A new study analyzed data from the Swedish Twin Registry, a national dataset that includes self-reported drug use and psychotic and manic symptom occurrence.

The researchers’ analyses found no significant association between psychedelic use and psychotic symptoms, but in comparing identical twin pairs in which one had taken psychedelics while the other had not, the twin who’d tried psychedelics was more likely to report experiencing manic symptoms.

In the twin data researchers reviewed, mania was also strongly correlated with a genetic predisposition to schizophrenia and to bipolar I disorder.

In other words, those who experienced manic symptoms after psychedelic use may have been more genetically prone to mental illnesses.