Why do people get nightmares?

Nightmares. Nightmares frequently happen in post-traumatic stress disorder, but also in 20-40% of kids between age 5-12 without any psychopathology. Creative people with "thin boundaries" on psychological tests may have them. Medications like antidepressants, certain antihypertensives, antiparkinsonian drugs, & barbiturates can cause nightmares; also withdrawal from alcohol, barbiturates, and benzodiazepines.