Why is this so? Do we inherit anxiety through our genes, or learn it from those closest to us? Are anxiety levels biologically hard-wired, or the product of life experiences (that is, our ‘environment’)? Over the years, both explanations have been proposed by scientists. In this chapter, we’ll take a look at the evidence and try to answer that perennial question: is it nature or nurture?
The genetic perspective
Everyone is familiar with the term ‘gene’, and most people are aware that genes are involved in the transmission of characteristics from parent to child. Beyond this, however, we may be a little hazy! So what exactly are genes?
Every cell in our body contains 23 pairs of chromosomes, which are structures composed of deoxyribonucleic acid (DNA) and other biochemicals. One of each pair is inherited from our mother and the other from our father. Each chromosome, in every cell, contains thousands of genes – essentially extended molecules of DNA – which contain the biological rules that underlie our development. With the exception of identical twins, everyone’s genetic make-up is different.
How can we tell whether genes are responsible for anxiety (or indeed anything else)? A reasonable starting point is family history. However, although this strategy may highlight a similarity between family members, it doesn’t help us decide whether that similarity (or family aggregation) is the result of genes or environment. After all, families typically share a significant portion of both.
That said, certain types of families provide scientists with an important means of unravelling the gene/environment knot. These families are those that contain twins. Fraternal twins develop from separate eggs (hence the technical term ‘dizygotic’) that have been fertilized by different sperm. Like all siblings, fraternal twins share 50% of their genes. Identical (or monozygotic) twins, on the other hand, result from the fertilization by a single sperm of one egg that subsequently splits into two. As a result, their genetic make-up is exactly the same. If an anxiety disorder, for instance, is more likely to be shared by identical twins than fraternal twins, we can be fairly certain that the difference is the result of genetic factors.
Fairly certain, but not definite because identical twins may have more experiences in common than fraternal twins (although in fact the assumption that the influence of environmental factors is equal for both types of twins seems to hold). Here’s where adoption studies come in. Imagine, for example, that identical twins have been separated at birth and placed with different adoptive families. (Clearly this isn’t an everyday occurrence; nonetheless, it does happen, and it has been studied by behavioural geneticists.)
Each twin is brought up with adoptive siblings. Yet, despite sharing the same family environment throughout their childhood, when tested as adults, the twin and his or her adoptive siblings have very different levels of anxiety. There is, though, a significant correlation between the score of one twin and the other, despite the fact that they have never met, and between the scores of the twins and their birth parents. (Between the anxiety levels of the twins and their adoptive parents, there’s no correlation.) Twin adoption studies of this type provide persuasive evidence of genetic influence, but they’re difficult to run, not least because identical twins are relatively scarce.
In the case of anxiety, research indicates that genes certainly play a role. Everyone feels anxious from time to time; we’d hardly be human if we didn’t. But just how frequently, how intensely, and how lastingly we become anxious is part of our personality. Psychologists call this predisposition to anxiety ‘neuroticism’, and we all have a greater or lesser degree of it. Heritability for neuroticism has been put at around 40%. Anxiety disorders are moderately heritable – that’s to say, somewhere in the region of 20% to 40%. Research has also shown that some of the styles of thinking typical of people with anxiety problems – for example, the tendency to interpret ambiguous events as potentially dangerous or an acute sensitivity to the physiological changes triggered by anxiety – are also moderately heritable.
It’s important to be clear about the meaning of the term ‘heritability’. What it doesn’t mean is that 40% of a person’s level of neuroticism is necessarily the result of their genes. What it signifies is that around 40% of the differences in levels of neuroticism across the population are likely to be genetic in origin. So heritability tells us nothing about individual cases; it’s relevant only to broad statistical samples. The remainder of the differences between people are the product of environmental factors.
Our genes clearly play an important role in determining our level of anxiety. But which genes are involved? The short answer is that scientists don’t yet know. Several candidates have been suggested: variants in the glutamic decaroxylase 1 gene (GAD1), for example, have been associated with general emotional disorders, including anxiety problems. This is intriguing because GAD1 is involved in the production and transmission of gamma aminobutyric acid (GABA), which, as we saw in Chapter 2, helps calm us down when we’re anxious. If GAD1 isn’t functioning correctly, then neither will GABA, leading to exaggeratedly high levels of anxiety.
The best genetic research on anxiety looks for a gene that, like GAD1, could lead to a physiological hypersensitivity to potential danger. But, despite many exciting leads, no single ‘anxiety’ gene has been convincingly identified. To be meaningful, genetic studies require large numbers of people to be tested, huge amounts of research effort, and significant amounts of funding. Unsurprisingly, therefore, they are few and far between. And the findings from genetic studies are notoriously difficult to replicate: all too frequently, one research team will identify a plausible candidate gene only for subsequent studies to fail to find any link with anxiety.
Moreover, it seems unlikely that an experience as complex and varied as anxiety is the product of one or even a few isolated genes. Much more probable is the polygenic theory: that many different genes, each making a relatively small contribution, are involved in the generation and maintenance of anxiety. And so far the evidence suggests that what these genes are responsible for is a general tendency towards a high level of anxiety, or even general emotional arousal, rather than a specific anxiety disorder.
Identifying multiple genes involved in a complex interaction is clearly a tough assignment. But even if scientists are eventually successful, it may not be that those genes alone cause anxiety. Over the last decade or so, researchers have begun to see that there is a complex interaction of genes and environment. So, for example, although a person may be genetically susceptible to anxiety problems, they are by no means guaranteed to develop a disorder. That will happen only if the genetic vulnerability is triggered by particular life experiences. Equally, another person might experience the same events but, lacking the genetic vulnerability, will not go on to develop an anxiety disorder. As Avshalom Caspi and Terrie Moffitt have written:
the gene–environment interaction approach assumes that environmental pathogens cause disorder, and that genes influence susceptibility to pathogens.
Let’s look now at the ‘environmental pathogens’ involved in anxiety problems.
The environmental perspective
Important though genes are to the experience of anxiety, the environment makes an even more significant contribution. As we’ve seen, research indicates that genetic factors determine up to 40% of anxiety’s heritability – which means that the environment accounts for 60% or more. So what are the environmental risk factors for anxiety disorders?
We know relatively little about how experiences as an adult contribute to anxiety problems (though this kind of research has been done for depression and stress). The focus instead has been on childhood experiences, and four in particular:
• trauma and other upsetting events;
• parenting style;
• attachment style;
• learning from others.
But before we look at these four factors in more detail, we should point out that none is certain to cause anxiety disorders. For example, many peop
le endure a traumatic childhood without developing anxiety problems, and many of those who do suffer from an anxiety disorder have enjoyed a relatively happy upbringing. As we’ve seen in relation to genes, the process of causation is much more complex than a simple x = y. Indeed, it usually involves a complex interaction of genetic make-up and life experiences.
Trauma and other upsetting events
A plethora of research has shown that children exposed to traumatic or unpleasant experiences such as bullying or teasing, parental conflict, sexual or physical abuse, or the death of a parent are at greater risk of developing anxiety disorders.
For example, Murray Stein and colleagues surveyed 250 Canadian adults, half of whom had been diagnosed with an anxiety disorder and half (the control group) selected at random from the population of Winnipeg. They found that 15.5% of men and 33.3% of women with an anxiety disorder had suffered physical abuse as a child, compared to 8.1% of the control group. Similarly, childhood sexual abuse was much more common among women with anxiety disorders (45.1%) than women from the control group (15.4%).
Asking why these kinds of experiences result in anxiety problems might seem redundant. It’s hardly surprising that children who have been beaten or sexually abused may become unusually fearful. That said, as with all genetic or environmental contributors to anxiety, there’s nothing inevitable about this process. Many children suffer appalling trauma without developing anxiety disorders.
For those cases where anxiety disorders do result, psychologists have attempted to identify underlying patterns of thought and behaviour. It’s been suggested, for example, that children denied the care they need can form bleak opinions of themselves and other people. The world can seem a dangerous place, and they may lack faith in their ability to cope. From a different perspective, neurobiologists have pointed out that animals exposed to prolonged stress undergo permanent changes in their brain, making them especially susceptible to anxiety. Perhaps these early life experiences bring about a similar change in children?
Parenting style
Anxiety problems aren’t simply the legacy of abusive or neglectful parents. Parents who attempt to control their child’s behaviour too rigidly – quite possibly because of a desire to protect them – can unwittingly send out a signal that the world is a dangerous place. They also rob the child of the chance to discover that, by and large, she can cope with the problems she encounters. (This is reminiscent of the avoidance strategies discussed in the previous chapter.)
When anxious and non-anxious adults are asked by psychologists to recall their childhood, the anxious individuals are more likely to describe their parents as overprotective or controlling. Memories are not always reliable, of course. However, there is some observational research with children that backs up these findings. One study, for example, asked clinically anxious and non-anxious children to solve a number of difficult puzzles. The parents were told the solutions but advised only to get involved ‘if the child really needs it’. It soon became clear that parents of anxious children were much more likely to wade in than the other parents. Now if this tendency to control children’s behaviour shows up in such a relatively unthreatening context, how much more pronounced is it likely to be in situations where potential risk is greater?
But though this and other studies indicate an association between overprotective or controlling parenting and children’s anxiety, they don’t shed much light on the question of causation. Rather than producing anxiety in children, this kind of parenting might be a response to it. The kind of research that could answer this question – assessing parents and children over a number of years rather than at a particular moment – is quite rare. But what there is points to an interaction between a child’s temperament and an adult’s parenting style.
For instance, one study found that it was possible to predict a toddler’s level of fear by looking back to the frequency with which they had been held by their mother as a baby when they hadn’t needed help. But this was only true for those children who, as babies, had been very distressed when confronted with new people or situations. Hence a parent’s overprotectiveness may be a reaction to a child’s innate nervousness, but one that exacerbates that nervousness – which in turn triggers even more cautious and controlling behaviour on the part of the adult.
Attachment style
An alternative perspective on parent–child relationships, and their influence on anxiety, is provided by research on attachment style.
Young babies tend not to be very concerned about which person is providing the care and attention they require. As you may have noticed, they’re usually very happy to be passed from one adult to another, even if they have never met them before.
That all changes between the ages of seven and nine months. Gradually, the baby develops an attachment – defined by Jerome Kagan as ‘an intense emotional relationship that is specific to two people, that endures over time, and in which prolonged separation from the partner is accompanied by stress and sorrow’ – to one person in particular. Generally, this is the mother because she’s usually the prime carer, though it could be anyone who happens to be occupying that role. The baby cries when the mother leaves (this is known as separation anxiety), and clings to her when unfamiliar people are nearby (so-called stranger anxiety).
The immensely influential child psychiatrist John Bowlby (1907–90) argued that this desire for attachment is innate: we are genetically hard-wired to form these bonds because it represents our best chance of survival. Over subsequent months, the infant may develop attachments to many other figures in his/her life, but the bond with a primary caregiver – be it the mother, father, or someone else entirely – tends to remain the most significant. Bowlby believed that nothing is as important for a person’s future wellbeing as these early relationships.
It is possible to get a pretty reliable sense of a child’s attachment style by using the ‘Strange Situation’ technique devised in the 1960s by Mary Ainsworth (1913–99).
The Strange Situation begins with the researcher welcoming the baby – typically around twelve months old – and her mother to the room where the experiment is to take place. The researcher leaves and the baby is free to explore the exciting toys distributed throughout the room. A few minutes later, a stranger enters. The stranger is silent initially but after a minute or so begins chatting to the mother; the stranger then greets the child. The mother departs; three minutes later, she returns and the stranger exits. The mother leaves the baby on her own for a couple of minutes before the stranger reappears. Then the mother returns, the stranger departs, and the experiment is over.
What is crucial is the reaction of the baby to the mother’s absence and return. Securely attached children are happy to explore the room while their mother is present, but are moderately distressed when she leaves and delighted when she returns. Children with an anxious/resistant attachment style stick closely to their mother, no matter how alluring the toys scattered around the room, and are distraught when she leaves. Although the anxious/resistant child will run to her mother when she returns, she will then push the mother away, or even hit her. The anxious/avoidant child, on the other hand, tends to ignore her mother when she’s around and not be too concerned when she leaves. When the mother reappears, she’ll get the same aloof treatment as before.
In a remarkable study, psychologists interviewed 172 seventeen-year-olds, all of whom had undergone the Strange Situation assessment at twelve months of age. They discovered that the babies who had displayed an anxious/resistant attachment style were more likely to have developed subsequent anxiety problems.
Why is this? Anxious/resistant behaviour often reflects a child’s attempts to deal with inconsistent and unpredictable parenting, in which the kind of reception they receive depends entirely on the parent’s current mood. Possibly this kind of parenting instils a sense of insecurity into the child, making them fearful that no one may come to their aid if they run into trouble. As a result, the child is cons
tantly on the alert for danger. Perhaps too, there is a sense that the parent’s behaviour is a reflection of the child’s worthlessness, and by implication their inability to cope with challenges and dangers.
You may have noticed, incidentally, that anxious/avoidant children in this research were not at particular risk of later anxiety disorders. This kind of attachment is typically produced by parents who frequently ignore their child. Perhaps these children learn to manage the anxiety this kind of parenting can trigger by developing a protective independence. Unlike anxious/resistant children, who can sometimes find warmth and support from their parents, anxious/avoidant children realize that they have no choice but to look after themselves.
Learning from others
As we saw in Chapter 2, many of our fears are learned. And learned not simply from the events that happen to us directly, but from the people around us – either by what they explicitly tell us or by the way they behave. For most people, no one is more influential than their parents (though they can certainly learn from other important adults and from their peers).
A child’s instinctive ability to learn from their parents was demonstrated in an experiment carried out by the psychologists Friederike Gerull and Ronald Rapee. They showed 30 toddlers a green rubber snake and then a purple rubber spider, and studied their reactions. While the toys were on display, the children’s mothers were asked to react in a happy and encouraging way or in a frightened or disgusted manner.
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