Barr’s paper [1] was impressive to show the clear relationship between the increase of suicides in England and the financial crisis between 2008 and 2010. This trend was also seen between 1988 and 1997 in Japan, however, it could not be found between 2004 and 2007 [2]. Interestingly, the average sleep duration of people in Japan of age 10 years or more was 459 minutes in 1990, 452 in 1995, 443 in 2000, 442 in 2005, and 434 in 2010, respectively [2]. According to OECD, the average sleep duration in 2009 is reported to be 503 minutes in UK, and 470 minutes in Japan [3]. Recently, a hypothesis that more sleep will bring less suicide in Japan has been proposed [4]. This hypothesis has been based on recent reports on suicide, serotonin and sleep [2, 4]. According to this hypothesis, financial crisis might play a significant role on the occurrence of suicide when sleep duration was preserved, while it would fail to affect suicide occurrence when sleep duration decreases below a certain level that might be determined by biological necessities.

References
1. Barr B, Taylor-Robinson D, Scott-Samuel A, McKee M, Stuckler D. Suicides associated with the 2008-10 economic recession in England: time trend analysis. BMJ 2012;345:e5142
2. Kohyama J. Sleep, serotonin and suicide in Japan. J Physiol Anthropol. 2011; 30:1-8.
3. Society at a Glance 2009 OECD Social Indicators (2009) Special focus: measuring leisure in OECD countries. http://www.sourceoecd.org/pdf/societyataglance2009/81200
9011e-02.pdf (accessed on Aug. 21, 2012)
4. Kohyama J. More sleep will bring more serotonin and less suicide in Japan. Med Hypotheses. 2010;75:340.

Competing interests: None declared