OCD & depression. Ocd and depression quite often coexist in a person. It may not be all that important to figure out which influences which since they might be equally influencing each other. But the continuous stress a person endures due to her/his OCD might trigger depression, which in turn may worsen the symptoms of the ocd. For some that have ocd, the depression may actually cause them to be more depressed.
Yes. When people are deeper into depression they have a tendency to go to the things that give them comfort. These are usually features of their OCD issues.
OCD. Quite likely; I cannot see how the symptoms of OCD would remain unimpacted by depression. Usually OCD has its emotional bases in fear or anger, and depression could aggravate symptoms easily.