Hallucinogens are chemical agents that induce alterations in perception, thinking, and feeling. Examples include LSD and PCP. Effects are noted within 20-30 minutes of ingestion and include dilatation of the pupils, blood pressure elevation, abnormally rapid heart rate, involuntary trembling or quivering, overactive reflexes, and the psychedelic phase (consisting of euphoria or mixed mood changes, visual illusions and altered perceptions, a blurring of boundaries between self and non-self, and often a feeling of unity with the cosmos). In addition to persistent or recurrent hallucinations that are regularly produced, adverse effects of hallucinogens are frequent and include bad trips, post-hallucinogen perception disorder or flashbacks, delusional disorder (the individual becomes convinced that the perceptual distortions experienced correspond with reality), and affective or mood disorder, which consist of anxiety, depression, or mania (typically, the individual feels that he or she can never be normal again and expresses concern about brain damage as a result of taking the drug).