Hi Rumination is a symptom of depression in most cases but it may be related to other diagnoses as well including anxiety or OCD. The treatment depends upon the underlying cause and severity of that underlying condition. If the underlying problem is moderate to severe in nature then psychotherapy alone will not be helpful and in that case you have to take medication as well . Hope this clarify your concern. Thanks and regards.

Ruminations are of two types predominantly. Obsessive ruminations which are seen in OCD and anxious ruminations which are seen in depression as well as anxiety disorders. Hence, detailed evaluation is required to understand the underlying cause. Treatment depends upon the underlying cause and severity of symptoms. Usually mild symptoms get improved by psychotherapy, but if they are severe enough that your routine is getting disturbed, you probably need psychotherapy as-well as pharmacotherapy. Best wishes

Just on the basis of one symptom ( rumination) one can't make a diagnosis. Detailed history is needed to reach any conclusion and help your problem. Best of luck.