Generalised anxiety disorder (GAD) is one of several anxiety disorders listed in the American Psychiatric Association’s 1994 Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR).
The central symptom that characterises GAD is worry, defined as the cognitive tendency to focus on a problem that one is unable to let go of. Although everyone worries about events in their lives from time to time, the DSM-IV-TR stipulates that the worries of those with generalised anxiety disorder (GAD) are excessive, uncontrollable, long lasting and impairs their day to day functioning.
Other symptoms of anxiety include tiring easily, restlessness, difficulty concentrating, irritability and muscle tension. Symptoms must be present for at least six months in order for an individual to receive a diagnosis of generalised anxiety disorder (GAD).
Comorbidity of Anxiety Disorders
Generalised anxiety disorder (GAD) is often chronic and typically thought to begin in adolescence. However, many sufferers report having had a tendency to worry excessively all their lives. Generalised anxiety disorder (GAD) is frequently comorbid with other anxiety disorders.
Brown and colleagues reported that over half of sufferers will have received a diagnosis of another anxiety disorder. This is thought to be due to two primary reasons. Firstly, many of the symptoms that characterise the different anxiety disorders overlap, and secondly, factors that are thought to contribute to the development of an anxiety disorder may increase the risk to all anxiety disorders.
Furthermore, anxiety disorders are often comorbid with other disorders such as substance abuse disorders, personality disorders and depression. Depression often develops after the onset of an anxiety disorder and is thought to be a result of the feelings of hopelessness and despair produced by anxiety.
Genetic and Neurobiological Factors Related to Anxiety Disorders
Psychologists have identified a number of factors that may increase an individual’s risk of developing an anxiety disorder, such as generalised anxiety disorder (GAD). Twin studies have suggested that genetic factors may play a role in the development of anxiety disorders, with generalised anxiety disorder (GAD) thought to have a heritability of 20-40%.
It is also thought that there may be a neurobiological basis of anxiety disorders. The fear circuit, a set of brain structures that tend to be activated when a person feels anxious or fearful, has been found to show elevated activation in those with anxiety disorders, particularly in regards to the amygdala.
Furthermore, abnormal functioning of the neurotransmitters in the fear circuit has been found in those with anxiety disorders, such as poor functioning of the serotonin system and abnormally high levels of norepinephrine.
Personality and Cognitive Factors Related to Anxiety Disorders
Personality traits that may contribute to the development of an anxiety disorder have also been identified. Some infants show a trait known as behavioural inhibition, which is characterised by agitation and crying when faced with novel stimuli.
A study by Kagan & Snidman in 1999 found that 45% of infants who exhibited signs of behavioural inhibition had begun to show signs of anxiety at age seven. The trait neuroticism has also been associated with anxiety disorders. It has been found that those with high levels of neuroticism are twice as likely to develop an anxiety disorder, and that neuroticism scores are a predictor of the onset of anxiety disorders and depression.
Those with anxiety disorders also show different cognitive behaviours in comparison to those without anxiety disorders. Those who have received a diagnosis of an anxiety disorder have been found to show selective attention to signs of threat. This is thought to happen automatically and very quickly, perhaps before the individual is consciously aware of the stimulus in question.
Lastly, as with depression, negative life events have often been found to precede the onset of anxiety. In 1989, Finlay-Jones estimated that 70% of people with an anxiety disorder had reported a negative life event before receiving a diagnosis of an anxiety disorder.