from what i know, the main issue is sativa is more THC heavy and indica has more CBD, so they do tend to have that effect on people, but it also is different person to person sometimes.
The other thing to remember is that pretty much all weed is a hybrid of some kind. Theres no 100% sativa or indica, its a mix of both. The strain or terpene profile is usually more important than THC percentage.
from what i know, the main issue is sativa is more THC heavy and indica has more CBD, so they do tend to have that effect on people, but it also is different person to person sometimes.
The other thing to remember is that pretty much all weed is a hybrid of some kind. Theres no 100% sativa or indica, its a mix of both. The strain or terpene profile is usually more important than THC percentage.