High Performance Sport New Zealand says there's a danger the New Zealand Rugby Union won't get an accurate assessment of prescription drug abuse from a survey of players.
The NZRU admitted on Thursday that All Blacks Cory Jane and Israel Dagg mixed sleeping pills with alcohol on a night out, three days before the All Blacks' 2011 World Cup quarter-final against Argentina.
With rugby league having similar problems the NZRU says they will survey players to see how widespread the problems is.
But the chief executive of HPSNZ Alex Baumann admits with a formal survey there's a possibility players may not respond accurately, even if it's anonymous.
Baumann says he hopes players are upfront but any approach needs to be multi-faceted with discussions with players and also advice from medical staff, nutritionists and psychologists