Bereavement (i.e., serious mourning due to the death of a loved one) is not clinical depression because it is bereavement. In other words, it is obvious that a loved one's death precipitated one's bereavement. But nondeath losses can also precipitate serious mourning, as Susan Anderson describes in her fine book THE JOURNEY FROM ABANDONMENT TO HEALING (2000).
However, it strikes me that clinical depression, a form of mental breakdown, should be understood as a signal that the person needs to experience serious mourning in a healthy way, if this is possible for the person to experience. Similarly, the symptoms of post-traumatic stress syndrome (PTSD) should be understood as signals that the person experiencing the symptoms of PTSD needs to experience serious mourning in a healthy way, if this is possible for the person to experience. No doubt certain other kinds of symptoms should also be understood as signals that the person experiencing the symptoms needs to experience serious mourning in a healthy, if this is possible for the person to experience. But serious mourning in a healthy way is a powerful experience. So when the symptoms are already showing that ego-consciousness is being overpowered, the first order of business for the individual person should be to work out a suitable containment pattern, which usually involves the help of one or more other persons such as psychotherapists and Exquisite Witnesses, to use J. Shep Jeffreys' term in his book HELPING GRIEVING PEOPLE -- WHEN TEARS ARE NOT ENOUGH: A HANDBOOK FOR CARE PROVIDERS (2nd ed. 2011). By working out a suitable containment pattern, the individual person may be able to develop the inner strength in his or her ego-consciousness to undertake the arduous and at times perilous work of serious mourning.
The most famous imagery that I know of for containment occurs in the ODYSSEY when Odysseus is tied to the mast of his ship with his ears plugged as his ship navigates Scylla and Charybdis. Navigating your way through Scylla and Charybdis is a perilous journey.
In real life, President Abraham Lincoln did undertake the work of serious mourning while he was in office. But it remains to be seen if President Obama will follow President Lincoln's example and undertake serious mourning while he is in office. For understandable reasons, President Obama may prefer to work out a suitable containment pattern instead. After all, President Lincoln was assassinated. For understandable reasons, President Obama may prefer not to run the risk of being assassinated if he can help it.
Unfortunately, we do not understand how to help people experience serious mourning in a healthy way. Nevertheless, by definition, serious mourning in a healthy way is a containment experience that is comparable to the containment experiences that babies need to experience when they are distressed. By definition, containment experiences help us contain our abandonment feelings. When individual persons voluntarily seek help through psychotherapy, they are usually seeking help in establishing a containment pattern in their lives that will enable them to cope more effectively with their abandonment feelings. At times, containment is the best way to proceed, especially if containment helps the individual person develop inner strength. Serious mourning in a healthy way requires a certain amount of inner strength, because mourning can be an overpowering experience leading to a mental breakdown. Serious mourning involves what C. G. Jung refers to as legitimate suffering.
J. SHEP JEFFREYS ON GRIEF WORK
As a result of my own experience of bereavement, I started reading works by other people about their own personal experiences of bereavement such as Joan Didion's book THE YEAR OF MAGICAL THINKING (2006). In addition, I started reading works in the professional literature about loss and mourning, including Freud's famous essay "Mourning and Melancholia" (1917). Incidentally, if you are going to read only one thing about serious mourning, read Freud's essay. There's a fine mind at work in that essay.