may be stressful and lead to feelings of anxiety. this apprehension or fear of contact with outgroup members is often called interracial or intergroup anxiety. as is the case with the more generalized forms of social anxiety, intergroup anxiety has behavioral, cognitive, and affective effects. for instance, increases in schematic processing and simplified information processing can occur when anxiety is high. indeed, such is consistent with related work on attentional bias in implicit memory. additionally recent research has found that implicit racial evaluations (i.e. automatic prejudiced attitudes) can be amplified during intergroup interaction. negative experiences have been illustrated in producing not only negative expectations, but also avoidant, or antagonistic, behavior such as hostility. furthermore, when compared to anxiety levels and cognitive effort (e.g., impression management and self-presentation) in intragroup contexts, levels and depletion of resources may be exacerbated in the intergroup situation. trait anxiety can be either a short-term "state" or a long-term personality "trait." trait anxiety reflects a stable tendency across the lifespan of responding with acute, state anxiety in the anticipation of threatening situations (whether they are actually deemed threatening or not). a meta-analysis showed that a high level of neuroticism is a risk factor for development of anxiety symptoms and disorders. such anxiety may be conscious or unconscious. personality can also be a trait leading to anxiety and depression and their persistence. through experience, many find it difficult to collect themselves due to their own personal nature. choice or decision anxiety induced by the need to choose between similar options is increasingly being recognized as a problem for individuals and for organizations. in 2004, capgemini wrote: "today we're all faced with greater choice, more competition and less time to consider our options or seek out the right advice." in a decision context, unpredictability or uncertainty may trigger emotional responses in anxious individuals that systematically alter decision-making. there are primarily two forms of this anxiety type. the first form refers to a choice in which there are multiple potential outcomes with known or calculable probabilities. the second form refers to the uncertainty and ambiguity related to a decision context in which there are multiple possible outcomes with unknown probabilities. panic disorder main article: panic disorder panic disorder may share symptoms of stress and anxiety, but it is actually very different. panic disorder is an anxiety disorder that occurs without any triggers. according to the u.s. department of health and human services, this disorder can be distinguished by unexpected and repeated episodes of intense fear. someone with panic disorder will eventually develop constant fear of another attack and as this progresses it will begin to affect daily functioning and an individual's general quality of life. it is reported by the cleveland clinic that panic disorder affects 2 to 3 percent of adult americans and can begin around the time of the teenage and early adult years. some symptoms include: difficulty breathing, chest pain, dizziness, trembling or shaking, feeling faint, nausea, fear that you are losing control or are about to die. even though they have these symptoms during an attack, the main symptom is the persistent fear of having future panic attacks. anxiety disorders main article: anxiety disorder anxiety disorders are a group of mental disorders characterized by exaggerated feelings of anxiety and fear responses. anxiety is a worry about future events and fear is a reaction to current events. these feelings may cause physical symptoms, such as a fast heart rate and shakiness. there are a number of anxiety disorders: including generalized anxiety disorder, specific phobia, social anxiety disorder, separation anxiety disorder, agoraphobia, panic disorder, and selective mutism. the disorder differs by what results in the symptoms. people often have more than one anxiety disorder. anxiety disorders are caused by a complex combination of genetic and environmental factors. to be diagnosed, symptoms typically need to be present for at least six months, be more than would be expected for the situation, and decrease a person's ability to function in their daily lives. other problems that may result in similar symptoms include hyperthyroidism, heart disease, caffeine, alcohol, or cannabis use, and withdrawal from certain drugs, among others. without treatment, anxiety disorders tend to remain. treatment may include lifestyle changes, counselling, and medications. counselling is typically with a type of cognitive behavioural therapy. medications, such as antidepressants or beta blockers, may improve symptoms. about 12% of people are affected by an anxiety disorder in a given year and between 12–30% are affected at some point in their life. they occur about twice as often in women than they do in men, and generally begin before the age of 25. the most common are specific phobia which affects nearly 12% and social anxiety disorder which affects 10% at some point in their life. they affect those between the ages of 15 and 35 the most and become less common after the age of 55. rates appear to be higher in the united states and europe. short- and long-term anxiety anxiety can be either a short-term "state" or a long-term "trait." whereas trait anxiety represents worrying about future events, anxiety disorders are a group of mental disorders characterized by feelings of anxiety and fears. four ways to be anxious in his book anxious: the modern mind in the age of anxiety joseph ledoux examines four experiences of anxiety through a brain-based lens: in the presence of an existing or imminent external threat, you worry about the event and its implications for your physical and/or psychological well-being. when a threat signal occurs, it signifies either that danger is present or near in space and time or that it might be coming in the future. nonconscious threats processing by the brain activates defensive survival circuits, resulting in changes in information processing in the brain, controlled in part by increases in arousal and behavioral and physiological responses in the body that then produce signals that feed back to the brain and complement the physiological changes there, intensifying them and extending their duration. when you notice body sensations, you worry about what they might mean for your physical and/or psychological well-being. the trigger stimulus does not have to be an external stimulus but can be an internal one, as some people are particularly sensitive to body signals. thoughts and memories may lead to you to worry about your physical and/or psychological well-being. we do not need to be presence of an external or internal stimulus to be anxious. an episodic memory of a past trauma or of a panic attack in the past is sufficient to activate the defence circuits. thoughts and memories may result in existential dread, such as worry about leading a meaningful life or the eventuality of death. examples are contemplations of whether one's life has been meaningful, the inevitability of death, or the difficulty of making decisions that have a moral value. these do not necessarily activate defensive systems; they are more or less pure forms of cognitive anxiety. co-morbidity anxiety disorders often occur with other mental health disorders, particularly major depressive disorder, bipolar disorder, eating disorders, or certain personality disorders. it also commonly occurs with personality traits such as neuroticism. this observed co-occurrence is partly due to genetic and environmental influences shared between these traits and anxiety. it is common for those with obsessive–compulsive disorder to experience anxiety. anxiety is also commonly found in those who experience panic disorders, phobic anxiety disorders, severe stress, dissociative disorders, somatoform disorders, and some neurotic disorders. anxiety has also been linked to the experience of intrusive thoughts. studies have revealed that individuals who experience high levels of anxiety (also known as clinical anxiety) are highly vulnerable to the experience of intense intrusive thoughts or psychological disorders that are characterised by intrusive thoughts. risk factors a marble bust of the roman emperor decius from the capitoline museum. this portrait "conveys an impression of anxiety and weariness, as of a man shouldering heavy responsibilities". anxiety disorders are partly genetic, with twin studies suggesting 30-40% genetic influence on individual differences in anxiety. environmental factors are also important. twin studies show that individual-specific environments have a large influence on anxiety, whereas shared environmental influences (environments that affect twins in the same way) operate during childhood but decline through adolescence. specific measured 'environments' that have been associated with anxiety include child abuse, family history of mental health disorders, and poverty. anxiety is also associated with drug use, including alcohol, caffeine, and benzodiazepines (which are often prescribed to treat anxiety). neuroanatomy neural circuitry involving the amygdala (which regulates emotions like anxiety and fear, stimulating the hpa axis and sympathetic nervous system) and hippocampus (which is implicated in emotional memory along with the amygdala) is thought to underlie anxiety. people who have anxiety tend to show high activity in response to emotional stimuli in the amygdala. some writers believe that excessive anxiety can lead to an overpotentiation of the limbic system (which includes the amygdala and nucleus accumbens), giving increased future anxiety, but this does not appear to have been proven. research upon adolescents who as infants had been highly apprehensive, vigilant, and fearful finds that their nucleus accumbens is more sensitive than that in other people when deciding to make an action that determined whether they received a reward. this suggests a link between circuits responsible for fear and also reward in anxious people. as researchers note, "a sense of 'responsibility', or self-agency, in a context of uncertainty (probabilistic outcomes) drives the neural system underlying appetitive motivation (i.e., nucleus accumbens) more strongly in temperamentally inhibited than noninhibited adolescents". the gut-brain axis the microbes of the gut can connect with the brain to affect anxiety. there are various pathways along which this communication can take place. one is through the major neurotransmitters. the gut microbes such as bifidobacterium and bacillus produce the neurotransmitters gaba and dopamine, respectively. the neurotransmitters signal to the nervous system of the gastrointestinal tract, and those signals will be carried to the brain through the vagus nerve or the spinal system. this is demonstrated by the fact that altering the microbiome has shown anxiety- and depression-reducing effects in mice, but not in subjects without vagus nerves. another key pathway is the hpa axis, as mentioned above. the microbes can control the levels of cytokines in the body, and altering cytokine levels creates direct effects on areas of the brain such as the hypothalamus, the area that triggers hpa axis activity. the hpa axis regulates production of cortisol, a hormone that takes part in the body's stress response. when hpa activity spikes, cortisol levels increase, processing and reducing anxiety in stressful situations. these pathways, as well as the specific effects of individual taxa of microbes, are not yet completely clear, but the communication between the gut microbiome and the brain is undeniable, as is the ability of these pathways to alter anxiety levels. with this communication comes the potential to treat anxiety. prebiotics and probiotics have been shown to reduce anxiety. for example, experiments in which mice were given fructo- and galacto-oligosaccharide prebiotics and lactobacillus probiotics have both demonstrated a capability to reduce anxiety. in humans, results are not as concrete, but promising. genetics genetics and family history (e.g. parental anxiety) may put an individual at increased risk of an anxiety disorder, but generally external stimuli will trigger its onset or exacerbation. estimates of genetic influence on anxiety, based on studies of twins, range from 25 to 40% depending on the specific type and age-group under study. for example, genetic differences account for about 43% of variance in panic disorder and 28% in generalized anxiety disorder. longitudinal twin studies have shown the moderate stability of anxiety from childhood through to adulthood is mainly influenced by stability in genetic influence. when investigating how anxiety is passed on from parents to children, it is important to account for sharing of genes as well as environments, for example using the intergenerational children-of-twins design. many studies in the past used a candidate gene approach to test whether single genes were associated with anxiety. these investigations were based on hypotheses about how certain known genes influence neurotransmitters (such as serotonin and norepinephrine) and hormones (such as cortisol) that are implicated in anxiety. none of these findings are well replicated, with the possible exception of tmem132d, comt and mao-a. the epigenetic signature of