This person may obsess about germs or dirt. In order to stop these thoughts they wash their hands. When the thoughts return they wash their hands again. These compulsive actions can become ritualized. Persons with OCD may believe that they must turn the light switch off exactly seven times in order to be certain that is really off.
Obsessive thinkers can get paranoid under stress.
It is actually the extreme end of thinking too much about things. If you think and think and think about something, you eventually think things are happening that are not really happening. Reducing or managing the stress can eliminate the paranoia in most cases. OCD is presently treated with antidepressant medications and cognitive-behavioral psychotherapy. Some research suggests that outcomes are better if both of these techniques are employed.