Bipolar disorder is a complex, recurrent, severe and potentially lifelong mental illness. The peak age of onset is 15-19 years, with most cases developing before the age of 30. It is crucial to distinguish bipolar from unipolar depression not only as an essential starting point for appropriate treatment and risk management, but also to avoid antidepressant monotherapy which can exacerbate the frequency and severity of mood symptoms and cause resistance to appropriate medications.