Effects begin about thirty minutes after ingestion, peak in two hours, and fade after nine to twelve hours. LSD induces numbness, fatigue, rapid reflexes, tremors, pupil dilation, increased heart rate, increased blood pressure, reduced appetite, chills and nausea. Tests to determine brain and chromosomal damage have been inconclusive. Pregnant women should not use LSD because of possible harm to their fetuses. Short-term memory is often temporarily impaired.
Hallucinations are more common at higher doses.
Some users may experience a cluster of frightening effects, such as paranoia, panic and delusions of persecution. LSD might also unmask pre-existing emotional problems that are normally hidden. A small number of users suffer psychotic episodes which last for weeks. Certain parts of an original drug experience may recur without subsequent drug ingestion. Such flashbacks are usually brief, but can last hours.