Hallucinogenic drugs are among the oldest known group of drugs used for their ability to alter human perception and mood. This group includes LSD, Psilocybin, Phencyclidine, Ecstacy and others. These drugs can cause both physical and psychological effects on the persons consuming these drugs. The physical effects of these drugs include: dilated pupils, elevated body temperature, increased heart rate and blood pressure, appetite loss, sleeplessness, tremors, headaches etc. Psychological effects of these drugs includes hallucinations and illusions as well, as the amplification of sense, and the alterations of thinking and self awareness. Long term effects of hallucinogens are very dangerous which includes flashbacks, mood swings, impaired thinking, unexpected outbursts of violence and depression which may lead to death or suicide.
These drugs also show major effects on the functioning of the brain. They change the feelings and emotions of the user and total alteration of senses can occur as a result of using hallucinogens. The users of these drugs may see the sound or can hear the colors. Sensory disturbances such as hallucinations and delusions are also caused by hallucinogens. It may so happen that the user may go through extreme mood swings or experience various different emotions at one time. Hallucinogenic drugs have effect on the post synaptic activity of serotonergic neurons. Effects of these drugs depends on the environment, mood and personality of the user, the quantity and the strength of the drug.