All forms of cannabis have negative physical and mental effects. Several regularly observed physical effects of cannabis are a substantial decrease in the heart rate, bloodshot eyes, dry mouth and throat, and increased appetite.

Use of cannabis may impair or reduce 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 students do not retain knowledge when they are "high". Motivation and cognition may be altered, making the acquisition of new information difficult. Marijuana can also produce paranoia and psychosis.

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.

Long-term users of cannabis may develop psychological dependency and require more of the drug to get the same effect. The drug can become the center of their lives.

Cocaine stimulates the central nervous system. Its immediate effects include dilated pupils and elevated blood pressure, heart rate, respiratory rate, and body temperature. Occasional use can cause a stuffy or runny nose, while chronic use can ulcerate the mucous membrane of the nose. Injecting cocaine with unsterile equipment can cause AIDS, hepatitis, and other diseases. Preparation of freebase, which involves the use of volatile solvents, can result in death or injury from fire or explosion. Cocaine can produce psychological and physical dependency, a feeling that the user cannot function without the drug. In addition, tolerance develops rapidly.

Crack or freebase rock is extremely addictive, and its effects are felt within ten (10) seconds. The physical effects include dilated pupils, increased pulse rate, elevated blood pressure, insomnia, loss of appetite, tactile hallucinations, paranoia, and seizure.

The use of cocaine can cause death by disrupting the brain's control of the heart and respiration.

Stimulants can cause increased heart and respiratory rates, elevated blood pressure, dilated pupils and decreased appetite. In addition, users may experience sweating, headache, blurred vision, dizziness, sleeplessness, and anxiety. Extremely high doses can cause a rapid or irregular heartbeat, tremors, loss of coordination, and even physical collapse. An amphetamine injection creates a sudden increase in blood pressure that can result in stroke, very high fever, or heart failure.

In addition to the physical effects, users report feeling restless, anxious, and moody. Higher doses intensify the effects. Persons who use large amounts of amphetamines over a long period of time can develop an amphetamine psychosis that includes hallucinations, delusions, and paranoia. These symptoms usually disappear when drug use ceases.