Clinical depression is a complex condition and it is often caused by a combination of various factors.
Having experienced some 12 or more relapses of clinical depression which usually lasted some 3 to 6 months or longer, I know by experience how painful, confusing and difficult it can be.
The love and support of our loved ones are very crucial. After my diagnosis of proneness to Bipolar Disorder or manic-depressive illness last year, I began to read extensively about bipolar disorder and clinical depression.
My condition alternates between mania and clinical depression. Besides medical help, I actively read and use other coping strategies.
I have found that reading and equiping myself with the necessary knowledge and coping means is very crucial in getting better and maintaining wellness so that I can be functional and be a useful person in my society. It is helping me to manage my condition better. I am learning to identify early symptoms of possible relapses or early signs of worsening symptoms. I am learning what can make my condition better or worse. I am learning to do what is necessary to get better or prevent my condition from worsening.
I also share articles that I have found useful with my family and friends in order to enable them to understand my condition better and know how best to relate to me and help me in time of need. I also hope these articles will help them in their relationship with other family or friends who may suffer from similar condition.
It is only by knowing the symptoms can we know if we or our loved ones are suffering from mental illness, and so seek appropriate help. Many people suffer varying degrees of depression without knowing it, because they do not recognise the symptoms for what they are, and so go for years without getting help that is readily available and which would transform their lives.
Sadly, many who have the symptoms of depression, without identifying them as such, reason that, “If I have these thoughts and feelings, I cannot be a Christian!”
I have found the following article on the causes of depression to be very helpful in understanding my own condition and that of others I know of. Hope you will find it useful too.
(These series of 6 messages on "Depression and the Christian" are also available on .pdf, .mp3 and video formats which can be downloaded from the website ofSermon Audio)
DEPRESSION AND THE CHRISTIAN
BY DR. DAVID P MURRAY
(4) THE CAUSES
In previous lectures we mentioned some of the causes of depression. We also noted the complexity of trying to analyse the causes of depression, and concluded that it is often a combination of various factors. In this lecture we will look in a bit more detail at the various causes of depression, and then we will consider some of the cures for depression.
Depression is often divided into two main categories – reactive or endogenous. Reactive depression is usually traced to some obvious trigger – perhaps a stressful life event or unhelpful thought patterns. Endogenous depression is the name usually given to depressions which seem to have no obvious trigger and are often traced to genetic pre-disposition. For no obvious reason, the brain chemistry becomes unbalanced and a person becomes depressed. However, this distinction between reactive and endogenous is not as clear-cut as it once was, as skilled investigation of many so-called endogenous depressions will often reveal a “trigger event”, though a genetic pre-disposition may mean that the trigger is relatively small. We will consider four triggers of depression: stress, psychology, sin, and sovereignty.
When you stretch a piece of elastic, you can often extend it to two or even three times its size. However, the further you stretch it, the greater the tension on the rubber, the less flexible it becomes, and the greater the danger of it eventually snapping. Like rubber bands, we are all “stretched” from time to time. We are stretched by life events, which we have little control over, and by our lifestyle which we do have considerable control of. Let’s look at each of these stretching forces.
a. Life events
Life events include marriage, moving house, exams, bereavement, illness, unemployment, birth of children, etc. Each of these events put a strain upon us, to one degree or another. When we are “stretched” in this way, our body and brain chemistry changes, and one of the results is often a dip in or lowering of our mood. This is normal. And, as the stressful events pass, our chemistry usually returns to normal along with our mood.
Sometimes, however, these stressful experiences can continue over a lengthy period, or they can occur one on top of another, or they can affect us more seriously than other people. The result is that our brain chemistry remains abnormal and so also does our mood. We just can’t “pick ourselves up”, no matter how many people urge us to. This is depression. At the very worst, like an elastic band, we can “snap”, sometimes unexpectedly. This is what some call a “nervous breakdown”.
Changes in brain chemistry greatly affect our ability to think and feel in a balanced way. Stressful events make our minds go into overdrive, exhausting and depleting the chemicals we need to think and feel in a normal and helpful way. Think of a computer with too many programmes open and working at the same time, and how this slows down all the processes until eventually the machine “crashes”.
While we have little if any control over life events, we do have substantial control over our lifestyle – the proportion of time and energy we give to work, socialising, shopping, travelling, recreation, exercise, rest, sleep, etc. Much of the increase in depression and anxiety today is largely the result of an unbalanced lifestyle where people are on the one hand working too hard and spending too much, and on the other hand are exercising, resting, and sleeping too little. This deliberate overstretch
beyond our capacities and abilities is not glorifying God in our body and spirit (1 Cor.6:20). It is also in breach of the sixth commandment which requires us to take “all lawful endeavours to preserve our own life” (Shorter Catechism 68). The effects and result of a stressful lifestyle will often be the same as that of stressful life events – depression.
2. Psychology (the way we think)
In Lecture 3 we looked at 10 false thinking patterns which contribute to depression. It cannot be emphasised enough how vital it is to learn to recognise these unhelpful thoughts by prayerful self examination. It is also important and useful to note that some of these habits of thinking may be involuntarily absorbed or learned in early life and so may be deeply ingrained. When we feel down, or when we are stressed, these latent false thinking patterns tend to occur more frequently and tend to dominate. This can often lead to depression, worsen an existing depression, and, if persisted in, make recovery from depression so much harder. Sometimes, the Church can reinforce or add to false thinking patterns by over-emphasis on the negatives in the Bible and in people’s lives, or by setting standards of commitment which may discourage or depress those who are unable to attain them.
A non-Christian may be depressed because of their sin, in which case the cure is repentance and faith in Jesus Christ. Sadly, many depressed unbelievers are being treated with chemicals when what they need is conversion. If you are unconverted and depressed then seriously consider whether your depression is related to a guilty conscience and conviction of sin. If so, then what you need is repentance from sin and faith in Jesus Christ. There are many Christians who will testify that this was the key to relieving their depression.
While sin may be the last thing an unconverted person may think is causing their depression, the opposite is true for Christians. When a Christian becomes depressed, there are often spiritual consequences, and so the depressed believer jumps to the conclusion that there is also a spiritual cause – usually their own sins or hypocrisy or failures of one kind or another. Skilled and experienced Christian pastors, doctors, and psychiatrists unite in affirming that depression in Christians is not usually caused by problems with their spiritual life. In Christians, depression is usually caused by stressful life events and lifestyles, or unhelpful thought patterns (see 1 and 2 above). Here are some sample quotations from various experienced Christian pastors, psychiatrists, counsellors, and doctors to prove this point:
“For Christians, depression hardly ever has a spiritual cause…In Christians, spiritual
effects follow from the depression, and seldom the other way around.” 
“True spiritual causes of depression are not common. Most Christians with an apparently religious content to their depression in fact have one of the mental/emotional causes rather than a true spiritual cause. I cannot emphasise enough that solely spiritual causes of depression are infrequent in Christians . ” 
David and other psalmists often found themselves deeply depressed for various reasons. They did not, however, apologize for what they were feeling, nor did they confess it as sin. It was a legitimate part of their relationship with God. They interacted with Him through the context of their depression.” 
“We completely agree that there are always spiritual aspects to anxiety and depression (as there are in everything in life for a Christian). However, we see these as being a secondary consequence of the emotional distress that is part of these illnesses. Strong claims that all anxiety and depression is spiritual in origin are unhelpful because they miss the point that the actual problem is anxiety and depression.” 
I emphasise this point again and again because blaming our depression on our sin is not only usually wrong, it is also very harmful. It is harmful because it increases false guilt and deepens feelings of failure. It also makes depressed Christians seek a spiritual solution to a problem which is actually being caused by life events, lifestyle, or unhelpful thinking patterns. However, having said all that, we must still leave open the possibility that the depression may sometimes be the result of specific sin or sins (e.g. Ps.32). The Westminster Confession of Faith says: “The most wise, righteous, and gracious God doth oftentimes leave, for a season, His own children to manifold temptations, and the corruption of their own hearts, to chastise them for their former sins …” (WCF 5.5).
How then does a Christian know if his depression has a spiritual cause or simply spiritual consequences. The Practical Handbook for Depressed Christians puts it like this: “For the Christian, truly spiritual causes of depression usually involve behaviour which the Christian knows to be wrong, but which he still deliberately and arrogantly persists in…I am not talking about repeated sins that the Christian wishes he could control but can’t…but a deliberate and continued rebellion against God….” 
One final cause of depression in the Christian is the sovereignty of God. Hard though it may be to accept, the ultimate cause may be, “It pleased God.” This however is not some sheer arbitrary, sadistic and pointless infliction of suffering. Not at all. God has wise and loving motives and aims in all His dealings with his children. The Westminster Confession of Faith proposes another reason why God will sometimes allow his children to descend into the depths of depression. It is “ to discover unto them the hidden strength of corruption and deceitfulness of their hearts, that they may be humbled; and, to raise them to a more close and constant dependence for their support upon Himself, and to make them more watchful against all future occasions of sin, and for sundry other just and holy ends (5.5)".
A well known example of this is Job. A lesser known example is Hezekiah. “God left him, to try him, that he might know all that was in his heart” (2 Chronicles 32:31). This does not mean that God actually left Hezekiah. God will never leave nor forsake His people. This, then, is not an objective leaving, but a subjective leaving. God withdrew Himself from Hezekiah’s spiritual feelings, so that he lost his feelings of God’s presence, protection, and favour. So, Hezekiah felt God had left him. But God had a wise and loving purpose in this. It was to test Hezekiah and to reveal to Hezekiah what was in his heart when God’s felt presence was withdrawn.
Sometimes we can take God’s presence in our lives for granted. We forget what we might be without him. And so He wisely, temporarily, and proportionately withdraws the sense of his favour and presence to remind us of our state without Him and to lead us to greater thankfulness and appreciation for Him
DrJohnLockley, A Practical Workbook for the Depressed Christian (Bucks: Authentic Media, 1991), 53-54.