What often blocks the ability to generate adequate energy for brain cells to function well is excess stress. Excess stress affects our ability to process thoughts and emotions and it is known that 90% of low mood is due to stress. Other than difficult life situations, there are other chemical or physical types of stress that cumulatively can make stress even worse. Things such as unhealthy food, environmental toxins, reduced daylight in the mid fall through winter time and excessive strenuous athletic activities are all examples of stress. These examples can result in overproduction of the stress hormones such as adrenaline and cortisol. Stress hormones, when present in excessive amounts over a long period of time, deplete the energy reserves of the cells of the body, leading to mental and physical fatigue and to low mood.