I truly believe that humans are experiencing mental health issues (also physical) on a scale unprecedented and passed on via DNA in our mixing populations . I think this is down to a few different scenarios (just my personal belief). Our DNA that took unknown amount of years to develop on continents separated from travel in history, developed in different climates (temperature), different latitudes (pressure) radiation exposure locally (from within planet or external) and the foods that are eaten in their local environment and cultures.
All these factors created a stable genetic species that survived well in their environment. Once humans started to travel continents and to isolated places on the planet, genetic mixing started to take place. This is where detrimental health problems started, as the offspring dependent on where they lived and the foods they were consuming started to alter imbalance in the chemical makeup of their new DNA structure. This gradual decline of essential nutrients and elements needed for their cells to operate started to become apparent generations down the line, coupled with some natural organic wildly grown vegetation and fungus that has been omitted from our diets by the governors and powers of the lands, making certain substances illegal have also taken things out of our diets that played a big part in our evolution. This in turn lowers chemical reactions within our finely tuned biological systems creating unlimited diversity of damage within our cell structures. To make this relevant to this post a few chemicals that are creating imbalance in our brains like serotonin, dopamine and all the rest of them, are creating problems with our thought processes, creating what psychologists call mental health problems.