Use can also lead to psychosis, hallucinations, paranoia, and even 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 messages that control the intellect and keep instincts in check.
Large doses can produce convulsions and coma, heart and lung failure.
Users complain of persistent memory problems, speech difficulties, and flashbacks . Because these drugs stop the brain's pain sensors, drug experiences may result in severe self-inflicted injuries. Users of narcotics, such as heroin, codeine, morphine and opium develop dependence and increase the likelihood of an overdose that can lead to convulsions, coma and death. This is a very high risk activity. Permanent brain, liver and kidney damage, bronchitis, heart arrhythmias, seizures, coma and death can occur even with initial use.