Bipolar disorder or manic-depressive illness is a mental disorder characterized by abnormal mood shifts, as well as fluctuations in energy, activity levels and the ability to complete everyday tasks. Bipolar is a serious mental illness that can damage relationships, career prospects, academic performance, and can even lead to suicidal tendencies. A patient with bipolar disorder has severe fluctuations in mood (poles) - from depression to mania. Usually, moods are normal in between the peaks and troughs.