If serotonin levels suddenly drop, a migraine may develop. Chronic changes in serotonin levels may also lead to psychological conditions. People with anxiety or panic disorder develop an overwhelming sense of fear or nervousness without any clear reason. This may be so severe that they are unable to function at work or at home. An actual attack can last for several days.
Depression is a change in a person's mood that lasts for an extended period of time.
People with depression often feel sad, alone, or isolated. They also have decreased energy and do not enjoy activities that they would enjoy normally. Stress is the human body's response to outside factors that a person perceives as dangerous, damaging, painful, or which may have a negative impact on the person. Thousands of years ago, human stresses were mostly physical. Today, many stresses are directed toward a person's emotional and psychological well-being.