There are many medications for treating bipolar disorder, so a psychiatrist, who is best qualified to identify which drugs work best for a specific patient, should oversee treatment. A psychiatrist is trained as a medical doctor (MD or DO).
Psychologists and some mental health counselors (Ph.Ds and PsyDs) can provide psychotherapy, or talk therapy, another critical part of treatment. Through therapy, people can develop coping methods that prevent long periods of illness, extended hospital stays, and suicide.
The bipolar spectrum is a term used to refer to conditions that include not only bipolar disorder as traditionally defined (that is, clear episodes of mania or hypomania as well as depressive syndromes) but also other types of mental conditions that can involve depression or mood swings without manic or hypomanic episodes -- including some impulse control disorders, anxiety disorders, personality disorders, and forms of substance abuse. Some psychiatrists find the "bipolar spectrum" concept to be...
WebMD Medical Reference: "Bipolar Disorder (Manic Depressive Disorder)" and "Effects of Untreated Depression."
WebMD Assess Plus: Bipolar Disorder Assessment. National Institute for Mental Health: "Step-BD Women's Studies."Massachusetts General Hospital Bipolar Clinic & Research Program. MedicineNet.com: "Bipolar Disorder (Mania)." American Psychiatric Association: "Practice Guideline for the Treatment of Patients With Bipolar Disorder."