No but. Depression is not generally considered to be a cause of obsessive compulsive disorder, but the two problems can certainly co-exist in the same person. Some treatments are good for both problems.
OCD. OCD is obsessive compulsive disorder, which is comprised of obsessions (repeating unwanted thoughts) and compulsions (ritualistic behaviors to help deal with those thoughts) such as washing hands repeatedly, constantly cleaning, checking locks, and other similar behaviors. Often the emotions behind OCD are based in fear and/or anger that is unresolved and even unverbalized.
Depression/OCD. Not likely, but the reverse is very possible, since ocd is an anxiety disorder.
Sometimes. Anxious ruminations & agitated depression can certainly present with racing thoughts. I can't think of any reason why ocd might not somtimes present similarly.