methods, especially hanging, a low proportion of poisoning and no recorded use of domestic or other gas. Thus the methods used by the Irish migrants were much more akin to both the Australian born and the other two migrant groups, than they were to those used in Eire. In females, there were some differences in the distribution of methods used by the English and Welsh, and the Scots, both in their own country and in Australia. These differences were relatively minor, except that the migrants from both countries had a greater proportion of poisoning and a smaller proportion of domestic gas. In the latter the migrants were more akin to the Australian born. The major differences were in the Irish, both at home and in Australia, especially the former. The Irish had a low passive:active ratio of methods used (1.0) compared with all the other groups. A lower proportion used poisoning, and more used gas, whereas the proportion who used hanging, drowning and cutting/piercing instruments were relatively high. By contrast, the Irish migrants had the highest passive:active ratio (6.25), the highest proportion of poisoning and the lowest of drowning. The Irish, both at home and in Australia, had double the proportion of hanging than any of the other groups. Thus any differences in methods used by the three migrant groups in Australia in both sexes were most marked in the Irish. DISCUSSION
For all three migrant groups the suicide rates were greater than the published figures for their country of origin, a common finding in such studies [10-12]. However the margin of difference for the Irish was excessive. The similarity of rates for the migrants from Scotland and from England and Wales lends weight to the hypothesis [2] that different methods of ascertainment, rather than true differences in rates [3], in those two countries is the cause of the long documented lower rates in Scotland. However, the most marked findings in this study pertain to the Irish migrants, especially the big difference in their suicide rates compared with Eire, and even compared with the larger rate calculated by Barraclough [6] for Eire by summing the suicide and undetermined rates. These data raise a number of questions, to which there are no conclusive answers. Firstly, are the sui-
707
Suicide comparison rates and methods Table 2(a). Suicide methods of male migrants in Australia and in their country of origin* (percentages) England and Wales
Scotland
Ireland
Australian born 01 = 7480)
Migrant In = 883)
E. & W.
Migrant (n = 215)
Scot.
Migrant In = 90)
Irel.*
Poisoning Domestic gas Other gas
31.1 7.3 9.6
33.9 10.9 12.1
24.8 38.0 5.0
32.1 15.8 10.2
23.2 36.8 2.1
35.6 5.6 2.2
20.7 ---
Method of suicide
Passive
48.0
56.9
67.8
58.1
62.1
43.3
20.7
Hanging Drowning Firearms Jumping •Cutting
10.8 3.2 34.4 2.1 1.5
11.1 4.2 22.9 3.5 1.4
15.7 7.4 5.8 3.3 --
13.0 5. I 17.7 3.3 2.8
6.6 9.2 -1.3 --
13.3 5.6 26.7 4.4 6.7
43.1 12.1 10.3 5.2 8.6
Active
52.0
43.1
32.2
41.9
37.9
56.7
79.3
Total
100.0
100.0
100.0
100.0
100.0
100.0
100.0
Passive:active
0.92
1.32
2. I I
1.39
1.64
0.76
0.26
*Does not include other, miscellaneous methods. taverage of methods in Eire 1968-1969. Table 2(bL Suicide methods of female migrants in Australia and their country of origin Ipercentagesl England and Wales
Scotland
Ireland
Australian born 07 = 4091)
Migrant 07 = 421)
E. & W.
Migrant tn = 106)
Scot.
Migrant (n = 29)
Irel.*
Poisoning Domestic gas Other gas
66.6 11.1 1.8
70.5 13.3 1.2
39.5 42.1 1.3
65.1 15. I 0.9
50.8 29.8 --
75.9 10.3 --
50.0 ---
Passive
79.5
85.0
82.9
81.1
80.6
86.2
50.0
6.5 5.7 5.4 1.0 1.9
5.0 6.0 2.1 -1.9
6.6 9.2 -1.3 --
3.8 11.3 1.9 -1.9
5.3 12.3 -1.8 --
10.4 3.4 ----
11.1 16.6 5.6 5.6 11.1
20.5
15.0
17.1
18.9
19.4
13.8
50.0
i 00.0
100.0
100.0
100.0
100.0
100.0
100.0
Method of suicide
Hanging Drowning Firearms Jumping Cutting Active Total Passive:active
3.87
5.67
4.85
4.29
4.16
6.25
1.0
*Average of methods in Eire 1968-1969.
cide rates really lower in Eire? M c C a r t h y and Walsh ['51 made their own estimates of the 'true' rates but these were still only one-quarter that of England and Wales. However the similarity of the rates of the Irish, Scots and English migrants in Australia c o m p a r e d with the differential rates in their countries of origin, is against the findings of Sainsbury and Barraclough [10"1 for migrants in America and of Burvill et al. [11, 121 for Australia. The latter studies showed that the rank ordering of the suicide rates of the various migrant groups correlated highly with that of the rates in their country of origin. Thus we would expect to find low Irish migrant rates in Australia. Yet in this study they are of the same order as the English and Scots migrants. It is difficult not ~o conclude that the official Irish suicide rates are artificially low. A possible alternative is that religious influences operating in Eire do result in low suicide rates, but that t h e s e influences cease to operate in migrants from Eire in Australia. The general impression in Australia is that S,S.M, [7 [ I - - B
the great majority of Irish migrants are either from Eire, or are Catholics from N o r t h e r n Ireland. Such an explanation would go against the proposals of Burvill et al. [12] of powerful sociological factors, including those of religion, influencing suicide rates both in the country of origin and in Australia for all other migrant groups. The official suicide rates for N o r t h e r n Ireland are half for males, and in females less than half, that of the English rates. These low rates in N o r t h e r n Ireland appear not to have attracted much attention in the literature c o m p a r e d with the low rate from Eire. There are several possible explanations. Firstly, that suicide rates in N o r t h e r n Ireland are of the same order as those in Scotland and in England and Wales, but that the ascertainment procedures are so considerably different in N o r t h e r n Ireland as to give official rates of only one half those of the other two 'countries'. To date n o b o d y has seriously raised the latter possibility, although its investigation seems
708
P. W. BURVILLet aL
warranted. The second is that Catholics, whether in Eire or Northern Ireland, really do have low suicide rates, and that the official low suicide rates in the latter country are influenced by its large Catholic population. If the second explanation is true, this factor combined with findings presented in this study, raises the hypotheses that the effects of Catholic influences in both Eire and Northern Ireland really do result in a low suicide rate in those countries, but that these influences are not as enduring in migrants from these countries as are the sociological influences in migrants from other countries [12]. Such a hypothesis would not exclude the possibility of an additional official ascertainment factor operating in Eire resulting in abnormally low official suicide rates. The most marked feature of the suicide methods in Eire, in 1968-1969, quoted by Brooke [9], is the very low proportion of passive methods, especially the absence of any recorded suicides by domestic or by other gas in either sex. Both poisoning and use of gas are methods which are likely to be classified as accidental rather than suicide 1-13], or after the introduction of I.C.D. 8 in 1968, to be classified as 'undetermined'. Many workers think that most of the male deaths attributed to accidental poisoning are in fact suicides, and the Standing Medical Committee of the United Kindom went further in saying that most grown up people who swallow dangerous drugs do so intentionally [9]. Data given by Brooke I-9] and McCarthy and Walsh 1-5] for Eire, combined with that from Burvill et al. 1-14] for Australia, indicate that the ratio of suicides to combined accidental and undetermined deaths is much higher in Australia than in Eire, especially that relating to poisoning. It is possible that true suicide rates for Eire are derived not from combining suicide and undetermined deaths as advocated by Barraclough 1-6], but by combining all suicides and undetermined deaths with accidental deaths from overdosage and possibly also those from domestic and other gases. CONCLUSIONS The data support the hypothesis that the documented lower suicide rates in Scotland compared with England and Wales are due to differences in ascertainment. Although it seems very likely that ascertainment methods in Eire also contribute a great deal to the very low official suicide rates in that country, the findings suggest that the suicidal behaviour of the Irish both in their own country and in Australia is
different to that of the English and Scots. However these differences are nowhere near as great as suggested by the official statistics for Eire. Consideration of the findings has generated several other hypotheses, which cannot be answered by the available data, but warrant further investigation. Acknowledgement--The authors wish to acknowledge a grant from the N.H. and M.R.C. to conduct this study.
REFERENCES
1. Ross O. and Kreitman N. A further investigation of differences in suicide rates of England and Wales and Scotland. Br. J. Psychiat. 127, 575, 1975. 2. Barraclough B. M. Are the Scottish and English suicide rates really different? Br. J, Psychiat. 120, 267, 1972. 3. Kreitman N. Suicide in Scotland in comparison with England and Wales. Br. J. Psychiat. 120, 83, 1972. 4. McCarthy P. D. and Walsh D. Suicide in Dublin. Br. reed. J. i, 1393, 1966. 5. McCarthy P. D. and Walsh D. Suicide in Dublin: !. The under reporting of suicide and the consequences for national statistics, Br. J. Psychiat. 126, 301. 1975. 6. Barraclough B. M. The different incidence of suicide in Eire and England and Wales. Br. J. Psychiat. 132, 36. 1978. 7. Stenhouse N. S. and McCall M. G. Differential mortality from cardiovascular disease in migrants from England and Wales, Scotland and Italy and nativeborn Australians. J. chron. Dis. 23, 423, 1970. 8. Hill A. B. Principles of Medical Statistics, 9th Edition. The Lancet Ltd, London, 1971. 9. Brooke E. M. Suicide and Attempted Suicide. Public Health Papers No. 58. World Health Organization, Geneva, 1974. 10. Sainsbury P. and Barraclough B. Differences between suicide rates. Nature 220, 1252, 1968. 11. Burvill P. W., McCall M. G., Stenhouse N. S. and Reid T. A. Deaths from suicide, motor vehicle accidents and all forms of violent death among migrants in Australia, 1962-66. Acta psychiat, scand. 49, 28, 1973. 12. Burvill P. W., Woodings T. L., Stenhouse N. S. and McCall M. G. Suicide during 1961-70 of migrants in Australia. Psychol. Med. 12, 295, 1982. 13. Oliver R. G. Comments on the differences in rates of reported suicide between States of Australia. Mimeo, Department of Social and Preventive Medicine, Monash University, 1971. 14. Burvill P. W., McCall M. G., Stenhouse N. S. and Woodings T. L. The relationship between suicide, undetermined deaths and accidental deaths in the Australian born and migrants in Australia. Aust. N.Z.JI Psychiat. 16, 179, 1982.
0277-9536/83/110705-04503.00/0 Pergamon Press Ltd
Printed in Great Britain
C O M P A R I S O N OF SUICIDE RATES A N D M E T H O D S IN ENGLISH, SCOTS A N D IRISH MIGRANTS IN AUSTRALIA P. W. BURVILL, M. G. McCALL, T. WOODINGSand N. S. STENHOUSE The University of Western Australia, Department of Psychiatry and Behavioural Science, 10 Murray Street (Kirkman House, 1st Floor), Perth, Western Australia 6000, Australia Abstract~A comparison was made of the suicide rates and methods for the period 1962-1971 of
migrants in Australia from England and Wales, Scotland and Ireland with those in their country of origin. Suicide rates for all three migrant groups were very similar to each other, although greater than in their country of origin especially those for Eire. The data suggest that the official lower rates in Scotland compared with England and Wales are due to ascertainment differences. Similar conclusions were drawn regarding the official rates in Eire. Several hypotheses were raised regarding the influence of religion on suicide rates in Eire, Northern Ireland and Australia.
Scotland has always had a lower suicide rate than England and Wales [1]. This phenomenon has been the subject of several investigations [1-3]. The latter study refuted the possibility that the different legal systems of ascertainment of suicide was the cause of these differences, and pointed out that the differences were only in the over 65 years age group. The authors raised the possibility that differences in the amount of economic hardship and of alcoholism in the two areas might have accounted for the differences. The very low rate of suicide reported in Ireland has been critically examined by several workers [4-6]. McCarthy and Walsh [5] concluded that the discrepancy between official and 'true' suicide rates In Ireland was greater than in Scotland and in England and Wales, as religious and social attitudes tended to make coroners reluctant to return a suicide verdict. Barraclough [6] showed that for 1968-1970, although the English official suicide rates were four times greater than Eire's, England's undetermined and accident rates were substantially less. By combining the suicide and undetermined rates, which he claimed was probably the best statistic with which to compare two countries suspected of having different suicide definitions, Barraclough showed that the incidence of suicide in England was twice that of Eire. A study of the suicide rates in immigrants from England and Wales, Scotland and Ireland, affords an opportunity to establish whether the reported differences in suicide rates in the three countries of origin applies also to immigrants in Australia from those areas. Any bias caused by differences in ascertainment procedures in the countries of origin would be unlikely to apply to the three migrant groups in Australia. This paper reports the results of such a study based on suicides in Australia for the years 1961-'1970. METHODS
These results were based on data for all deaths in Australia occurring in the 10 years 1962-1971, which were made available by the courtesy of the Australian Bureau of Statistics. Details of these data for the 5
years 1962-1966 have been described by Stenhouse and McCall [7]. All rates quoted are per 100,000 total population. In the calculation of rates the numerator is the number of suicides occurring, in the 10 year period 1962-1971, which was derived from the addition of I.C.D. codes E971-979 (7th Edition) for the 6 years 1962-1968 and E950-959 (8th Edition) for the 4 years 1969-1971. The denominator for each specific category of country of birth was the number of such persons living in Australia during the 10 year period 1962-1971. This was estimated from quinquennial census data for 1961, 1966 ~ind 1971 by fitting a curve through these three points and then 'integrating' from 1962 to 1971 inclusive. Variable groupings of age above 69 years in each of the three censi years necessitated the use of a 70 plus age category. Age standardised rates were calculated using the direct method described by Hill [8]. The standard population was the Australian born population aged 15 years and over calculated for the years 1962-1971 as described above for the denominator. All rates quoted for Ireland related to the whole of Ireland as the majority of Irish born migrants in Australia did not differentiate between Northern Ireland and Eire when specifying their country of birth in the census data. In the calculation of the ratio of active:passive methods of suicide, active methods are those classified under I.C.D. codes E974-978 (7th Edition) and E953-957 (8th Edition), viz. hanging, strangulation and suffocation; drowning; firearms and explosives; cutting and piercing instruments; and jumping from a high place. Passive methods are I.C.D. Codes E971-973 (7th Edition) and E950-952 (8th Edition) viz. poisoning by solid and liquid substances; poisoning by domestic gas; and poisoning by other gases. RESULTS
Table 1 outlines for each of the three migrant groups during the period 1961-1970 their population in Australia, the age standardised suicide rate and the suicide rate in the respective country of origin during the years 1960o1969. In both sexes the WHO published suicide rates (column b) were greater for
705
P. W. BURVILLet al.
706
Table 1. Suicide rates of migrants in Australia and in their country of origin Country ' of birth England and Wales Scotland Ireland Australia
Population in Australia (000's) M F
Number of suicides M F
Suicide rates in Australia* (a) M F
Suicide rates in Country of Birth (b) M F
Ratio (a) : /bt M F 1.4 1.8 2.6 5.2
374 78 31
348 73 25
911 220 91
430 110 29
17.0 17.3 17.7
9.0 10.1 7.6
12.1 9.7 6.6t 3.4t
8.4 6.1 3.5 1.2
4700
4979
7632
4174
16.3
8.8
16.3
8.8
1.1 1.6 2.2 6.3
*Age standardised on Australian born population. tNorthern Ireiand. .+Eire.
England and Wales than for Scotland; the rates for Northern Ireland were only a half, and for Eire one quater (male) to one-fifth (female) those for England and Wales. For males the suicide rates for all three migrant groups were approximately the same, and slightly higher than that for the Australian born. For females the rates for the migrants from England and Wales and from Scotland were slightly higher, and for the Irish migrants slightly lower, than for the Australian born. Of the four population groups, rates for the Irish migrants were the highest of all the male rates, and lowest of the female rates, although in each case these age standardised rates for the Irish were based on small numbers. The suicide rates for each of the migrant groups were all greater than in their country of origin. The latter difference was greatest for the Irish, their migrant rates being over two-fold that for Northern Ireland, and over fivefold that for Eire, whereas the differential for the English and Welsh, and the Scots immigrants varied from 1.1 to 1.8. The age--sex specific rates were essentially the same for all three migrant groups. Methods of suicide
Table 2 (a) and (b) outlines the individual suicide methods used by the Australian born and the three migrant groups, and "those used in their country of origin. These methods are grouped into passive and active methods. The data quoted for Ireland apply to Eire only and are the average for the 2 years 1968-1969, derived from Brooke i-9]. Unfortunately official WHO data on methods of suicide for either Eire or Northern Ireland, comparable with the other two ethnic groups, were not available. In the males the Irish migrants used more active methods than either of the other two migrant groups, with the Australian born occupying an intermediate position between the former and the latter. The Irish migrants used a lower proportion of both domestic and other gas, and a higher proportion of cutting instruments and firearms. The proportion of poisoning was very similar in all migrant groups and the Australian born. The major difference from the Australian born was the lower proportion of the use of firearms in all three migrant groups, although these were much higher than in their country of origin. There were only minor differences in the distribution of suicide methods in Scotland and in England and Wales, but major differences between these and those
in Eire. The latter had a very high proportion of active methods, especially hanging, a low proportion of poisoning and no recorded use of domestic or other gas. Thus the methods used by the Irish migrants were much more akin to both the Australian born and the other two migrant groups, than they were to those used in Eire. In females, there were some differences in the distribution of methods used by the English and Welsh, and the Scots, both in their own country and in Australia. These differences were relatively minor, except that the migrants from both countries had a greater proportion of poisoning and a smaller proportion of domestic gas. In the latter the migrants were more akin to the Australian born. The major differences were in the Irish, both at home and in Australia, especially the former. The Irish had a low passive:active ratio of methods used (1.0) compared with all the other groups. A lower proportion used poisoning, and more used gas, whereas the proportion who used hanging, drowning and cutting/piercing instruments were relatively high. By contrast, the Irish migrants had the highest passive:active ratio (6.25), the highest proportion of poisoning and the lowest of drowning. The Irish, both at home and in Australia, had double the proportion of hanging than any of the other groups. Thus any differences in methods used by the three migrant groups in Australia in both sexes were most marked in the Irish. DISCUSSION
For all three migrant groups the suicide rates were greater than the published figures for their country of origin, a common finding in such studies [10-12]. However the margin of difference for the Irish was excessive. The similarity of rates for the migrants from Scotland and from England and Wales lends weight to the hypothesis [2] that different methods of ascertainment, rather than true differences in rates [3], in those two countries is the cause of the long documented lower rates in Scotland. However, the most marked findings in this study pertain to the Irish migrants, especially the big difference in their suicide rates compared with Eire, and even compared with the larger rate calculated by Barraclough [6] for Eire by summing the suicide and undetermined rates. These data raise a number of questions, to which there are no conclusive answers. Firstly, are the sui-
707
Suicide comparison rates and methods Table 2(a). Suicide methods of male migrants in Australia and in their country of origin* (percentages) England and Wales
Scotland
Ireland
Australian born 01 = 7480)
Migrant In = 883)
E. & W.
Migrant (n = 215)
Scot.
Migrant In = 90)
Irel.*
Poisoning Domestic gas Other gas
31.1 7.3 9.6
33.9 10.9 12.1
24.8 38.0 5.0
32.1 15.8 10.2
23.2 36.8 2.1
35.6 5.6 2.2
20.7 ---
Method of suicide
Passive
48.0
56.9
67.8
58.1
62.1
43.3
20.7
Hanging Drowning Firearms Jumping •Cutting
10.8 3.2 34.4 2.1 1.5
11.1 4.2 22.9 3.5 1.4
15.7 7.4 5.8 3.3 --
13.0 5. I 17.7 3.3 2.8
6.6 9.2 -1.3 --
13.3 5.6 26.7 4.4 6.7
43.1 12.1 10.3 5.2 8.6
Active
52.0
43.1
32.2
41.9
37.9
56.7
79.3
Total
100.0
100.0
100.0
100.0
100.0
100.0
100.0
Passive:active
0.92
1.32
2. I I
1.39
1.64
0.76
0.26
*Does not include other, miscellaneous methods. taverage of methods in Eire 1968-1969. Table 2(bL Suicide methods of female migrants in Australia and their country of origin Ipercentagesl England and Wales
Scotland
Ireland
Australian born 07 = 4091)
Migrant 07 = 421)
E. & W.
Migrant tn = 106)
Scot.
Migrant (n = 29)
Irel.*
Poisoning Domestic gas Other gas
66.6 11.1 1.8
70.5 13.3 1.2
39.5 42.1 1.3
65.1 15. I 0.9
50.8 29.8 --
75.9 10.3 --
50.0 ---
Passive
79.5
85.0
82.9
81.1
80.6
86.2
50.0
6.5 5.7 5.4 1.0 1.9
5.0 6.0 2.1 -1.9
6.6 9.2 -1.3 --
3.8 11.3 1.9 -1.9
5.3 12.3 -1.8 --
10.4 3.4 ----
11.1 16.6 5.6 5.6 11.1
20.5
15.0
17.1
18.9
19.4
13.8
50.0
i 00.0
100.0
100.0
100.0
100.0
100.0
100.0
Method of suicide
Hanging Drowning Firearms Jumping Cutting Active Total Passive:active
3.87
5.67
4.85
4.29
4.16
6.25
1.0
*Average of methods in Eire 1968-1969.
cide rates really lower in Eire? M c C a r t h y and Walsh ['51 made their own estimates of the 'true' rates but these were still only one-quarter that of England and Wales. However the similarity of the rates of the Irish, Scots and English migrants in Australia c o m p a r e d with the differential rates in their countries of origin, is against the findings of Sainsbury and Barraclough [10"1 for migrants in America and of Burvill et al. [11, 121 for Australia. The latter studies showed that the rank ordering of the suicide rates of the various migrant groups correlated highly with that of the rates in their country of origin. Thus we would expect to find low Irish migrant rates in Australia. Yet in this study they are of the same order as the English and Scots migrants. It is difficult not ~o conclude that the official Irish suicide rates are artificially low. A possible alternative is that religious influences operating in Eire do result in low suicide rates, but that t h e s e influences cease to operate in migrants from Eire in Australia. The general impression in Australia is that S,S.M, [7 [ I - - B
the great majority of Irish migrants are either from Eire, or are Catholics from N o r t h e r n Ireland. Such an explanation would go against the proposals of Burvill et al. [12] of powerful sociological factors, including those of religion, influencing suicide rates both in the country of origin and in Australia for all other migrant groups. The official suicide rates for N o r t h e r n Ireland are half for males, and in females less than half, that of the English rates. These low rates in N o r t h e r n Ireland appear not to have attracted much attention in the literature c o m p a r e d with the low rate from Eire. There are several possible explanations. Firstly, that suicide rates in N o r t h e r n Ireland are of the same order as those in Scotland and in England and Wales, but that the ascertainment procedures are so considerably different in N o r t h e r n Ireland as to give official rates of only one half those of the other two 'countries'. To date n o b o d y has seriously raised the latter possibility, although its investigation seems
708
P. W. BURVILLet aL
warranted. The second is that Catholics, whether in Eire or Northern Ireland, really do have low suicide rates, and that the official low suicide rates in the latter country are influenced by its large Catholic population. If the second explanation is true, this factor combined with findings presented in this study, raises the hypotheses that the effects of Catholic influences in both Eire and Northern Ireland really do result in a low suicide rate in those countries, but that these influences are not as enduring in migrants from these countries as are the sociological influences in migrants from other countries [12]. Such a hypothesis would not exclude the possibility of an additional official ascertainment factor operating in Eire resulting in abnormally low official suicide rates. The most marked feature of the suicide methods in Eire, in 1968-1969, quoted by Brooke [9], is the very low proportion of passive methods, especially the absence of any recorded suicides by domestic or by other gas in either sex. Both poisoning and use of gas are methods which are likely to be classified as accidental rather than suicide 1-13], or after the introduction of I.C.D. 8 in 1968, to be classified as 'undetermined'. Many workers think that most of the male deaths attributed to accidental poisoning are in fact suicides, and the Standing Medical Committee of the United Kindom went further in saying that most grown up people who swallow dangerous drugs do so intentionally [9]. Data given by Brooke I-9] and McCarthy and Walsh 1-5] for Eire, combined with that from Burvill et al. 1-14] for Australia, indicate that the ratio of suicides to combined accidental and undetermined deaths is much higher in Australia than in Eire, especially that relating to poisoning. It is possible that true suicide rates for Eire are derived not from combining suicide and undetermined deaths as advocated by Barraclough 1-6], but by combining all suicides and undetermined deaths with accidental deaths from overdosage and possibly also those from domestic and other gases. CONCLUSIONS The data support the hypothesis that the documented lower suicide rates in Scotland compared with England and Wales are due to differences in ascertainment. Although it seems very likely that ascertainment methods in Eire also contribute a great deal to the very low official suicide rates in that country, the findings suggest that the suicidal behaviour of the Irish both in their own country and in Australia is
different to that of the English and Scots. However these differences are nowhere near as great as suggested by the official statistics for Eire. Consideration of the findings has generated several other hypotheses, which cannot be answered by the available data, but warrant further investigation. Acknowledgement--The authors wish to acknowledge a grant from the N.H. and M.R.C. to conduct this study.
REFERENCES
1. Ross O. and Kreitman N. A further investigation of differences in suicide rates of England and Wales and Scotland. Br. J. Psychiat. 127, 575, 1975. 2. Barraclough B. M. Are the Scottish and English suicide rates really different? Br. J, Psychiat. 120, 267, 1972. 3. Kreitman N. Suicide in Scotland in comparison with England and Wales. Br. J. Psychiat. 120, 83, 1972. 4. McCarthy P. D. and Walsh D. Suicide in Dublin. Br. reed. J. i, 1393, 1966. 5. McCarthy P. D. and Walsh D. Suicide in Dublin: !. The under reporting of suicide and the consequences for national statistics, Br. J. Psychiat. 126, 301. 1975. 6. Barraclough B. M. The different incidence of suicide in Eire and England and Wales. Br. J. Psychiat. 132, 36. 1978. 7. Stenhouse N. S. and McCall M. G. Differential mortality from cardiovascular disease in migrants from England and Wales, Scotland and Italy and nativeborn Australians. J. chron. Dis. 23, 423, 1970. 8. Hill A. B. Principles of Medical Statistics, 9th Edition. The Lancet Ltd, London, 1971. 9. Brooke E. M. Suicide and Attempted Suicide. Public Health Papers No. 58. World Health Organization, Geneva, 1974. 10. Sainsbury P. and Barraclough B. Differences between suicide rates. Nature 220, 1252, 1968. 11. Burvill P. W., McCall M. G., Stenhouse N. S. and Reid T. A. Deaths from suicide, motor vehicle accidents and all forms of violent death among migrants in Australia, 1962-66. Acta psychiat, scand. 49, 28, 1973. 12. Burvill P. W., Woodings T. L., Stenhouse N. S. and McCall M. G. Suicide during 1961-70 of migrants in Australia. Psychol. Med. 12, 295, 1982. 13. Oliver R. G. Comments on the differences in rates of reported suicide between States of Australia. Mimeo, Department of Social and Preventive Medicine, Monash University, 1971. 14. Burvill P. W., McCall M. G., Stenhouse N. S. and Woodings T. L. The relationship between suicide, undetermined deaths and accidental deaths in the Australian born and migrants in Australia. Aust. N.Z.JI Psychiat. 16, 179, 1982.