There is widespread agreement as to the nature of our emotional needs. The following are fundamental to mental health:

• A sense of security - safe territory and an environment which allows us to relax and develop fully.
• Attention - a form of nutrition. To give and receive good quality attention fuels the healthy development of each individual, family and human group. It is also the means by which knowledge is passed on and cultures grow.
• Sense of autonomy and control - having volition to make responsible choices (When we feel out of control, especially of important elements of our lives, we become increasingly anxious and even depressed).
• Emotional intimacy — to know that at least one other person accepts us totally for who we are, “warts ‘n’ all”.
• Feeling part of a wider community – a sense of ‘belonging’.
• Sense of status within social groups – we need to feel valued by our peers.
• Sense of competence and achievement - which comes from successful learning and effectively applying skills – the antidote to ‘low self-esteem’.
• Privacy - an opportunity to reflect on life’s experiences and consolidate them.
• A sense of meaning and purpose - which comes from both being ‘stretched’ in what we do and think, and being needed.

It is a law of Nature that when a human being gets his or her innate emotional needs met in balanced ways he or she cannot suffer mental illness. Those whose needs are not fulfilled, or whose innate resources are damaged in some way, are the ones who suffer considerable distress and may develop, as a means of coping, mental illness or antisocial behaviours that are a burden to others.

1. The environment the person lives or works in is ‘sick’ and prevents them from getting one or more of their needs met (as in having to endure an abusive dysfunctional family, living in a threatening neighbourhood, working for a bully or without any autonomy).
2. A mis-use of personal resources, the person doesn’t know how to operate their internal guidance system so as to get their needs met.  This is like a learned helplessness when a person has been conditioned to have low expectations of themselves, or when they don’t know how to challenge unrealistic expectations with universal reasoning, or when someone is misusing their imagination by worrying – which precipitates depression – instead of using it to solve problems.
3. Physical damage - the person’s innate guidance system is damaged in some way: perhaps through faulty transmission of genetic knowledge (as in the inability to read context, caetextia, seen throughout the autistic spectrum), poor diet (not getting proper nutriment to the brain), poisoning (drugs, alcohol etc), physical accidents to the brain, or psychological trauma (including PTSD).

• People sink into a depressed mood when their innate physical or emotional needs are not being met and, instead of dealing with this situation, they begin to worry about it — misusing their imagination. All depressed people worry. This increases the amount of dreaming they do, upsetting the balance between slow-wave, recuperative sleep and dream sleep. Consequently they start to develop an imbalance between energy burning dream sleep and refreshing slow-wave sleep. Soon they start to wake up feeling tired and unmotivated. (Depressed and anxious people dream far more intensely than non-depressed people.) This makes them worry even more as they feel that, "something is wrong with me". 
• Depression is a human vulnerability. Suppose we have a setback or suffer some traumatic event that interferes with getting our innate needs met. This arouses negative expectations in the autonomic nervous system — feelings of frustration, being 'stressed', anxious, angry, guilty etc. — but, instead of taking action to bring the arousal down, which is what the autonomic nervous system is designed to help us do, we start to worry even more, going over and over what's troubling us: 'Why did I lose that job?'…"Why do they treat me like this?"… 'What is going to happen to me?'… 'How am I going to pay my bills?' — on and on creating a mountain of negative expectations. This over-stimulates the autonomic arousal system which is why depression is such a strong emotion.   
• All strong emotions focus and lock attention and, with depression, attention stays focused on all the bad things that seem to be happening to us, whether real or illusory. Every little thing we worry about and do not resolve in the day is translated into a bad dream the next night. All these worries have to be worked through in extended and intense periods of dream activity in REM sleep as the brain attempts to rebalance your arousal levels. This upsets the relationship between slow wave sleep and REM sleep.

• Extended dreaming is exhausting, not just because it deprives us of restful and restorative slow-wave sleep (that should make up three-quarters of our sleep time), but also because it stimulates the orientation response. This is a vital pathway in the brain that alerts us to interesting things in the day, generating motivation to act, but it can't do this so well if it has been over-used in dream-sleep the previous night. So, the next morning we awake feeling terrible because we haven't really slept, and we find it much harder to get motivated to get up and do anything because the brain mechanism that generates that interest in life is exhausted as well.  
• Exhaustion on waking and lack of motivation are features common to all depressed people. Because our normal sense that life is meaningful comes from the actions we take, when our motivation levels are low, life quickly comes to seem meaningless. The natural delight we take in being alive and doing things drains away.

To be deeply depressed is just about the most awful feeling we can experience, apart from sheer terror. It can disable anyone. But the topic is surrounded by false ideas: Depression, as experienced by the vast majority of sufferers for example, is not a biological illness; neither is it 'anger turned inward'; it is not a 'chemical imbalance in the brain' and it is not usefully divided into 'clinical depression', 'post-natal depression' and ordinary 'depression'; and is not, in most cases, hard to come out of.

The term 'endogenous depression' is used to describe a low mood that is purely the result of biological factors, such as a brain disorder or neurological dysfunction affecting serotonin, dopamine or other neurotransmitter. Such specific brain damage is very rare.

Note: Depressed or anxious people should not have forms of counselling or psychotherapy that concentrates on the past and encourages introspection or emotional arousal. Research shows this is often unintentionally harmful.