Anxiety: An Overview
Appropriate levels of anxiety, commonly referred to as
fear or worry, is a normal mental process that has remained with humans through
evolution because its presence has protective and life surviving traits. Fear
and anxiety create a behavioral response that prevents an individual from entering
situations that are likely to cause injury, pain and possibly death. Anxiety is
peaked when there is a feeling on impending danger and perceptions stimulant
the brain to be on high alert and prepare for the “fight or flight” response.
The uncomfortable feeling of anxiety prevents an
individual from entering environments that may be dangerous to our well-being,
such as steep rocky cliffs or “bad” neighborhoods. However, some have
neurological settings that trigger anxiety at low levels of danger. Less
dangerous environments, or simply even thoughts, in these individuals can
prematurely generate anxiety that interferes with ones life. For example, if
someone has an excessive fear of heights, they may not seek employment or
attend a school that requires them to be on higher floors. The evolutionary
fear of heights was important so early humans would not pursue prey or food in
elevated levels where there was a significant risk of falling, injury or death.
Anxiety has an important role in the maintenance for our well-being, but
excessive anxiety can significantly impair an individual’s life.
It is often difficult to determine the precise difference
between appropriate levels of anxiety and those that are pathological.
Essentially, a level of fear or anxiety are considered abnormal if persistent,
intense and without real danger present. When the intensity and duration of the
presence of fear and anxiety is disproportional, or is not even associated with
a genuine risk, this results in a debilitating state of prolonged anxiety.
Individuals experiencing pathological anxiety display signs of excessive
worrying, restlessness, fatigue, irritability, muscle tension, along with
concentration and sleep disturbances. Physical symptoms include tachycardia, high
blood pressure, sweating, dry mouth and dilated pupils.
Anxiety disorders are a group of mental health conditions
that include: generalized anxiety disorder (GAD), social anxiety,
post-traumatic stress disorder (PTSD) and panic disorder.[1]
A diagnosis of anxiety disorder is warranted when the extent of the anxiety
interferes with thought processes and behavior that prevents an individual from
performing daily activities and maintaining relationships. The two most
predictive indicators to determine if the level of anxiety is greater than normal
is; 1) determining the percent of the day in worry, and 2) the number of areas
one worries about.[2]
Any one of the anxiety conditions can lead to reduced life experiences and
impair ones ability to function in society.
Anxiety is generated and propagated in specific neural
circuits in the brain, which subsequently activates several organ systems in
the body to prepare the body for something harmful to happen. When anticipating
physical danger, the brain prepares the body to fight to survive, or if the
stimulus too great (a bear), to prepare to run to safety (flight). In
preparation for these physical events, neuroendocrine signals stimulate the
heart to increase the rate and amount of oxygenated blood pumped to muscles, increases
the release of epinephrine (adrenaline) to the sympathetic nervous system and
steroids from adrenal glands, and increases perspiration to cool the body.[3]
This manuscript will use the term anxiety to represent
any level of excessive fear, stress or anxiety that causes mental anguish and
limits ones ability to enjoy and freely participate in their lives.
Epidemiology
Anxiety disorders are most common of mental health
conditions. A systematic meta-analysis, which included 87 studies from 44
countries, reported that the average incidence of anxiety disorders was 15%.[4]
In the U.S., a 2010 prospective study found the lifetime prevalence of GAD was
14.2%. [5]
An Australian study in 2014, found that the lifetime prevalence of anxiety
disorders occurred in 20% of the population with an average age of symptom
onset at 19 years. The most common risk factors for developing an anxiety
disorder are: female, single, unemployed, having a physical health condition
and a family history of mental health disorders. [6]
This reported incidence of anxiety disorders does not
include individuals with mild to moderately elevated anxiety levels, referred
to as trait anxiety. This group does not meet the criteria for an anxiety
disorder, but their lives are detrimentally affected by excessive anxiety. The incidence of trait anxiety is believed to
be significantly growing in today’s global, high-tech, fast paced societies.
The understanding of the neurochemical etiology of
anxiety has evolved tremendously over the past two decades. Serotonin, g-aminobutyric
acid (GABA), glutamate and norepinephrine neurotransmitter activity and
specific receptors in key areas of the brain have received the greatest amount
of research. Clinical, biochemical, radiological and molecular imaging studies
have consistently documented the important role neurotransmitters play in the
modulation of mood and anxiety.
Risk Factors
Risk factors for developing excessive anxiety are a
combination of environmental, social, neurological, medical and genetic factors.
Poor living conditions, abuse, bereavement, divorce/separation, depression,
comorbid medical or neurological disorders and family history of anxiety are
the most commonly associated risk factors.[7]
[8]
[9]
[10]
Recent research indicates that neurotransmitter activity changes are key
components in generating the emotional symptoms and physical consequences of
anxiety.
Those with neurological conditions are at increased risk
for developing an anxiety disorder. The impaired function responsible for a
given neurological disorder may influence the modulation of anxiety related
neural circuits. The most common neurological disorders associated with a high
rate of co-morbid anxiety are epilepsy and multiple sclerosis.[11]
Associated Disorders
There is a significant literature confirming that
anxiety, and even anxiety trait, impair cognitive functions. These functions
include reduced goal-directed sustained attention,[12]
prefrontal brain attention control [13]
and ability to inhibit or block out distractions. [14]
Anxiety and high levels of perceived stress have been
shown to disrupt the body’s immune function [15]
[16]
by reducing the actual number of white blood cells (WBC) and the cytokines that
provide the signals for specific infections. [17]
These factors can lead to suppress the immune system and increase the risk of
infections.
Anxiety increases the risk of developing several physical
and mental conditions and diseases. GAD was found to be highly associated with
cardiovascular deaths in recent studies.[18]
[19]
[20]
Over a 20-year monitoring study, it was determined that negative health
outcomes were proportionately related to the degree of persistent anxiety.[21]
In addition, anxiety is comorbid and often complicates survival in many
conditions such as cardiovascular disease, depression, Parkinson’s, multiple
sclerosis, epilepsy and schizophrenia. [22]
[23]
[24]
[25]
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