Crack is far more addictive than heroin or barbiturates. Repeated use of crack can lead to addiction within a few days. Once addicted, many users have turned to stealing, prostitution, and drug dealing in order to support their habit. The effects of crack are felt within 10 seconds. The physical effects include dilated pupils, increased pulse rate, elevated blood pressure, insomnia, loss of appetite, tactile hallucinations, paranoia, and seizures.
Continued use can produce violent behavior and psychotic states similar to schizophrenia.
Cocaine in any form, but particularly in the purified form known as crack, can cause sudden death from cardiac arrest or respiratory failure. Marijuana use causes a substantial increase in the heart rate, bloodshot eyes, a dry mouth and throat, increased appetite, and it may impair short-term memory and comprehension, alter sense of time, and reduce ability to perform tasks requiring concentration and coordination, such as driving a car. Research also shows that motivation and cognition may be altered, making the acquisition of new information difficult. Because users often inhale the unfiltered smoke deeply and then hold it in their lungs as long as possible, marijuana is damaging to the lungs and pulmonary system. Marijuana smoke contains more cancer-causing agents than tobacco smoke.