Do Blind / Normal games affect MMR?

I swear, I've been on a bit of a losing streak lately (haven't really been playing too seriously and been picking more fun picks in norms because I want to branch out [e.g. tank karma, full AD poppy etc.]).

But every successive game it seems like i'm going up against worse and worse teammates and opponents. Some of the mistakes and decisions thes players make are just downright awful. Towerdiving at 20% health against a CC heavy bot lane, failing to notice anything on the minimap, ignoring objectives to farm, and giving up on the game prematurely. This isn't just my team; the enemy team also makes horrible calls as well.

Now I'm on the low side of Bronze here (mid Bronze, actually, but same thing) but I've noticed a pretty steep decline, and was wondering if my losses actually affect MMR and therefore who I am matched with.

(This is not an "I deserve XXX" because right now I'm very sure I'm a Bronze 3 skill level [I'm really not that good]; it just feels like I'm playing a bronze 5 or even bronze 6 game sometimes...)

Note that when I play with my friends / duo partners who are in Silver and Gold there is no issue, my main reason to think MMR affects this.