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• Re:Conceptual fallacy
  Annette Erlangsen
  Published on: 18 November 2009
• Conceptual fallacy
  Göran Isacsson
  Published on: 27 October 2009

• Published on: 18 November 2009

  Re:Conceptual fallacy

  • Annette Erlangsen, Senior Researcher
  • Other Contributors:
    • V Canudas-Romo, and Y Conwell

  Assumptions beyond the current level of evidence

  We hereby acknowledge the e-letter by Prof. Goran Isacsson (dated 27th October, 2009) to our study on antidepressants and the change of the suicide rate in older adults [1,2]. We indeed appreciate the comment, even as our opinions differ.

  Prof. Isacsson postulates that antidepressants (primarily SSRIs) are accountable - not only for the reduction in sui...

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  Assumptions beyond the current level of evidence

  We hereby acknowledge the e-letter by Prof. Goran Isacsson (dated 27th October, 2009) to our study on antidepressants and the change of the suicide rate in older adults [1,2]. We indeed appreciate the comment, even as our opinions differ.

  Prof. Isacsson postulates that antidepressants (primarily SSRIs) are accountable - not only for the reduction in suicides occurring among those currently treated with the drug - but also for the rate reduction in the population not receiving treatment. This implies assuming that doctors have improved their rate of identifying and treating depression to such an extent that proportionally more suicidal persons are commencing a treatment (and/or fewer are dropping out of treatment).

  It is true that the number of persons beginning a treatment with SSRIs has increased over time. However, we know that SSRIs are prescribed for a wider range of symptoms apart from mood disorders, such as: pain syndromes, anxiety, irritable bowel syndrome, and sexual dysfunction [3- 6]. Over the studied period proportionally more SSRI were prescribed [2]. This could indicate that the specificity with which antidepressants were prescribed for depressive symptoms might have decreased over time.

  Evidence-based studies show that suicide, also among older adults, is an outcome of a many factors, of which many are likely to vary over time [7,8]. Opposed to the current years of economic recession[9], the financial prosperity of the examined period might be accountable for some of the decline in the suicide rate. The decline in the suicide rate both among those who are in treatment with antidepressants as well as those who are not in treatment is, thus, likely to be influenced by many other factors.

  Opposed to ecological studies, it should be mentioned that our study used individual-level data where it is possible to establish a direct link between antidepressant users and persons dying by suicide.

  Based on the current state of evidence, we feel that it is untenable to conclude that SSRI is the only contributing factor to the decline in the overall suicide rate.

  References

  1 Isacsson G. Conceptual fallacy [electronic letter]. http://jech.bmj.com/content/62/5/448/reply#jech_el_2395

  2 Erlangsen A, Canudas-Romo V, Conwell Y. Increased use of antidepressants and decreasing suicide rates: A population-based study using Danish register data. J Epidemiol Community Health 2008;62:448-54.

  3 Sindrup SH, Bjerre U, Dejgaard A. The selective serotonin reuptake inhibitor citalopram relieves the symptoms of diabetic neuropathy. Clin Pharmacol Ther 1992;52:547-52.

  4 Creed F. How do SSRIs help patients with irritable bowel syndrome? Gut 2006;55:1065-7.

  5 Giuliano F. 5-Hydroxytryptamine in premature ejaculation: opportunities for therapeutic intervention. Gut 2007;30:79-84.

  6 Rahme E, Dasgupta K, Turecki G, et al. Risks of Suicide and Poisoning Among Elderly Patients Prescribed Selective Serotonin Reuptake Inhibitors: A Retrospective Cohort Study. J Clin Psychiatry 2008;69:349- 57.

  7 Hawton K, van HK. Suicide. Lancet 2009;373:1372-81.

  8 Conwell Y, Thompson C. Suicidal behavior in elders. Psychiatr Clin North Am 2008;31:333-56.

  9 Gunnell D, Platt S, Hawton K. The economic crisis and suicide. BMJ 2009;338:b1891.

  Conflict of Interest:

  None declared

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  Conflict of Interest:
  None declared.

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• Published on: 27 October 2009

  Conceptual fallacy

  • Göran Isacsson, Professor

  Erlangsen et al. linked data from an individual-based prescription database in Denmark with data from the cause-of-death register for the two years 1996 and 2000[1]. They found 88 fewer suicides in 2000 than in 1996, 7 fewer among the population that was treated with antidepressants and 81 fewer among the untreated population. Based on “decomposition” analysis of these data, the authors concluded, “Individuals in active tre...

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  Erlangsen et al. linked data from an individual-based prescription database in Denmark with data from the cause-of-death register for the two years 1996 and 2000[1]. They found 88 fewer suicides in 2000 than in 1996, 7 fewer among the population that was treated with antidepressants and 81 fewer among the untreated population. Based on “decomposition” analysis of these data, the authors concluded, “Individuals in active treatment with antidepressants seem to account for 10 % of the decrease in the suicide rate” and “the major share (…) seems to be explained through other components.” This conclusion would contradict the large number of ecological studies and some individual-based studies that suggest the opposite, that antidepressant usage was the main cause of the decrease in suicide[2-4]. I believe there is a major conceptual fallacy in the Erlangsen et al. basic assumption, however. The authors obviously assumed that they should expect the main decrease in suicide in the population treated with antidepressants if antidepressant medication was the main cause of the decrease in suicide. When their “decomposition” instead indicated that 90 % of the decrease had occurred in the population not treated with antidepressants, they concluded that antidepressant medication was not the main cause. I believe the correct conclusion, however, is the opposite, since the basic assumption was wrong. The increased treatment in the general population (+27,835) will increase the probability of suicides as well as non-suicides to be “treated”. Thus, the actual decrease of 81 “untreated suicides” may be a consequence of just the increased treatment; they were no more untreated. If these individuals still commit suicide when treated, the number of “treated suicides” will increase as much as the number of “untreated suicides” has decreased (i.e. +81 cases). If antidepressants prevent suicide, however, the number of “treated suicides” will INCREASE LESS (e.g. only 40 cases more if one assumes 50 % effectiveness). That is the correct basic assumption that Erlangsen et al. should have made. Thus, the observed result of 81 less “untreated suicides” and 7 less “treated suicides” suggests that antidepressants indeed have been the main cause of the decrease in suicide. The fact that “treated suicides” did not increase by about 40 cases as might be expected may be interpreted as fewer therapeutic failures resulting from improved quality of treatment with antidepressants.

  1 Erlangsen A, Canudas-Romo V, Conwell Y. Increased use of antidepressants and decreasing suicide rates: a population-based study using Danish register data. J Epidemiol Community Health 2008;62:448-54. 2 Isacsson G, Rich CL. Antidepressant drug use and suicide prevention. Int Rev Psychiatry 2005;17:153-62. 3 Isacsson G, Holmgren A, Ösby U, et al. Decrease in suicide among the individuals treated with antidepressants. A controlled study of antidepressants in suicide, Sweden 1995-2005. Acta Psychiatr Scand 2009;120:37-44. 4 Ludwig J, Marcotte DE, Norberg K. Anti-depressants and suicide. J Health Econ 2009;28:659-76.

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  Conflict of Interest:
  None declared.

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