Can pure ocd cause a lot of mood changes?

Not directly: Obviously, having severe OCD symptoms can be discouraging or even depressing, but mood changes are not an inherent part of ocd. When depression sometimes coincides with OCD — and it does somewhat more than chance would suggest — it is diagnosed separately. On a related note, ssri antidepressants also can treat OCD symptoms, as they help anxiety disorders too.

Very Possible: Ocd has very high mood impact. One can have a concurrent mood disorder which can effect your OCD or be secondary in my experience most people who have significant OCD have mood issues.

Unlikely: Unless it is comorbid with bipolar affective d/o.

Ocd: It causes anxiety, and if it goes untreated and becomes chronic , it can affect moods.