Among 16,255 Swedish adolescents, 541 reported past psychedelic use, and 99% of those also used other drugs. After adjusting for other drug use, psychedelic use was associated with fewer psychotic symptoms. However, the link between psychedelic use and manic symptoms depended on genetic vulnerability: adolescents with higher genetic risk for schizophrenia or bipolar I disorder showed more manic symptoms after psychedelic use. The authors urge caution due to study limitations.
In a large twin study using the Swedish Twin Registry, people who reported using psychedelics had lower odds of having a history of migraine. Among identical twins, the twin who used psychedelics was less likely to have migraine than their co-twin who did not. The association was significant in males but not in females. These results suggest a possible link between psychedelic use and reduced migraine likelihood, with sex differences that need further study.