Do long CSS selectors make page rendering slow?

I've heard that having really long selectors in your CSS makes your page rendering slow.

Since I'm used to using SASS, so I always end up having really long selectors. Something like this:

.parent .child .element .child .child2 .child3 .child4 .child5{
    ...
}

Is it true that long selectors make rendering slow? and are there any ways to avoid this from happening?