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Living a structured life with regularly established meal times and early bedtimes can improve your physical and mental health, researchers have found.

They say that as well as a 24 hour cycle, our bodies rely on a four hour cycle known as an ultradian rhythm.

Upsetting this can cause major problem, they say.

Researchers say that as well as a 24 hour cycle, our bodies rely on a four hour cycle known as an ultradian rhythm.

Kai-Florian Storch of the Douglas Mental Health University Institute and McGill University, led the study, which has been published in the online journal eLife.

Our daily sleep-wake cycle is governed by an internal 24-hour timer, the circadian clock.

However, there is evidence that daily activity is also influenced by rhythms much shorter than 24 hours, which are known as ultradian rhythms and follow a four-hour cycle.

'Ultradian rhythms with periods ranging from one to several hours have been linked to various aspects of mammalian physiology, the researchers wrote.

'Usually superimposed on the 24-hr diurnal or circadian rhythm, ultradian oscillations have been observed in the context of locomotion, sleep, feeding, body temperature, serum hormones, and brain monoamines in species ranging from fruit flies to humans.'

These four-hour ultradian rhythms are activated by dopamine, a key chemical substance in the brain. 

When dopamine levels are out of kilter - as is suggested to be the case with people suffering from bipolar disease and schizophrenia - the four-hour rhythms can stretch as long as 48 hours. 

With this study, conducted on genetically modified mice, Dr. Storch and his team demonstrate that sleep abnormalities, which in the past have been associated with circadian rhythm disruption, result instead from an imbalance of an ultradian rhythm generator (oscillator) that is based on dopamine.

These four-hour ultradian rhythms are activated by dopamine, a key chemical substance in the brain, and are the reason we eat three regular meals a day.

'Collectively, our results provide strong evidence that a dopaminergic ultradian oscillator (DUO) driving rhythms of behavioral arousal is continuously operative in the mammalian brain,' they say.

The team's findings also offer a very specific explanation for the two-day cycling between mania and depression observed in certain bipolar cases: it is a result of the dopamine oscillator running on a 48-hour cycle. 

This work is groundbreaking not only because of its discovery of a novel dopamine-based rhythm generator, but also because of its links to psychopathology. 

This new data suggests that when the ultradian arousal oscillator goes awry, sleep becomes disturbed and mania will be induced in bipolar patients; oscillator imbalance may likely also be associated with schizophrenic episodes in schizophrenic subjects. 

The findings have potentially strong implications for the treatment of bipolar disease and other mental illnesses linked to dopamine dysregulation.