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Review date: June 2021

Citation: Catalano et al., 2021. Sildenafil and suicide in Sweden. European Journal of Epidemiology

 

Imagine if the solution to our rising suicide rate was as simple as a pill — the little blue pill. That’s the implication of an article1 titled ‘Sildenafil and suicide in Sweden’, published online on 1 April 2021 in the European Journal of Epidemiology.

In 2002, the suicide rate among Australian males was 16 per 100,000 (perhaps its lowest ever) we then reached 20 per 100,000 (a 25% increase) in 20192. With this recent rise, and the expectation that COVID-19 will see a further increase, 2020 and 2021 is likely to see us hit record highs.

Suicide rates are 3-4 times higher in Australian men than women2, although women are more likely than men to attempt suicide3. This gender paradox likely reflects the lethality of the method chosen, rather than individuals’ intent to die4. Whether men and women differ in the predisposing (e.g. family history), mediating (e.g. substance use) or precipitating (e.g. life events) factors that contribute to individuals’ risk of suicide is unknown4. The Authors of Suicide and sildenafil in Sweden wondered if sexual intimacy, or lack thereof, could be a factor.

Despite the prominence of both suicide and sildenafil in the title of the recent European Journal of Epidemiology publication, these dependent and independent variables of the study are incidental, serving as proxies for mental health and sexual intimacy, respectively. The rationale for the study is the idea, stemming from “intuition, theory and observational data” that sexual intimacy enhances mental health. The authors discuss why testing this hypothesis is difficult, before describing their approach: comparing the number of suicides in 50-59-year-old male Swedes before and after sildenafil became off-patent.

The study’s authors reason that expiration of the patent on sildenafil is a “valid estimator” of the effect of “novel use of sildenafil by men aged 50-59” (i.e. men using sildenafil who did not previously) on suicide count because:

  1. The expiry of the patent on sildenafil precedes novel use of sildenafil by men aged 50-59.
  2. The expiry of the patent only affects suicides only through novel use of sildenafil.
  3. The expiry of the patent and suicide count share no common cause.

The trouble is:

  1. The authors provide no evidence to support the assumption that sildenafil use by men aged 50-59 changed at all. They state only that, “The number of Swedish men using sildenafil averaged 62,000 per year from 2007 to 2012. That number increased to 101,000 for the years 2014–2017." These data are for men of all ages.
  2. The expiry of the patent may have coincided with some other event that affected suicides.
  3. Just because expiry of the patent and suicide count do not share a cause does not mean that an unestablished intermediate event (like increased use of sildenafil by men aged 50-59) links them in a causative way.

The investigators use some complicated analytic methods to estimate the expected number of suicides in the 18-month period after sildenafil went off patent, based on the 102 months prior. It’s not sufficient to just compare the mean number of suicides before and after, they tell us, but they don’t provide any information to support this claim.

The authors state that 4-5 fewer men aged between 50-59 committed suicide each month after sildenafil went off-patent. The reduction in suicides was detectable in November 2013, four months after the patent expired. The authors don’t provide any explanation on why there was a delay.

The authors do offer a rationale for limiting the period of their analysis to the 18 months (up to December 2014) after sildenafil went off-patent: “Projecting beyond 2014 from parameters estimated for 2005–June 2013 strikes us as risky” although, “we did so through 2016…”. The effect became “statistically undetectable… in January 2015”.

The same assumptions that lead to the authors' suggestion that cheaper sildenafil reduced suicides in men aged 50-59 are also used to explain the lack of an effect in men aged 40-49, 60-69, or all men other than those aged 50-59. What is the basis for claiming that these other groups of men “do not use sildenafil”, or “have lower expectations of sexual intimacy involving erection”? The source of Swedish sildenafil statistics cited by the authors5 shows that 60% of Sweden’s sildenafil users are men aged 60 or older!

In 1998, psychologist Norbert Kerr coined the term HARKing (Hypothesizing After the Results are Known) for the dubious practice of presenting, as an a priori hypothesis, one that is made up after data are collected and analysed6. With the perfect fit of the hypothesis and results, arbitrary decisions about methodology and selective use of available evidence to support the design and interpretation of the study, Suicide and sildenafil in Sweden feels ‘ARKed’.

Challenged by the authors’ statement that, “Only replication can determine whether the association we found in Sweden describes other societies…”, we looked at our Australian data.

In the year before sildenafil came off-patent (2012), 1,930 Australian men (17 per 100,000) took their own lives. In 2014, 2,208 (almost 19 per 100,000) Australian men died by suicide.

We don’t need complicated statistical analyses to know that suicide is a major problem when it comes to men’s health (and the health of women). What we do need are research projects deliberately aimed at finding effective ways to identify people at risk of suicide, and how to provide support to those at risk, not spurious correlations.

 

[1] Catalano et al., 2021. Sildenafil and suicide in Sweden. European Journal of Epidemiology

[2] Australian Institute of Health and Welfare, 2021. Suicide and self-harm monitoring. Available from https://www.aihw.gov.au/suicide-self-harm-monitoring 

[3] Turecki & Brent, 2016. Suicide and suicidal behaviour. The Lancet

[4] Denning et al., 2000. Method Choice, Intent, and Gender in Completed Suicide. Suicide and Life-Threatening Behavior

[5] Health Magazine. Use of Viagra across the Nordics: Statistical Analysis https://drseb.com/impotence/viagra/ statistics-nordics/

[6] Kerr, 1998. HARKing: Hypothesizing After the Results are Known. Personality and Social Psychology Review