Can a break up be the cause of major depression or is it more likely merely a catalyst for the depression but not the underlying cause?

When things hurt humans they can go into a depressive slump and why shouldn't a person feel this way. It's normal, but not normal when a person goes on for months and months without trying to move on. We have become a society of pill poppers to try to stifle every emotion one has. The break-up causes sadness and depression and it's a grieving process much like losing a loved one by death. In time the hurt will slowly ebb and it will take strength for the person to move on, but we all have too. There is always hope and there is always that right person that one will meet. I believe we have to go down some bumpy paths in our lives to get to where our true happiness lies.