Physical side effects of crack include body burn-out and malnutrition and possible liver damage. The drug depletes levels of dopamine, a neurotransmitter involved in regulation of mood, attention, and motivation.

As was the case from 2002 through 2007, the rate of substance dependence or abuse for males aged 12 or older in 2008 was about twice as high as the rate for females. For males in 2008, the rate was 11.5 percent, which was down from the 12.5 percent in 2007, while for females, it was 6.4 percent, which was higher than the 5.7 percent in 2007. Among youths aged 12 to 17, however, the rate of substance dependence or abuse among males was lower than the rate among females in 2008 (7.0 vs. 8.2 percent).

Use of illicit drugs and alcohol was more common among current cigarette smokers than among nonsmokers in 2009, as in prior years since 2002. Among persons aged 12 or older, 22.4 percent of past month cigarette smokers reported current use of an illicit drug compared with 4.5 percent of persons who were not current cigarette smokers. Past month alcohol use was reported by 67.1 percent of current cigarette smokers compared with 47.2 percent of those who did not use cigarettes in the past month. The association also was found with binge drinking (44.8 percent of current cigarette smokers vs. 17.2 percent of current nonsmokers) and heavy drinking (16.4 vs. 3.9 percent, respectively).

Among persons aged 12 or older in 2007-2008 who used pain relievers nonmedically in the past 12 months, 55.9 percent got the drug they most recently used from a friend or relative for free. Another 18.0 percent reported they got the drug from one doctor. Only 4.3 percent got pain relievers from a drug dealer or other stranger, and 0.4 percent bought them on the Internet. Among those who reported getting the pain reliever from a friend or relative for free, 81.7 percent reported in a follow-up question that the friend or relative had obtained the drugs from just one doctor.