Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter 12
Chapter 13
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Adaptation has a price. Sometimes the cost is too high, and the brain fails to cope. Persistent stress, such as a job with too much pressure but too little power of decision, predisposes us to illnesses such as duodenal ulcer, diabetes, heart disease. All are consequences of the cost of demand. Stress is translated into illness by the brain, since this is how you become aware of the demands on you, and how you formulate your response to them. But the brain itself may succumb to stress, and this is the subject of this chapter……..
Nearly everyone has, at sometime in his or her life, a stress such as a bereavement, loss of a job, the breakdown of a relationship. Painful as these are, most people get over them in time. But not everyone. In a small proportion of such people, such an adverse ‘life event’ (as it’s called) is followed by an episode of mental illness, particularly depression (major depressive disorder: MDD). The brain has failed to cope with, or adapt to, this serious stress. Depression is a major health problem throughout the world. It used to be called a ‘mental breakdown’. Despite all the defences we have against misfortune, sometimes it
overwhelms us. Our adaptive power has
failed us…..Attempts to understand how depression is associated with brain function are a good example of the way that two major strands of information about any illness try to come together. On the one hand there is knowledge about the neural basis of emotion. This is derived mostly from experimental studies on the brain. On the other, there is understanding depression as a clinical phenomenon, related to mal-adaptation. This comes from observations on patients, and resulting experience of the variety and outcome of depression. First, of course, we have to accept that the first strand is relevant to the second. Is depression a disorder of emotion? Clinicians don’t often talk about ‘emotion’ but of ‘mood’. Depression, most psychiatrists agree, is a disorder of mood: that is, it is the presence of an abnormal, inappropriate, incapacitating mood state. Experimental psychologists hardly ever study ‘mood’ but something they call ‘emotion’. Clinical psychologists, in the other hand, measure mood state, or assert that they do. Are they all talking about the same thing? …..
…. If depression is a condition of extreme, but normal, ‘sadness’ but in an ‘abnormal’ (that is, inappropriate) situation, then our search for its cause will focus on why an extreme emotional state is triggered in the wrong circumstances. Since how we react has to be ‘adaptive’, that is, fit in with our requirements to cope successfully with whatever demands life puts on us, to be overwhelmed with the ‘wrong’ mood would be maladaptive, and impair normal function…..
But there is another possibility. Depression is common and strikes regardless of class, gender , intellectual ability and education. This doesn’t mean, by the way, that these factors don’t influence the chance of its occurring. But it can happen to anybody. Including some very articulate writers, who have told the rest of us what it’s like to be depressed......
We should not forget that other mental illnesses may also be associated
with intolerable stress. An event that threatens life itself and spells
extreme danger may be followed by a disorder graphically and accurately
called ‘post-traumatic stress disorder’ usually abbreviated
to PTSD. Earthquakes, war, fires, rape and car accidents may result in
PTSD, a condition that has some unusual and characteristic
features. To you and me, the sound of a helicopter passing over
head may simply be a minor irritant. But there are those who were in
Vietnam during the 1960s-70s in whom this innocuous sound may provoke a
very different, and altogether more damaging reaction. Suddenly,
they are back in that forest clearing, the sound of the helicopter
deafeningly close, their comrades lying mutilated round them, expecting
any moment to feel the bullets tearing through them too. Unspeakable
terror grips them now, as it did then….What do we know about the risk for depression? It’s been known for quite some time that certain sorts of people seem to have an increased chance of getting depressed after a the severe stress of an unwelcome life event. Not everyone agrees about what these factors are, but in general they fall into three categories: the person’s social environment (their quality of life and the support of friends and partners ), their psychological makeup (for example, their tendency to be rather anxious), and whether they have relatives that have been or are depressed……. But there are some other clues. The first is that women are about twice as liable to get depressed as men. There have been many attempted explanations for this, but it’s striking that this sex difference appears only at puberty. Pre-pubertal children also get depressed (this used to be denied) but the sex ratio is almost one. During and after puberty, it changes. So perhaps the rapid increase in sex hormones at and after puberty has something to do with risk?..... Each morning, cortisol surges into your blood, but as the evening approaches levels go right down. Everyone has a different rhythm: my cortisol may rise a bit higher than yours each day, and yours may vary from day to day. So some people have characteristically somewhat higher ‘high tides’ than others. Now here’s the striking fact: women and adolescents with higher morning levels have a greater risk of becoming depressed after an unwelcome life event. The daily higher levels of cortisol seems to sensitise their brains to react to adversity by depression. Cortisol seemingly pushes them nearer the brink, but the life event pushes them over the cliff………
Recently, scanning the living brains of depressed people has shown a small over-active area at the front part of the limbic cortex. It’s quite close to the orbitofrontal cortex (see Chapters 5 and 10) – the region at the base of the front of the brain that has so much to do with emotional responses. But what this means – is it the ‘cause’ of depression or a consequence – and what the over-activity signifies - are still mysteries. Another plausible site is the amygdala. As we saw in Chapters 4 and 10, there’s a lot of evidence suggesting that the amygdala has a central role in emotional responses, particularly (but perhaps not exclusively) those that are learned. Some evidence from imaging studies on depressives’ brains also points to the amygdala.
Scientific and literary quotes.