KD-G Consulting, Hosle, Norway
Department of Social Medicine, University of Bristol, Bristol, UK
Correspondence: Svein Reseland, Hosletoppen 56, 1362 Hosle, Norway. Tel/fax: +47 6714 5899; e-mail: sreselan{at}online.no
Declaration of interest D.G. was a member of the Medicines and Healthcare products Regulatory Agency Expert Working Group on the Safety of SSRIs. He Working Group on the Safety of SSRIs. He was an independent advisor, receiving expenses and an attendance fee.
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Aims To investigate the relationship between antidepressant sales and trends in suicide rates.
Method Graphical and quantitative assessment of trends in suicide and antidepressant sales in Norway, Sweden, Denmark and Finland.
Results Suicide rates declined in all four countries during the 1990s, whereas antidepressant sales increased by 3- to 4-fold. Decreasing suicide rates in Sweden and Denmark preceded the rise in antidepressant sales by over 10 years, although the reductions accelerated between 1988 and 1990. In Norway, a modest but short-lived decline in suicide rates began around the time of the increase in antidepressant sales. In Finland, decreases in male suicide rates and to a lesser extent in female suicide rates began around the time of increased antidepressant sales. In all four countries decreases in suicide rates appeared to precede the widespread use of SSRIs.
Conclusions We found mixed evidence that increases in antidepressant sales have coincided with a reduction in the number of suicides in Nordic countries.
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The data on suicide rates for Norway and Sweden were available up to 2002, the data for Denmark were available up to 2000 and the data for Finland were available up to 2003. We were also able to obtain age-specific suicide trend data for Sweden and Norway. Antidepressant sales data, expressed in terms of defined daily doses (DDDs) for SSRIs and other antidepressants, were available up to 2003 for all four countries. Data on total antidepressant and SSRI prescribing were available from 1974 and 1990 respectively for Norway, from 1977 and 1991 respectively for Sweden, from 1990 for both for Denmark and from 1985 and 1989 respectively for Finland.
We plotted separate graphs for each of the four countries to enable us to compare the time trends in levels of antidepressant prescribing with the trends in overall and gender-specific suicide rates. For Norway and Sweden we also plotted age- and gender-specific suicide rates for three age groups (1524, 2544 and >45 years), as data from other countries suggest that time trends in suicide rates vary with age (Cantor, 2000).
To estimate the years (with 95% CI) in which changes in trends in suicide rates occurred we used Joinpoint software version 2.7 (available from http://srab.cancer.gov/joinpoint). Join-point regression is a form of analysis in which trend data are described by a number of contiguous linear segments and join points where trends change (Kim et al, 2000). Permutation tests are used to determine the minimum number of join points required to provide an adequate fit to the data.
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![]() View larger version (26K): [in a new window] [as a PowerPoint slide] |
Fig. 1 Number of suicides v. SSRI and other antidepressant sales in (a) Norway
(19612002), (b) Sweden (19612002), (c) Denmark (19612000)
and (d) Finland (19612003). SSRI, selective serotonin reuptake
inhibitor; DDD, defined daily dose.
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![]() View larger version (25K): [in a new window] [as a PowerPoint slide] |
Fig. 2 Number of suicides (per 100 000 inhabitants, smoothed by 3-year moving
averages) v. SSRI sales by age group in Norway for (a) males and (b)
females, and in Sweden for (c) males and (d) females, for the period
19612002. SSRI, selective serotonin reuptake inhibitor; DDD, defined
daily dose. 45 years
(3-year moving average);, 2544 years (3-year moving average);......,
1524 years (3-year moving average).
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Sweden
In Sweden, in contrast to Norway, suicide rates have been declining
steadily since the 1970s, many years before the rise in SSRI sales in the
early 1990s (Fig. 1b), but the
decline (again in contrast to Norway) also continued after the introduction of
SSRIs in Sweden. It is noteworthy that although age-specific decreases in
suicide rates continued in men and women aged over 25 years throughout the
period of increased SSRI sales, any such declines were less marked or absent
in individuals aged 1524 (Fig. 2c
and d). As in Norway, there was a reduction in the sales of other
antidepressants in the years after the introduction of SSRIs in Sweden
(Fig. 1b).
Denmark
The Danish statistics (Fig.
1c) clearly show a steady rise in male and female suicide rates
throughout the 1960s and 1970s, with a marked peak around 1980. Subsequently,
suicide rates declined in both genders, around 10 years before the
introduction of SSRIs in Denmark and the associated increase in levels of
antidepressant use. The decline in suicide rates has continued over the period
of increased SSRI sales. However, the rates of decline appeared to increase
somewhat in the 1990s, particularly in women.
Finland
In Finland, after increases in suicide rates in the 1960s, 1970s and 1980s,
declines in the overall and male suicide rates, and to a lesser extent in the
female suicide rates, coincided with the introduction and increased sale of
SSRIs (Fig. 1d).
Join-point analysis
For Norway, Sweden and Denmark the most appropriate model of secular trends
in suicide rates included two join points whereas for Finland three join
points provided the best fit to the data. The estimated join points and their
95% confidence intervals are shown in Table
1 for models with one, two and three join points, and the model of
best fit is denoted in bold type. P-values for a test of the
difference in slopes at each join point in the fitted model are also
shown.
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View this table: [in a new window] | Table 1 Results of join-point analysis of suicide rates in the Nordic countries from 1961 to 200020021 |
For the best-fitting model for Norway, the 2 years in which changes in trends occurred were 1967 (95% CI 19631991), when suicide rates began to rise, and 1988 (95% CI 19851999), when suicide rates began to fall. A third change, namely the levelling out of rates described above, was also identified in 1995 (95% CI 19862001) in a model with three join points, although this is not the model of best fit. Similarly, for Sweden 2 years were identified, namely 1968 (95% CI 19651970), when rates began to decline and 1988 (95% CI 19851991), when there was an accelerated rate of decline as described previously by Carlsten et al (2001). The two join points that were identified in the Danish suicide data were 1982 (95% CI 19781986) and 1989 (95% CI 19851995), the latter year corresponding to an increase in the rate of decline that began around 1982. In Finland, the best-fitting model included the following three join points: 1977 (95% CI 19721981), after which suicide rates rose; 1983 (95% CI 19791987), when rates rose again, and 1990 (95% CI 19881993), when they began to fall. In each of the final (best-fitting) models, P-values provide strong evidence (P<0.005) for a difference in slopes at the most recent join point (19881990).
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Statistical analysis suggests that in all four countries a decline (or an acceleration of a pre-existing decline) in suicide rates began around 19881990. This period pre-dates the introduction of SSRIs (and certainly their widespread use), although the 95% confidence intervals for the year in which suicide rates began to decline extend to 1999 for Norway, to 1991 for Sweden, to 1995 for Denmark and to 1993 for Finland. These results are derived from models that fit linear segments to nonlinear data. Although the positions of the join points of these segments provide useful estimates of the years in which trends in suicide rates changed significantly, they represent a simplification of the observed temporal trends, and should therefore be treated with caution.
Our findings contrast with a previous assessment of trends in antidepressant prescribing and suicide rates in the Nordic countries (Isacsson, 2000). The limited period covered by the suicide data that were presented in Isacssons study meant that it was impossible to distinguish between short-term and longer-term trends in suicide rate (Isacsson, 2000). Our analysis suggests that the favourable trends in two of the four countries studied reflect a longer-term favourable trend in suicide rates. However, we did find evidence that declining rates of suicide in Sweden accelerated around 1988, shortly before the widespread use of SSRIs in the 1990s. This finding is consistent with another assessment of the association between antidepressant prescribing and suicide rates in Sweden up to 1997 which reported that the introduction of SSRIs coincided with an increased rate of decline in suicide rates (Carlsten et al, 2001), but that this change pre-dated the large increases in antidepressant sales.
Prescribing trends and suicide rates in other countries
Evidence from other ecological investigations is mixed. Studies in the USA
(Olfson et al, 2003;
Grunebaum et al,
2004), Australia (Hall et
al, 2003) and Hungary
(Rihmer et al, 2001)
report trends which suggest a favourable effect of antidepressants on suicide
rates, whereas findings from Iceland
(Helgason et al,
2004), Italy (Barbui et
al, 1999) and England
(Gunnell & Ashby, 2004) do
not support this. The main limitation of those analyses, as well as those in
the present study, is that there are many complex influences on national
suicide rates, including the availability of lethal methods of suicide,
changing social and economic conditions, changing levels of substance misuse
and birth cohort effects (Gunnell et
al, 2003). Distinguishing between the discrete effects of
changing levels of antidepressant prescribing and those of these other
influences on patterns of suicide is challenging, as many of the factors are
strongly correlated with each other.
Person-based analyses of the association between antidepressants and suicidal behaviour
Recent meta-analyses of placebo-controlled randomised trials of SSRIs
(Whittington (et al,
2004; Fergusson et al,
2005; Gunnell et al,
2005) have provided evidence that SSRIs are associated with an
increased risk of non-fatal suicidal behaviour in children and adults. As most
of these trials were of short duration, it is uncertain whether such increased
risks may be offset by a longer-term reduction in risk among those taking
antidepressants for the recommended period of up to 6 months. There were
insufficient numbers of participants recruited to the trials to allow
investigation of any beneficial or adverse effects of SSRIs on suicide deaths
(Gunnell et al,
2005), highlighting the importance of using observational studies
to investigate this issue. It is noteworthy that observational studies provide
no strong evidence that SSRIs differ from tricyclic antidepressants with
regard to the risk of suicidal behaviour
(Martinez et al,
2005).
Limitations
Our analysis has several limitations. First, we employed an ecological
study design using national sources of prescribing and suicide data. We have
not investigated the influence of antidepressant treatment on suicide risk.
Furthermore, because the prescribing data are sales data rather than data on
person-based consumption of antidepressants, the number of individuals who
took antidepressants will be overestimated. Second, we were unable to
determine the extent to which increases in sales were a result of growing
numbers of each of the following: people who had been newly prescribed an
SSRI; long-term users; or a combination of the two. Third, we have not taken
into account other influences on temporal trends in suicide rates (e.g.
changes in the levels of unemployment, divorce or substance misuse)
(Gunnell et al,
2003). Fourth, we were unable to obtain age- and gender-specific
prescribing data for the four countries, so we were unable to investigate
whether age-specific trends in suicide rates mirrored those for prescribing.
However, analyses from other countries suggest that antidepressant prescribing
increased by 2-fold or more in all age/gender categories in the 1990s
(Middleton et al,
2001; Hall et al,
2003), which indicates that our use of all-age data will not
seriously bias our interpretation of the overall trends within specific
age/gender categories. Finally, our analysis was restricted to four countries.
As highlighted above, there is mixed evidence from other countries concerning
the effect of increased levels of antidepressant prescribing on suicide
rates.
Implications
Although there is broad consensus about the effectiveness of SSRIs in
treating depression, the evidence that the decline in suicide rates which was
seen in Norway, Sweden, Denmark and Finland in the 1990s resulted from
increased antidepressant prescribing is not clear-cut. A more detailed
understanding of the factors that have contributed to recent declines in
suicide rates in the Nordic countries is required. Elucidation of these
factors will help to inform the development of evidence-based suicide
prevention policies.
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LIMITATIONS
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