Anxiety is a common problem, typically beginning early in life. This article explores reasons for individual differences in levels of anxiety among children, by reviewing the genetic literature. The plethora of research to date has demonstrated clearly that both genes and environmental influences play important roles in explaining differences in levels of anxiety of various types among children. This has encouraged researchers to search for specific genes and environmental influences upon anxiety. Despite important progress in identifying links between anxiety and specific genes-including associations between serotonin and dopamine genes and different symptoms of anxiety-overall, progress has been slow because multiple genes of small effect size are likely to influence anxiety. This article explains how the hunt for genes involved in anxiety is likely to benefit from genetically sensitive research, which examines the co-occurrence of symptoms; includes measures of the environment; and examines endophenotypes and risk pathways.
KEY WORDS: anxiety; children; environment; genes; twins
IntroductionAnxiety is characterized by fear, concern or dread. This may be related to a specific event or situation that is perceived threatening, or may be more pervasive. Individuals with high levels of anxiety may meet criteria for an anxiety disorder, of which there are many types (Diagnostic and Statistical Manual of Mental Disorders-IV, American Psychiatric Association, 1994). Although anxiety is a common difficulty occurring throughout the life-course it typically begins early in life Kessler, Berglund, Demler, Jin, & Walters, 2005), which suggests that research examining the origins of anxiety may be beneficial in childhood. While most children show at least some symptoms of anxiety, the exact prevalence of anxiety disorders is debatable. For example, a review of epidemiological studies examining rates of anxiety disorders in preadolescent children reported prevalence rates between 2.6 and 41.2% (Cartwright-Hatton, McNicol, & Doubleday, 2006).Given the widespread nature of childhood anxiety, researchers are trying to understand more about why anxiety develops and persists. One research area of rapid growth in this respect is genetics and this type of research has tended to focus upon symptoms of anxiety within the full range as opposed to anxiety disorders. A sceptic may point out that we are stuck with the genes that we are born with and argue that therefore, understanding the way in which genes influence behavior is of little use. However, as will be discussed in the course of this article, it is becoming increasingly clear that although it is true that our genes do not change throughout development, genes may become more or less influential over time; and the environment can influence the way in which our genes impact upon our emotions and behaviors. This article will document the progress that has been made in understanding genetic and environmental influences on childhood anxiety. Although there are numerous reviews of ...