LSD effect on brain.

LSD is an hallucinogen

Hallucinogens powerfully affect the brain, distorting the way our five senses work and changing our impressions of time and space. People who use these drugs a lot may have a hard time concentrating, communicating, or telling the difference between reality and illusion.

How Hallucinogens Affect Your Senses

Your brain controls all of your perceptions -- the way you see, hear, smell, taste, and feel. How does your brain communicate with the rest of your body? Chemical messengers transmit information from nerve cell to nerve cell in the body and the brain. Messages are constantly being sent back and forth with amazing speed.

Your nerve cells are called neurons, and their chemical messengers are called neurotransmitters. When neurotransmitters attach to special places on nerve cells (called receptors), they cause changes in the nerve cells.

This communication system can be disrupted by chemicals like hallucinogens, and the results are changes in the way you sense the world around you.

LSD: The Most Commonly Used Hallucinogen

LSD causes its effects mainly by activating one type of receptor for serotonin. Because serotonin has a role in many important functions, LSD use can have many effects. These may include sleeplessness, trembling, and raised heart rate, and blood pressure. LSD users may feel several emotions at once (including extreme terror), and their senses may seem to get crossed -- giving the feeling of hearing colors and seeing sounds.

Even a tiny speck of LSD can trigger these effects. And LSD has an unusual "echo." Many users have flashbacks -- sudden repetitions of their LSD experiences -- days or months after they stop using the drug.