A dip in mood is often attributable to something specific but there are times when a sudden low mood or extreme gloom happen out of the blue with no obvious cause. This mood doesn't lift with any amount of reasoning or will power. Some people experience this more than once and, although they recognise it when it happens again, they find it so overwhelming that all they can do is wait for the gloom to lift of its own accord. The mood itself is unpleasant enough and the feeling