Depression can occur as the result of unresolved grief issues after losing a loved one, or following other major changes such as divorce, financial struggles or experiencing a natural disaster.  Depression can sometimes tend to run in families as the biochemical effects linked to depression can be inherited much like we inherit heart disease, diabetes, eye color, etc. 

Anxiety symptoms can occur from overuse of caffeine, or result from a medical diagnosis, or a side effect of certain nutritional deficiencies or even from certain medications.  Some individuals begin experiencing anxiety after multiple significant stressors have occurred, or following other major changes such as divorce, financial struggles or experiencing a natural disaster.