Obsessions are a symptom of obsessive-compulsive disorder (OCD). Obsessions are defined as recurring, persistent thoughts, impulses, and/or images that are viewed as intrusive and inappropriate. Obsessions often cause considerable distress and anxiety.
Obsessions, as seen in OCD, are not just worries about real-life problems, and people will try (often unsuccessfully) to ignore or "push away" these recurrent thoughts, impulses or images. Finally, in OCD, people recognize that these obsessions are from their own mind (and not delusions like what might be seen in someone with a psychotic disorder).
Although obsessions are a symptom of OCD, they are also seen in other anxiety disorders, such as PTSD.

