Intensity and duration of these feelings distinguish a normal level of stress from a psychological condition, Kleiman said.

CNN: Postpartum depression: When moms feel out of control

However, Britney is said to have a psychological condition, such as bipolar disorder, that justifies the continued need for conservatorship.

FORBES: When Will Britney Spears Be Free Of Conservatorship?

He said up to nine million people suffer from the psychological and physiological condition.

BBC: One in five 'suffers banking phobia'

Whereas people with "regular old depression" tend to be highly vulnerable to psychological stress, one way of thinking about bipolar disorder is that it is a condition of extreme sensitivity to the circles of time.

CNN: Can keeping a routine help control bipolar symptoms?