Generalised anxiety disorder
At least 6 months of excessive worry about everyday issues that is disproportionate to any inherent risk, causing distress, or impairment.
The worry is not confined to features of another mental disorder, or as a result of substance abuse or a general medical condition.
At least 3 of the following emotional, somatic, and cognitive symptoms are present most of the time:
restlessness or nervousness
being easily fatigued
Other common complaints are autonomic in nature, such as sweating, lightheadedness, palpitations, dizziness, and epigastric discomfort. 
Anxiety may be 'free-floating' (i.e., not restricted to, or even strongly predominating in, any particular environmental circumstances). 
Examples of worries include fears that the patient or a relative will shortly become ill or have an accident.
FHx of anxiety
Physical or emotional stress
Hx of physical or emotional trauma
Other anxiety disorder
Characterised by recurrent episodes of sudden onset of anxiety
Strong autonomic and physical complaints without the predominant picture of worry. 
At least 4 symptoms including shortness of breath, palpitations, shakiness, nausea, hot or cold flushes, dizziness, and fear of dying.
Panic may exist along with GAD
Anxiety or persistent fear is limited to social situations and fear of social scrutiny or embarrassment. 
Anxiety is directly related to compulsions or obsessions.
Anxiety is directly related to exposure to reminders of past trauma.
Anxiety is directly related to specific physical complaints.
Thorough medical evaluation shows no basis for physical complaints.
Anxiety is directly related to exposure to:
substance (e.g., caffeine, toxin, alcohol, illicit drug)
drug (e.g., salbutamol, theophylline, corticosteroid, antidepressant)
herbal medicine (e.g., ma huang, St. John's wort, ginseng, guarana, belladonna).
Anxiety may occur during withdrawal of a substance (e.g., alcohol, opioids, sedative-hypnotics)
Characteristic symptoms such as shakiness (i.e., rapid heart rate, fluctuating blood pressure), and, if delirium is present, mental confusion.
Typical signs on are tachypnoea, tachycardia, and disorientation
Anxiety is directly related to a fear of gaining weight.
Body weight <85% of ideal.
Situational anxiety (non-pathological)
Anxiety can be avoided and is more controllable and less pervasive.
Situational worries are less likely to be accompanied by physical symptoms. 
Restlessness, fatigue, and other physical symptoms are rarely present.
Anxiety occurs temporarily in response to a life stressor and does not persist for more than 6 months after the stressor ends.
Anxiety symptoms are predominantly cardiac in nature
Palpitations, sensation of rapid heartbeat or skipped heartbeat, dizziness, dyspnoea on exertion, chest pain, and numbness
Chest pain is typically exertional.
Weight loss, warm moist skin, heat intolerance, ophthalmopathy, or goitre.
TFTs (increased T4, decreased TSH) can identify primary hyperthyroidism or use of excessive thyroid hormone.
Anxiety limited to the time period of the infection.
Typically, burning epigastric pain which occurs hours after meals or with hunger, relieved by food or antacids.
Chronic diarrhoea, weight loss, and right lower quadrant abdominal pain mimicking acute appendicitis.
Perianal lesions including skin tags, fistulae, abscesses, scarring or sinuses.
Alteration of bowel habits associated with pain, and abdominal discomfort, bloating, or distention.
One study in Europe showed that 76% of people who had more than 1 mental disorder for 12 months had GAD.
In the US, GAD has an estimated lifetime prevalence of 5% and a 12-month prevalence of 3%
About two thirds of patients diagnosed are female, and more women (55% to 60%) than men are diagnosed in clinical settings. 
Over half of the people seeking help have an onset in childhood or adolescence.
A large US epidemiological study found that almost half of people retained the diagnosis over 2 years after diagnosis. 
No single aetiology exists
A systematic review found that bullying or peer victimisation among youths was associated with an increased incidence. 
A review of 35 twin and family studies found a significant association with other anxiety disorders and depression, suggesting a common underlying genetic factor. 
Abnormality of chromosome 15 has been associated with panic, agoraphobia, social phobia, and joint laxity in families, and with panic disorder in non-familial cases.
However, this data is preliminary only
Further investigations, including more sophisticated studies of genetic markers, are warranted to substantiate this and identify other genetic factors associated with anxiety disorders. 
Presence of risk factors
Excessive worry for at least 6 months
Anxiety not confined to another mental disorder
Anxiety not due to medication or substance
Increased heart rate
Shortness of breath
Exaggerated startle response
Not clearly understood
Studies have identified changes in cerebral blood flow in response to stress
Hypervigilance and increased metabolic activity suggest hyperactive brain circuitry. 
Multiple neurotransmitters involving wide areas of the brain have been implicated in anxiety and other disorders 
Including receptors for benzodiazepines, N-methyl-D-aspartate/glutamate, serotonin, and cholecystokinin.
Abnormalities in brain corticotrophin-releasing factor secretion in the hypothalamic-pituitary-adrenal axis appear to co-occur with anxiety episodes
May adversely affect neurotransmitters and arousal. 
The associated heightened vigilance and arousal are associated with insomnia and diurnal fatigue. 
DSM-IV-TR criteria for GAD:
The worry is not confined to features of another mental disorder or as a result of substance abuse or a general medical condition.
At least 3 of the following symptoms are present most of the time:
restlessness or nervousness, being easily fatigued, poor concentration, irritability, muscle tension, or sleep disturbance. 
Tests to rule out other conditions:
Antidepressants if depression coexists
SSRIs, SNRIs, or buspirone are considered the drugs of choice
Pharmacotherapy should be given for at least 6 to 8 weeks to determine efficacy, and continued for up to 6 to 12 months if effective. 
The physician may attempt to taper the medication after this period, monitoring the patient for recurrence of symptoms.
With proper treatment, a decrease in symptoms, improved psychosocial functioning, and a reduction in over-utilisation of medical care can be achieved.
Generalised anxiety disorder may recur under physical or emotional stress.