Among other things, neuroplasticity means that emotions such as happiness and compassion can be cultivated in much the same way that a person can learn through repetition to play golf and basketball or master a musical instrument, and that such practice changes the activity and physical aspects of specific brain areas.” 
― Andrew Weil

Over the last twenty years it has become clear that the condition we call depression does not have one single cause or presentation. The accumulation of evidence shows that some types of depression are either brought about, or sustained by the way we think and interact with our world. Recent research suggests that an inflammatory response, brought about by our modern lifestyle, may also contribute to the development and persistence of such states.

The evidence also shows that our genetic makeup contributes to our risk of developing a depressive disorder. However, the presence of this genetic influence does not mean that depression is a purely genetic disorder.

We all receive a unique combination of genes from our parents. Genes act through the instructions they provide for the way our bodies are put together, and how our various physiological systems function at a biological level. This is true for our physical and mental attributes. Our genes give the instructions for making a human being with our specific characteristics – red hair, blue eyes, brown skin, prone to anxiety, easily startled and so forth.

What we inherit are tendencies for our biological systems to respond in certain ways, to differing stimuli and conditions in our environment. Genes act in a probabilistic fashion, giving us a variable degree of risk for many different ways of behaving or functioning.

So we will all have our own unique pathways, some of which may use a different neurotransmitter compared to someone else. Where I use serotonin you may use noradrenaline for instance.

These inherited tendencies are not always negative.

for those of us who do develop depression there is an interaction between our lives and our genes

Only occasionally does the presence, or absence, of a specific gene always cause a disorder, Huntington’s Chorea and Cystic Fibrosis are examples of a single gene bringing about a specific disorder in all of those who have it.

For most disorders which have a genetic component, it takes a combination of several different genes, interacting with each other and with triggers in our environment, to cause a recognisable problem. Diabetes would be a case in point. Although the disorder runs in families the risk of developing the condition is not 100%.

Heritability is a measure of how much our genes contribute to the development of a disorder. For type 1 diabetes it is about 80%, for type 2 it is about 20%, the remaining risk is down to individual differences in our lifestyle, or exposure to pathogens in our environment.

The genetics of depression is similar to that of diabetes. Heritability is at most 40 to 50%. It is not clear if this means that half the risk is always genetic, or if sometimes it is 100% and sometimes 0. Either way, for those of us who do develop depression there is an interaction between our lives and our genes. The more severe the depression, the greater is the apparent contribution from our genes. This could be due to a stronger response to an environmental trigger or greater susceptibility to a lesser trigger.

Some of us have a lot of these “at risk” genes while others may have few or none at all. There is an additive effect, the more genes that we have, the more easily we tend to get depressed under particular circumstances. Some folks with a very high genetic loading never get depressed, while others with a very low genetic risk, exposed to adverse life circumstances, do so much more easily.

Adverse life events that occur during our childhood have a greater impact than those that occur later. Childhood is a time when we are learning and developing our own personal way of interacting with the world. Poverty, bullying, abuse, early parental death, are just a few of the events that can increase our vulnerability to depression. They exert effects on how our brain develops and processes information. The sense we make out of this information, and how we consequently learn to think and feel, can become distorted so that we reach the wrong conclusions about ourselves and the world.

The good news in all this is that the brain is constantly changing and making new connections. This means that we have a good chance of reducing our risk of depression, by changing our lifestyle to reduce, or even eliminate, such social and psychological risk factors. In other words if we can use this plasticity to change the way we think and respond to the world, we can maintain a better level of mental health. We can deliberately choose to use “healthy” ways of thinking and behaving to support, or improve our mental health. Although this may not be as easy as it sounds.

This is the premise behind the positive psychology movement. Here the focus is on helping people to live healthier and happier lives. There is an added advantage that it will also reduce the risk of problems arising in the first place. The historical approach has been to concentrate on fixing things once they have become broken.

These principles can also be used to reduce the frequency of recurrent depressive episodes, or to try to prevent the condition arising in those who have a higher than average genetic loading.

Much research is continuing into brain plasticity. This is the ability of the brain to change the way it works, by effectively rewiring some of its circuits so that they function differently. Our brain contains some 100 billion nerve cells each of which can make up to 100,000 connections with other cells, including itself. These connections can be excitatory or inhibitory, resulting in a highly complex, layered structure, made up of many different circuits, that not only controls how our bodies work, but also generates our mind and consciousness.

Brain plasticity is part of normal development. The growth of the brain during childhood is due to an increase in connections between cells rather than an increase in their number. Every time something happens our brain cells make new connections. If things happen a lot, these connections last longer and so can become a short cut for the way our brain sends and processes information.This means that under similar circumstances in the future it is much more likely that we will behave in an almost automatic fashion to the same or similar stimuli. Should adverse experiences have intervened in this process it is likely that we will learn to behave in ways that are unlikely to be helpful, and might well make our situation worse.

The good news in all this is that the brain is constantly changing and making new connections

In our emotional life, this is often seen with the things that make us anxious. We just have to think of something and this can set off a strong emotional response. This uses our “fight or flight” pathways, designed to keep us safe from danger. Much of the response generated by this emergency system is at an unconscious level, so it often happens before we are even aware of the trigger. This makes it much harder for us to control some things compared to others.

One person’s idea of excitement can be another person’s worse nightmare – just watching what some people do for fun on YouTube, for example, can make me feel quite ill!

If our genetic inheritance and our life experiences come together in an unhelpful way, the result is the development of deeply ingrained ways of thinking and feeling that significantly effect our behaviour and emotions. These pathways behave as though they are “hard-wired”, kicking in automatically before we can consciously influence them. This sets up negatively reverberating circuits within our mind and brain. The result is that we start to ruminate and enter a negative, downward, cognitive spiral. This produces many of the mental and physical symptoms of depression.

One of the main problems with depression, is that by its very nature, it makes it difficult for us to be able to take the necessary steps to change our predicament. It takes away our energy and ability to act,making us feel hopeless and powerless. When we are particularly stuck, or the biological element in our disorder is particularly strong, antidepressant medication has a role to play in lifting our mood enough to allow us to use the psychological and behavioural treatments that have been demonstrated to work.

For mild to moderate depression medication is of little proven benefit, and in these states psychological and behavioural therapies are the most effective interventions, particularly those that help us change how we think, and subsequently react to life. These approaches use the brain’s plasticity to set up new pathways and ways of behaving and thinking.

For more severe presentations, medication and psychological interventions used in tandem, have been shown to be better than using either treatment on its own.

Moshe Bar suggests that positive mood states are a reward system designed to help us use our brain in the most productive way we can. Depression narrows down our thought processes and this leads to rumination, while the cognitive therapy approaches that have been shown to be helpful, are ones that encourage us to widen our cognitive perspective, and to make judgements based on as much information as possible. In other words we should use the evidence that is before us and resist the temptation to jump to inaccurate conclusions.

In this situation it is reasonable to consider that there may be a two-way relationship. Positive mood leads to wider associative thinking; wider associative thinking leads to better mood states.

Evolutionary pressures for survival would favour such a link. The more information that we can process about the environment, the more easily we can detect danger. Our survival would be further enhanced by the ability to use information as widely as possible by making multiple, varied associations with our past experiences. The result of this would be more accurate predictions about the way events are likely to pan out.

Greater predictive ability would reduce our uncertainty about the future, resulting in less anxiety and reduced stress. Anxiety and stress lead us to focus on imminent danger, and to be on the look out for what is threatening in our world. Part of their effect is to narrow our thinking onto the things that might be a threat, switching off the wider net of our thoughts in the name of survival, This response also leads to rumination, where we become moe and more focussed on the negative aspects of the past, and the negative predictions that we might make about the future. The hormones produced by the body in response to acute stress,and which are designed to prepare us for this fight or flight response, are also released under these circumstances. This has longer term adverse effects on our thinking and emotions.

Chronic uncertainty and stress, found in many a modern lifestyle, lead to prolonged stress states with their associated chemical responses. This hormonal and chemical response to danger would usually be short-lived, lasting from a few hours to a day or so at the most. It would also be accompanied by a burst or two of pronounced physical exertion, as we ran or fought for our lives. These responses to chronic stress are considerably prolonged compared to the way they were designed to function in the body.

The relationship between mood and associative thinking is direct, the more associative thinking we do the better our mood is likely to be. Similarly less associative thinking is relevant to the generation of low, depressed mood states and their maintenance. It would therefore be sensible to try and increase the amount of time we spend in associative thinking states. This would help to shift attention away from the triggering events and thoughts on to other, more neutral, or even positive topics.

Some research suggests that the more widely we can spread our thought processes the greater the effect. Faster thinking generates more links and associations. Investigators have found that paced reading can have a positive benefit on mood. This holds true whether the content of the reading is positive or negative in nature.

These findings have important implications for mental health and the treatment of disorder. Rumination can be a very difficult process to change, especially if we use brute force to confront it, yet there is no need to try. Associative thinking and rumination are incompatible.

The secret is to occupy our mind with other stimuli, ones that generate more associative thinking. Exercise, reading, conversation, listening to music are all things that increase our ability to think and feel more widely, pulling together different strands of our thoughts and emotions.

In this way we can use the brain’s plasticity to change how we think and feel, and this will help to stop rumination and so remove one of the common cognitive distortions that leads to depression