To clear up the dissonance, I interpret that "Side effect" does not mean "Unintended consequence" in this case, it means "Not the root cause of brain changes".

To clear up the dissonance, I interpret that "Side effect" does not mean "Unintended consequence" in this case, it means "Not the root cause of brain changes". Sure, I intended to trip, but the trip was caused by something deeper. As in: "The nice fuzzy warm feeling of sitting around a fire is a side effect of self-sustaining exothermic oxidization of organic volatiles in dried wood" Of course I made a fire for the warmth on my face / clothes. It's just the warmth I feel is a side effect of a deeper process where the heat sustains the reaction. It just so happens I'm around to harvest some of the waste heat.