This paper addresses the actual role of CSF in the physiology and ethiopathogeny of mental disorders as schizophrenia, schizoaffective disorder and bipolar disorder. Several decades ago the observation that the enlargement of ventricular size was associated with a clinical diagnosis of schizoaffective illness was reported  by first time. Changes in the volume of the cerebral ventricles and therefore the content of the liquid cephalous spinal far beyond the daily physiological variations, are already known in mental disorders, but have only been to date more a curious object of in-depth studies for various reasons. Usually it pays more attention to alterations of the nervous tissue in which volumetric changes are observed in the ventricles. The finding that the melanin molecule has the amazing ability to transform light energy into chemical energy through the dissociation of the molecule of water, such as chlorophyll in plants; the old dogma that the source of energy of the Central nervous system (CNS) is through blood vessels break into a thousand pieces. We now know that the real source of energy of the CNS is the visible and invisible light and the transducer per excellence is melanin, and whose perfect substrate is water. It is, therefore, that the CNS of all mammals has a repeating pattern invariably to be coated inside and out by the CSF that is 99% water, which ensures that the energy substrate source, water for all practical purposes, is constantly in contact with neurons. The brain caesuras allow water getting as much as possible to the most recondite places of the brain. Thereby the source of energy of CNS are the ventricles and subarachnoid space, therefore, the changes in volumetric characteristics of this anatomic regions must be interpreted as significant alterations in generation and distribution of chemical energy.