bipolar depression is a serious mental health condition that causes extreme changes in mood. These mood changes can last for prolonged periods, and the switch between moods can happen very quickly.
People who have untreated bipolar depression rarely enjoy much, if any, time when their mood settles to a normal level, so life can be a constant and exhausting struggle.
The cause of bipolar depression isn’t certain, but research indicates that brain function is different in people who have bipolar depression. It’s likely that genetics plays a part, but there could well be environmental factors at work as well.