Hostname: page-component-7c8c6479df-27gpq Total loading time: 0 Render date: 2024-03-28T03:14:08.549Z Has data issue: false hasContentIssue false

Authors' reply

Published online by Cambridge University Press:  02 January 2018

H. Tómasson
Affiliation:
Faculty of Economics and Business Administration, University of Iceland
T. Helgason*
Affiliation:
Faculty of Medicine, University of Iceland
T. Zoëga
Affiliation:
National University Hospital, Reykjavik, Iceland
*
4 Midleiti, IS-103 Reykjavik, Iceland. E-mail: tomashe@isholf.is
Rights & Permissions [Opens in a new window]

Abstract

Type
Columns
Copyright
Copyright © 2005 The Royal College of Psychiatrists 

We have data on the suicide rates by gender from 1978 to 2000. The average rate for that period is about 19 per 100 000 for men and about 5 for women. The yearly data series for women is a sequence of numbers varying from 3 to 14. Because of the small number of female suicides they can vary considerably. Even 5-year averages would have large standard deviations. If an over-dispersion coefficient of 2 is assumed, the size of the standard deviation in 5-year averages should be around 1.4 for women and 2.6 for men. Therefore, observed 5-year averages of 4–7 for women and 17–22 for men could be expected. Average rates may vary according to choice of 5-year periods (Fig. 1). The rates during 1995–1999 were 18.1 for men and 4.6 for women, but 21 for men and 5 for women during 1996–2000. The rates quoted in Isacsson's letter for 1995–1999 are actually for 1995–1996 (Reference Levi, La Vecchia and LucchiniLevi et al, 2003) and too low. Taking 5-year averages is a waste of information because it ignores the time series structure in the data. With such limited data as the number of suicides in Iceland it is vital to use statistical techniques that use data as efficiently as possible. In this case the dynamics of suicide rates seemed to be similar for both genders, so data on them was pooled. In our opinion time series methods should be used for these data as they take advantage of the time series structure of the data. Furthermore, a time series approach leads to improved P values and decreases the possibility of spurious regression (Reference Granger and NewboldGranger & Newbold, 1974).

Fig. 1 Observed suicide rates in Iceland per 100 000 by gender.

In our paper (Reference Helgason, Tomasson and ZoëgaHelgason et al, 2004a ) we mentioned that suicide rates had not decreased in Norway since 1995 in spite of increasing antidepressant sales.

In 1989 the amount of antidepressants prescribed was 13.9 defined daily doses per 1000 per day for men and 27.6 for women aged ≥15 years (Reference Helgason, Björnsson and ZoëgaHelgason et al, 1997). The amount prescribed in 2001 had increased to 66.8 and 119.1 defined daily doses per 1000 per day for men and women, respectively (Reference Helgason, Tomasson and SigfússonHelgason et al, 2004b ), i.e. a slightly greater increase for men without affecting suicide rates for either gender.

Footnotes

EDITED BY KHALIDA ISMAIL

References

Granger, C.W. J. & Newbold, P. (1974) Spurious regression in econometrics. Journal of Econometrics, 2, 111120.CrossRefGoogle Scholar
Helgason, T., Björnsson, J. K., Zoëga, T., et al (1997) Psychopharmacoepidemiology in Iceland: effects of regulations and new medications. European Archives of Psychiatry and Clinical Neurosciences, 247, 9399.CrossRefGoogle ScholarPubMed
Helgason, T., Tomasson, K. & Zoëga, T. (2004a) Antidepressants and public health in Iceland: time series analysis of national data. British Journal of Psychiatry, 184, 157162.CrossRefGoogle Scholar
Helgason, T., Tomasson, K., Sigfússon, E., et al (2004b) Screening for mental disorders in the community 1984 and 2002 and prescriptions for psychopharmaca in 1984 and 2001. LæknablaÐiÐ (Icelandic Medical Journal), 90, 553559.Google ScholarPubMed
Levi, F., La Vecchia, C., Lucchini, F., et al (2003) Trends in mortality from suicide, 1965–99. Acta Psychiatrica Scandinavica, 108, 341349.CrossRefGoogle ScholarPubMed
Figure 0

Fig. 1 Observed suicide rates in Iceland per 100 000 by gender.

Submit a response

eLetters

No eLetters have been published for this article.