Bipolar disorder is thought to affect three per cent of all people and it's possible Britney Spears is among them.

She has pretty violent mood swings - which can be the case with sufferers.

The disorder basically affects the way the brain functions. In extreme cases, sufferers go from feeling suicidal to thinking they're so successful they could buy Australia.

During the up phase of the mood swings, sufferers can be highly energetic and productive. Winston Churchill was bipolar which might just have helped win him the war.

But for most people, it's a very tricky condition to live with.

It isn't caused just by one gene or other, outside events can also be a trigger, such as stress, instability, or perhaps a disordered, celebrity lifestyle. But it can be treated fairly easily.