Things that can cause this are (but not limited to):
- some kind of brain injury (a knock or a fall, punch, heading a football etc.)
- a psychotic illness, causing or including a psychotic depression (hallucination and/or delusion)
- brain disease, tumours, meningitis, TIA, stroke etc.
- viral or bacterial infection (as well as in the body/organs, dental or nasal problems have also been linked)
- autoimmune diseases
- mineral or vitamin deficiency
- genetic factors
So, adopting an attitude that all depression is equal, as in a psychological/mental condition, is naive to the extreme. As is the idea that one type of treatment will work for everyone. Some therapists (including hypnotherapists) believe there's a one type fits all treatment. Others believe all you have to do is to focus on the future and by default ignore the past. Some have actually said, "the whole world has got it wrong," an over generalisation if ever I heard one! Obviously taking a view that treating depression with medication doesn't deal with the problem or its root cause. By default implying, that you have to get to that root cause (which is deemed to be psychological), in order to effectively treat depression. A rather arrogant and disrespectful point of view for anyone, even more so coming from a therapist! In many cases, the 'root cause' isn't that obvious, if at all. Also, because anxiety and depression are progressive disorders, there often isn't just one 'root cause' but rather a succession of cumulative events. Hence why it can be a complex condition to treat.
Of course, there is a small amount of truth in the views other therapists quote. This is because, for some client's, future posturing can work, as can treating the psychological event that caused the depression (the root cause). However, what you cannot afford to do, is to make an assumption, based on ignorance, on how to treat the client in front of you. You have to perform an exhaustive investigation into the probable, likely or definitive cause(s) of their depression (assuming it has been clinically diagnosed)! For the client whose past is identified as most definitely/probably involved (a root cause), there is often value in some type of regression therapy. And for those, where there is evidence of brain trauma, illness or disease, a very different methodology of hypnotherapeutic intervention is needed! Medication could also justifiably be indicated as being a good option! Not necessarily in isolation but rather in tandem with hypnotherapy.
Therefore, one of the most important steps in treating depression is to first get to know the client by doing a thorough and detailed case history. You simply cannot second guess the nature of such a serious medical condition as a major depressive disorder or any of its variants. Nor can you assume, that what worked for one client, will work for every client. Equally, you cannot concur with many of the assumptions that abound, some of these assumptions I cover below. Each treatment is often as unique as each client and discovering all that takes a little while. Essentially it evolves over a few sessions with some therapeutic interventions are added along the way. So, what evolves is a progressive and incremental form of healing that often begins to slowly unfold.