Among those using illicit drugs for the first time in 2007, the most popular substances were marijuana and prescription painkillers—each used by roughly the same number of Americans aged 12 and older. Non-medical use of painkillers rose 12%.

One in ten high school seniors in the US admits to abusing prescription painkillers.

Misuse of painkillers represents three-fourths of the overall problem of prescription drug abuse. The painkiller hydrocodone is the most commonly diverted and abused controlled pharmaceutical in the US.

Methadone, once used in addiction treatment centers and now used by doctors as a painkiller, was found as the cause of 785 deaths in one state alone, Florida, in 2007.

Prescription drug abuse is also climbing in older Americans, particularly involving anti-anxiety drugs such as Xanax and painkillers such as OxyContin.

In the UK, tens of thousands of people are said to be dependent on painkillers such as Solpadeine and Neurofen Plus.

Doctors and rehabilitation therapists report that prescription painkiller abuse is one of the most difficult addictions to treat.