adrenochrome

Several small-scale studies (involving 15 or fewer test subjects) conducted in the 1950s and 1960s reported that adrenochrome triggered psychotic reactions such as thought disorder and derealization

Interesting. This is probably what makes people, who would normally not kill or do other horrible acts, to do so in conditions of extreme distress and then later have a feeling of it never have actually happened, making them still be able to live life with about the same personality as before.