Anxiety Disorders

Anxiety disorders are those conditions in which the individual experiences excessive, continual or prolonged anxiety for no obvious reason or where the anxiety is significantly disproportionate to the cause. Extreme anxiety can result in intense apprehension or panic
1. Generalised Anxiety. Generalized anxiety disorder is a common chronic disorder characterized by continual or prolonged anxiety that is not focused on any one object or situation. Those suffering from generalized anxiety experience non-specific persistent fear and worry and become excessively concerned with everyday matters. Additional symptoms include the following.

• Restlessness or feeling keyed-up or on edge
• Being easily fatigued
• Difficulty concentrating or mind going blank
• Irritability
• Muscle tension
• Sleep disturbance

A diagnosis of Generalised Anxiety should be considered if the patient has the general symptoms plus at least three of the additional symptoms. Generalized anxiety disorder may have its onset in early childhood or be triggered by a significant stressful situation. It is the most common anxiety disorder to affect older adults.
2. Panic Disorder. This is characterised by the sudden onset of episodes of intense fear or apprehension. These feelings reach a maximum within ten minutes, may be brief, or may last for several hours. The attacks may be triggered by stress or surroundings; however there is often no obvious explanation. Fear itself may trigger these attacks; however the response is completely disproportionate to the cause of fear.
At least four of the following additional symptoms should be present for a diagnosis of Panic Disorder.

• Palpitations (pounding, racing or irregular heart beat)
• Sweating
• Trembling or shaking
• Dyspnoea (shortness of breath)
• Sensation of choking
• Chest pain or discomfort
• Nausea or abdominal distress
• Feeling dizzy, unsteady, lightheaded, or faint
• Derealisation or depersonalization (a feeling that you or your surroundings are unreal)
• Fear of losing control or going crazy
• Fear of dying
• Paresthesias (numbness, tingling)
• Chills or hot flashes

These two conditions may overlap with patients who have anxiety disorder being susceptible to occasional panic attacks.

Some of the parts of the brain involved in response to fear or anxiety

Anxiety or fear has a well documented physiological effect on the brain, the endocrine (hormone) system and the autonomic (involuntary) nervous system. An area of the brain known as the locus coeruleus responds to stimuli from the senses. In a relaxed state the neurons in the locus coeruleus will produce normal levels of a neurotransmitter called norepinephrine. If the senses perceive danger the neurons will produce more norepinephrine in proportion to the perceived threat. Rising levels of norepinephrine increase awareness, information processing and motivation in the prefrontal cortex and nucleus accumben by increasing the activity of neurons in these areas of the brain. They also activate the hypothalamus and, pituitary glands which stimulate the adrenal glands to produce more cortisol.
Norepinephrine also acts directly on part of the autonomic nervous system called the sympathetic system. This exerts automatic control over a variety of bodily functions including heart rate, gut motility, urine output, pupil diameter and sweating.
Significantly increased levels of hormones and neurotransmitters, particularly norepinephrine, epinephrine and cortisol can result in dramatic physiological changes, including:

• Acceleration of heart and lung action
• Paling or flushing, or alternating between both
• Inhibition of stomach and upper-intestinal action (digestion slows down or stops)
• General effect on the sphincters of the body
• Constriction of blood vessels in many parts of the body
• Liberation of nutrients (particularly fat and glucose) for muscular action
• Dilation of muscle blood vessels and muscle tension
• Inhibition of the lachrymal gland (responsible for tear production) and salivation
• Dilation of pupil (mydriasis)
• Relaxation of bladder
• Evacuation of colon
• Inhibition of erection
• Auditory exclusion (loss of hearing)
• Tunnel vision (loss of peripheral vision)
• Acceleration of instantaneous reflexes
• Shaking
• Sweating in anticipation of increased body heat due to increased muscle activity

This is known as the “fight or flight” or stress response and prepares the body for a rapid and effective response to perceived threats. Most of the physiological changes are designed to shut down any unnecessary activities increase blood flow and energy supply to muscles, and maximise alertness and visual focus. The physiological response may be mild or dramatic depending on the degree of perceived threat. The levels of the various neurotransmitters and hormones that trigger this response are normally controlled by a feedback mechanism that switches off the response at certain levels or when the threat has been removed, neutralised or reassessed. One of the main control mechanisms in this feedback process is thought to be binding of gamma-aminobutyric acid (GABA) to receptors on neurons in the brain, which stops the neuron firing.  Failure of this mechanism can result in excessive or prolonged firing of neurons and an uncontrolled physiological response.
Low or moderate levels of anxiety or fear may trigger some of the above physiological changes at low or moderate levels. High levels of anxiety or fear may trigger most of these physiological changes at dramatic levels.
Generalised anxiety disorder is thought to be due to repeated triggering of the stress response, and/or a failure to switch off the response at an appropriate level.  This may be due to continual exposure to situations which generate fear or stress or exposure to relatively normal situations which the patient has learned to fear. . In some cases the trigger may be difficult to identify.
 Alternatively, it may be due to exposure to normal levels of fear or stress in an individual with a defective feedback control mechanism.
The stress response may become a panic attack if the stress response is excessive or if the feedback control mechanism fails to function at the appropriate level.
Repeated or constant triggering of the stress response can result in excessive fatigue, high blood pressure, digestive disorders, anorexia, repeated infections and erectile dysfunction. These disorders may further increase anxiety generating a vicious circle of deteriorating physical and mental health.
In many cases, anxiety is associated with depression. This may be the body's attempt to limit damage from over activation of the stress response by shutting down all unnecessary activity.
Anxiety disorders can be triggered by substance abuse, medications, herbal remedies and other toxic substances. These types of anxiety disorders are often misdiagnosed or under-diagnosed.
A substance-induced anxiety disorder may be caused by alcohol, amphetamines (and related substances), caffeine, cannabis (marijuana), cocaine, hallucinogens, inhalants and phencyclidine (PCP) or related substances.
Anxiety symptoms can also result from withdrawal from alcohol, sedatives, hypnotics, and anxiolytics or cocaine.
Some of the medications which may induce anxiety symptoms include anaesthetics and analgesics, sympathomimetics (epinephrine or norepinephrine, for example) or other bronchodilators, anticholinergic agents, anticonvulsants, antihistamines, insulin, thyroid preparations, oral contraceptives, antihypertensive and cardiovascular medications, antiparkinsonian medications, corticosteroids, antidepressant medications, lithium carbonate, and antipsychotic medications.
Heavy metals and toxins, such as volatile substances like fuel and paint, organophosphate insecticides, nerve gases, carbon monoxide, and carbon dioxide may also induce anxiety.