I think it is a clinical psychologist could use a number of methods to treat someone with a mood disorder, depending on their area of expertise as well as the patient's expectations and preferences. A few examples of different psychological methods include: Cognitive Behavioral Therapy, which can work well for patients with depression, anxiety, or phobias; psychoanalysis, which is a more Freudian approach that focuses on past trauma, the unconscious, repressed memories, subconscious fears or desires, and so on; or, the psychologist might use a combination of different methods in order to fit the needs of their patient. If the psychologist determines that therapy alone is not the right option for their patient, they might then refer them to a psychiatrist, who would be able to prescribe appropriate medication.