Source:: http://elifesciences.org/content/3/e05105
https://twitter.com/DrMMuehlbacher/status/572140865612869632

In mammals, there are different internal clocks. One of them has been know for a longer time and runs a 24-hour cycle. In depression, mania and schiziophrenie, this cycle is often disturbed,

New findingas indicate an ultradian clock with a circle of only 4 hours which operates independently and regulates motolocor acitivity. In healthy subjects. it is synchronized to the 24-hour circadian clock and is governed by rhythmis release of dopamin in the striatum.

Even for lays and at a first glance, a 4 hour rhythm is not completely unknown:

getting up at 8(7) and breakfast
work for 4 hours then break and have lunch
work for four more hours (maaybe snack), then relax and go home
4 hours private time/ family – it is now 8 pm.
slowly begin „evening routine.
4 hrs later at last: fall asleep (at the latest)
4 am: awake early, go back to slepp if possible
8(7) start from the beginning…

This rhythm is synchronized with dopamine release in the striatum and, under healthy conditions, is synchronized to the 24-hour clock.

However, too little or to much of dopamine may change the harmony.

Too much dopamine (as in mania an schizoprenia ) may lead to an increase of the „ultradian“ circle to a 48-hour circle. this phenomenon is well known in some schizophrenic and manic patients.

On the other hand, blocking dopamine (which is what many anipsychotic and antimanic drugs do) shortens the circle.

In addition, psychoeducation focussing on a stabilization of circadian rhythms, may prove to be beneficial this way.

In the future, new medication and other treatments which focus on re-synchronization of ultrdian and circadian rhythms may open a new avenue to treating various psychiatric disorders.