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Anxiety Disorder, Specific Phobia

Author: Sandra L Friedman, MD, MPH, Assistant Professor of Pediatrics, Harvard University Medical School; Director of Pediatrics, LEND/UCEDD, Department of Medicine, Division of General Pediatrics, Children's Hospital of Boston
Coauthor(s): Kerim M Munir, MD, MPH, DSc, Director of Psychiatry, LEND/UCEDD, Division of General Pediatrics, Dir of Mental Health and Developmental Disabilities (MHDD) Training Prog, Children's Hospital Boston; Marilyn T Erickson, PhD, Professor Emeritus, Department of Psychology, Virginia Commonwealth University
Contributor Information and Disclosures

Updated: Dec 5, 2008

Introduction

Background

Phobias are the most common anxiety disorder. Specific phobia (SP) is characterized by extreme and persistent fear of specific objects or situations that present little or no real threat. Specific phobia has behavioral, cognitive, and physiologic manifestations.

A summary of the diagnostic criteria for specific phobia, based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, includes the following:¹

• Criterion A: The patient has persistent or irrational fear that is unreasonable or excessive and is triggered by the presence or anticipation of a specific object or situation.
• Criterion B: Exposure to the above noted event or object almost always results in an immediate anxiety response.
• Criterion C: The person acknowledges this response to be unreasonable or excessive.
• Criterion D: The person either avoids such situations or objects or else experiences exposure with intensive anxiety or distress.
• Criterion E: The avoidance or distressful response significantly interferes with a person's daily functioning.
• Criterion F: Duration is at least 6 months for individuals younger than 18 years.
• Criterion G: The anxiety, distressful response, or avoidance is not accounted for by other mental disorders (see Differentials).

The patient must have one of the following 5 subtypes that best describe phobias:

• Animal
• Natural environment
• Blood-injection injury
• Situational
• Other (must be distinguished from normal fear and anxiety)

Individuals may have more than one specific phobia, as clustering often occurs. Animal, natural environment, and situational specific phobias tend to cluster; 70% of those with blood specific phobia also have injection specific phobia.

Specific phobia may be associated with problems with peers, family, and school. These problems may negatively affect self-esteem. Unlike adults, children may not acknowledge their fear is excessive or unreasonable.

Fears and phobias are common in young children; thus, preschool children are rarely referred and diagnosed as phobic. Common fears of childhood need to be distinguished from specific phobia, as the latter is irrational, interferes more with daily routines, and leads to maladaptive behaviors. In some instances, natural environmental contingencies may extinguish a fear, whereas, in other instances, a fear may remain for the person's entire life. Specific phobias in children generally attenuate over time, although they may persist into adulthood. In contrast, specific phobias that appear in adolescents and adults tend to persist, with only approximately 20% resolving without intervention.

Assessments generally consist of structured or semistructured interviews by the practitioner with the child and his or her parents. Various rating scales are also available to assess anxiety disorders.

Pathophysiology

The specific nature of anxiety associated with specific phobia is felt to be associated increase in tonic cardiac vagal tone, manifested by an increase in heart rate, which is considered to be greater compared with other anxiety disorders. These responses are mediated by the autonomic nerve system, more specifically by its parasympathetic branch. The vagus nerve attenuates the sympathetic nervous system output and is key to responsiveness to environmental cues.

Children with specific phobias are felt to display a greater degree of response to perceived threats, although they do not demonstrate an increase in anticipatory responsiveness. However, this physiologic change is not the same with all specific phobias because different specific phobias have been associated with differences in cardiac vagal tone. Functional MRI (fMRI) findings have suggested a neural network for the processing of threatening stimuli, with increased activation in the prefrontal cortex, insula, and posterior cingulated cortex, when subjects were exposed to phobia-sensitive words (eg, spider phobia) compared with subjects without phobias.

Frequency

United States

The National Institute of Mental Health (NIMH) estimates that 5-12% of Americans have phobias; specific phobias affect approximately 6 million Americans.² Approximately 7-9% of children have been estimated to have specific phobia. No significant differences have been noted between whites and persons of Hispanic or African descent. No conclusive evidence links socioeconomic status with specific phobia.

International

The prevalence rates and types of phobias vary among various cultural and ethnic groups. The overall reported prevalence rates in children in New Zealand, Puerto Rico, Switzerland, and Germany are low.

Sex

Females may be at higher risk for developing specific phobia than males. The sex difference is less notable for certain specific phobias, such as heights.

Age

The mean age of onset depends on the type of phobia. Animal, blood, and storms and water specific phobias typically develop in early childhood. Height specific phobia develops in teenagers. Situational specific phobias (eg, claustrophobia) typically develop during the late teenage years and early third decade of life.

Fears and phobias are common in young children. Referral rates tend to increase in mid-to-late childhood and early adolescence. The peak age for referral of children diagnosed with specific phobia is 10-13 years, with the average age of onset of symptoms at approximately 8 years.

Clinical

History

Behaviorally, phobias manifest as the need to escape or avoid the feared object or situation. The fear may be expressed somatically by tremor, feeling faint or actually fainting, nausea, diaphoresis, rapid heart rate, increased blood pressure, and feelings of panic. Children may present with crying, tantrums, clinging, or immobilization.

Parents of children with anxiety disorders typically have a higher than average incidence of anxiety disorders in their histories. Similarly, children whose parents have a specific phobia (SP) display a higher rate of specific phobia than control subjects.

Causes

Numerous theories about the etiology of specific phobias have been offered, with psychoanalytic theory offering early explanation, although it is no longer ascribed. Many other theories have been proposed, citing learning theories, environmental influences, and genetic factors, as well as a combination of these factors. However, genetic and environmental factors are generally acknowledged to influence behavior, including anxiety disorders in general and specific phobias in particular.  

• Learning theories
  • Classic conditioning: A previous neutral stimulus has been paired with an aversive stimulus that elicits a strong fear or emotional response. Often, adults in the child's life may be unaware of the aversive episode. Some believe this learning may be direct or vicarious, which entails witnessing an event involving another person that elicits fear.
  • Operant conditioning: Parents may inadvertently reinforce the phobic behavior by providing the child with increased amounts of social attention surrounding the avoidant behavior. In young children, familial influences have been reported to affect comorbidity between specific phobia and separation anxiety and between specific phobia and social phobia. These influences are felt to reflect shared environmental influences more than genetic factors. Learning and modeling, as well as parent-child interactions, have been proposed as possible explanations.
• Cognitive models: Because learning theories are not felt to adequately explain the development and persistence of phobias, attention has been focused on the role of cognition. Children with anxiety disorders are more likely to display distorted and maladaptive thoughts, although the extent to which these negative thoughts are causes or consequences of their fears is unclear.
• Genetic, familial, and constitutional theories
  • A familial component of specific phobia is often observed, although the type of specific phobia is usually different.
  • Genetic factors are felt to contribute to specific phobia. Genetic effects on early onset disorders have been reported to be more substantial than environmental factors.
  • Constitutional factors and individual experiences increase the risk for developing anxiety disorders.
  • Children with anxiety disorders are more likely to display distorted and maladaptive thoughts, but whether these negative thoughts are causes or consequences of their fears is unclear.
  • Manifestations of constitutional factors may be apparent in individual differences in responsiveness to environmental events. A sudden loud sound elicits a range of emotional responses in different children, some of which are the result of biological differences.
  • Children who demonstrate a stable behavioral inhibition (becoming excessively distressed and withdrawn in novel situations) from infancy through childhood have higher rates of anxiety disorders than children who are not consistently inhibited. These findings suggest that childhood behavioral inhibition may be a risk factor for developing anxiety disorders.
  • Personality is felt to be heritable.
  • Increased fears and phobias have been identified in children of parents with major depressive disorder and anxiety, although not found to be associated with parents with major depressive disorder without anxiety.³
  • Avoidance of new foods has been found to be highly heritable in children aged 8-11 years, although less than one fourth of children with this presentation are also believed to be influenced by nonshared environmental factors.⁴

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