Side effects, by definition, are unintended effects. Whether “bad” or “good” is irrelevant and subjective in most cases. LSD was synthesized by Hoffman in hopes of making a mild stimulant, and to increase respiration rates in patients. Now, LSD does all that very well, but there is a side effect…
In some cases with pharmaceutical development, side-effects are the cause for “off-label” prescriptions, such as certain antidepressants for quitting smoking.
I like to think of the entire gamut as “effects”. Side-ness of the effect is relative to the intended outcome.
When i studied psychopharmacology, most of the time was spent learning how to balance the effects, not what-does-what. Cannabis has been primarily studied for the effects of THC, CBD, CBN… There is a lot more to the plant than that.