"Over half (57 per cent) of all deaths related to drug poisoning involved an opiate drug. In 2011, as in previous years, the most commonly mentioned opiates were heroin and/or morphine, which were involved in 596 deaths (see Background note 8). For males, heroin/morphine was involved in more deaths than any other substance.
"However, the mortality rate for males has fallen sharply in the last two years, down from 27.9 deaths per million population in 2009 to 17.1 in 2011. This is a 39 per cent fall and is the lowest rate since 1997. The corresponding rate in females was much lower at 4.5 deaths per million population in 2011, and has not changed significantly since 1997, when the rate was 2.2 deaths per million population."
"Statistical Bulletin: Deaths Related to Drug Poisoning in England and Wales, 2011" (London, England: Office for National Statistics, Aug 29, 2012), pp. 16-17.