The notion of waterfalls making you happy is often viewed as an “old wives’ tale,” but there may be some truth to it given the so-called “negative ions” pervasive in such environments. The collision of water molecules with each other causes water to be positively charged and surrounding air to be negatively charged. “High concentrations of negative ions are essential for high energy and positive mood,” he reports. “Negative ions suppress serotonin levels in much the same way that natural sunlight suppresses melatonin. Hence the invigorating effect of fresh air and sunshine and the correspondingly depressed feelings associated with being closed in and dark.”ADVERTISEMENT“The atmosphere we breathe normally is full of positive and negative ions,” he adds.