Mood disorders -- major depression, bipolar disorder, and dysthymia -- frequently recur; they affect one in four people during their lives. At Sunnybrook, 75% of inpatient admissions are due to mood disorders. Mental health telemetry (MHT) lets patients in the community use cell phones to track the severity of their mood symptoms over time, and enables clinicians to view these symptom ratings in real-time. Evidence suggests that MHT is better for detecting exacerbations of illness earlier than standard clinical practice alone. In this study, we will assess if MHT can reduce re-hospitalization rates in previously-hospitalized patients with mood disorders.