In this unit, you learned about ancient civilizations
that existed in Asia and the Americas. What were
the major achievements of each civilization? Of
the achievements that you identified, which do
you think had the biggest significance in world
history? Why?

Explanation:

Research suggests that depression doesn't spring from simply having too much or too little of certain brain chemicals. Rather, there are many possible causes of depression, including faulty mood regulation by the brain, genetic vulnerability, stressful life events, medications, and medical problems.