Rohypnol causes partial amnesia; individuals are unable to remember certain events that they experience while under the influence of the drug. This effect is particularly dangerous when Rohypnol is used to aid in the commission of sexual assault; victims may not be able to clearly recall the assault, the assailant, or the events surrounding the assault.
Rohypnol use in the US, according to the 2010 Monitoring the Future Survey, has increased by 0.2 percent since 2009. However, use has been relatively stable from 1999 to 2010, with yearly use estimates ranging from 0.6 to 0.9 percent of 8th to 12th grade respondents.
It is difficult to estimate the number of Rohypnol-facilitated rapes in the United States. Very often, biological samples are taken from the victim at a time when the effects of the drug have already passed and only residual amounts remain in the body fluids. These residual amounts are difficult, if not impossible, to detect using standard screening assays available in the United States.