From the article:

Compared with experiences with forms of LSD purchased illegally on the street, the study’s grade of MM120 did not appear to induce “bad trips,” Karlin said.

“LSD is difficult to manufacture with high purity and tends to degrade quickly in the presence of light and water,” Karlin said. “We’re manufacturing it to pharmaceutical industry standards, a highly pure version that is also shelf stable. So that’s a critical difference.”

Most adverse effects in the study were rated as mild to moderate by participants, occurring mostly on the day of the study, Karlin said. Those included euphoric feelings, illusions and hallucinations, anxiety, abnormal thinking, headaches, dizziness, nausea, excessive sweating, vomiting, numbness or tingling of the skin, and pupil dilation.

I do worry a bit whenever these articles come out that people will just read the headline, go out and procure some hallucinogenics for themselves, and then not have a good time because they didn't read the fine print.

And that’s why we need to legalize it all - so we can study it and have non-anecdotal evidence.