It can cause psychological and physical dependency on the drug which can lead to dilated pupils, increased pulse rate, elevated blood pressure, insomnia, loss of appetite, paranoia, and seizures. It can also cause death by disrupting the brain's control of the heart and respiration. Other stimulant and amphetamine use can have the same effect as cocaine and cause increase heart rates and blood pressure that can result in a stroke or heart failure. It can also lead to psychosis, hallucinations, paranoia and even a physical collapse. Depressants and barbiturates can cause physical and psychological dependence that can lead to respiratory depression, coma, and death, especially when used in concert with alcohol.
Withdrawal can lead to restlessness, insomnia, convulsions and even death.
LSD, PCP, mescaline and peyote are classified as hallucinogens. Hallucinogens interrupt the brain's messages that control the intellect and keep instincts in check. Large doses can produce convulsions and coma, heart and lung failure. Chronic users complain of persistent memory problems and speech difficulties for up to a year after their use. Because the drug stops the brain's pain sensors, drug experience may result in severe self-inflicted injuries.