The app, which would activate when it recognized the user's voice, would provide the patient and psychologist a more complete record of changes in emotion and mood, allowing the patient to get a better sense of their emotional triggers.

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So anything that disrupts sleep is very likely to worsen symptoms, leading eventually to the types of rapid changes in mood that are known as "rapid cycling" and that represent such an ominous sign for the long-term prognosis of bipolar disorder.

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Willful, flirtatious and feisty, Katie is prone to mercurial mood changes that result in outbursts of impatient anger, fear or sudden realization, as she struggles to make decisions and find her purpose in life.

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"Whenever you are about to get in the dinghy to take photos of the boat sailing, your mood changes, " he said.

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Lying behind Ms Verdonk's decision are two changes in the Dutch mood since fears over the compatibility of Islam and liberal democracy reached a peak in 2004.

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Dr. Bollen and his colleagues, for example, found that the millions of Twitter messages sent via mobile phones and computers every day captured swings in national mood that presaged changes in the Dow Jones index up to six days in advance with 87.6% accuracy.

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