The AFL temporarily withdrew three players with illicit drug problems from competition, and has "retired" another three who were unable to control their addictions.
The league has also used "intelligence" gleaned while working with players under the voluntary illicit drugs policy to identify those with possible criminal connections and the potential to use performance enhancing drugs.
The AFL's chief medical officer Peter Harcourt told an anti-doping conference in Zurich last November that while the majority of players who transgressed did so because of "one-off, stupid, risk taking behaviour that happens in social situations," about 5 per cent of those who tested positive had mental problems. That number rose to 50 per cent for players who found themselves on two strikes.
He said another group was "basically disengaged, probably a bit narcissistic, a bit anti-social, and we think this is where we're starting to push our knowledge about these individuals - who have clearly got some regular criminal contacts - into our targeting program and our test distribution under our anti-doping code to look for performance enhancing drugs, because we're now learning that all these different types of criminal activity are all linked."
While Harcourt said most players had been able to modify their behaviour after returning a positive test, he revealed the league had "had to retire" three players since the poliicy was formed with the support of the players 10 years ago. Another, former Hawthorn midfielder Travis Tuck, is the only player to have reached three strikes, been named publicly and suspended.
Harcourt told the conference that three players had had psychotic reactions to illicit substances, five had taken illicit substances to deal with certain psychiatric symptoms and the league had needed to "temporarily withdraw" another three players "because of substance abuse issues that needed to be treated."
A further five had exhibited "attitudinal and personality type issues, but the bulk are just silly, risk taking behaviour," he said.
"If you think about it, you've got an open situation where you're talking openly with a player about their substance abuse. Part of that analysis is to work out the attitude of the individual and how they're engaged in what you're dealing with."
The players agreed to take part in out-of-competition testing for illicit substance use in 2005, provided there was confidentiality and that they were supported with counselling and medical assistance, which Harcourt enphasised in his address.
In 2013, 15 players tested positive to illicit substances - down from 26 in 2012 - and Harcout told the conference that drug use by footballers was significantly lower than it was for Australian men in the same age bracket. The league conducted 1998 tests in 2013, up from 1979 in 2012. One player reached his second strike, down from two in 2012.
The AFL Players Association said while it was unfortunate Harcourt's comments had been made public via YouTube, they illustrated the role the illicit drug policy played in supporting player health and wellbeing.
“We understand that Dr Harcourt made these comments at a medical conference and was not aware it was being filmed," said Ian Prendergast, the AFLPA's general manager of player relations, in a statement.
"The IDP is an educational and medical based model, which exists on the basis of confidentiality for all individuals involved.
"We know that the medical approach to drug use is the best way to protect players’ health and wellbeing. It is imperative that privacy and confidentiality of players is maintained, and that the comments made by Dr Harcourt are not sensationalised."