Generalized anxiety disorder (GAD) is a common disorder, characterized by long-lasting anxiety that is not focused on any one object or situation. Those suffering from generalized anxiety disorder experience non-specific persistent fear and worry, and become overly concerned with everyday matters. Generalized anxiety disorder is "characterized by chronic excessive worry accompanied by three or more of the following symptoms: restlessness, fatigue, concentration problems, irritability, muscle tension, and sleep disturbance". Generalized anxiety disorder is the most common anxiety disorder to affect older adults. Anxiety can be a symptom of a medical or substance abuse problem, and medical professionals must be aware of this. A diagnosis of GAD is made when a person has been excessively worried about an everyday problem for six months or more. A person may find that they have problems making daily decisions and remembering commitments as a result of lack of concentration/preoccupation with worry. Appearance looks strained, with increased sweating from the hands, feet, and axillae, and they may be tearful, which can suggest depression. Before a diagnosis of anxiety disorder is made, physicians must rule out drug-induced anxiety and other medical causes.

In children GAD may be associated with headaches, restlessness, abdominal pain, and heart palpitations. Typically it begins around 8 to 9 years of age.

The single largest category of anxiety disorders is that of specific phobias which includes all cases in which fear and anxiety are triggered by a specific stimulus or situation. Between 5% and 12% of the population worldwide suffer from specific phobias. Sufferers typically anticipate terrifying consequences from encountering the object of their fear, which can be anything from an animal to a location to a bodily fluid to a particular situation. Common phobias are flying, blood, water, highway driving, and tunnels. When people are exposed to their phobia, they may experience trembling, shortness of breath, or rapid heartbeat. People understand that their fear is not proportional to the actual potential danger but still are overwhelmed by it.

Panic disorder sufferers usually have a series of intense episodes of extreme anxiety during panic attacks. These attacks typically last about ten minutes, and can be as short-lived as 1–5 minutes, but can last twenty minutes to more than an hour, or until helpful intervention is made. Panic attacks can wax and wane for a period of hours (panic attacks rolling into one another), and the intensity and specific symptoms of panic may vary over the duration.

In some cases, the attack may continue at unabated high intensity, or seem to be increasing in severity. Common symptoms of an attack include rapid heartbeat, perspiration, dizziness, dyspnea, trembling, uncontrollable fear such as: the fear of losing control and going crazy, the fear of dying and hyperventilation. Other symptoms are sweating, a sensation of choking, paralysis, chest pain, nausea, numbness or tingling, chills or hot flashes, faintness, crying and some sense of altered reality. In addition, the person usually has thoughts of impending doom. Individuals suffering from an episode have often a strong wish of escaping from the situation that provoked the attack. The anxiety of panic disorder is particularly severe and noticeably episodic compared to that from generalized anxiety disorder. Panic attacks may be provoked by exposure to certain stimuli (e.g., seeing a mouse) or settings (e.g., the dentist's office). Other attacks may appear unprovoked. Some individuals deal with these events on a regular basis, sometimes daily or weekly. The outward symptoms of a panic attack often cause negative social experiences (e.g., embarrassment, social stigma, social isolation, etc.).

Limited symptom attacks are similar to panic attacks, but have fewer symptoms. Most people with PD experience both panic attacks and limited symptom attacks.

Studies investigating the relationship between interoception and panic disorder have shown that people with panic disorder feel heartbeat sensations more intensely when stimulated by pharmacological agents, suggesting that they experience heightened interoceptive awareness compared to healthy subjects.

As with other anxiety disorders, children with SAD face more obstacles at school than those without anxiety disorders. Adjustment and relating school functioning have been found to be much more difficult for anxious children. In some severe forms of SAD, children may act disruptively in class or may refuse to attend school altogether. It is estimated that nearly 75% of children with SAD exhibit some form of school refusal behavior.

This is a serious problem because, as children fall further behind in coursework, it becomes increasingly difficult for them to return to school.

Short-term problems resulting from academic refusal include poor academic performance or decline in performance, alienation from peers, and conflict within the family.

Although school refusal behavior is common among children with SAD, it is important to note that school refusal behavior is sometimes linked to generalized anxiety disorder or possibly a mood disorder. That being said, a majority of children with separation anxiety disorder have school refusal as a symptom. Up to 80% of children who refuse school qualify for a diagnosis of separation anxiety disorder.

Just how SAD affects a child's attendance and participation in school, their avoidance behaviors stay with them as they grow and enter adulthood. Recently, "the effects of mental illness on workplace productivity have become a prominent concern on both the national and international fronts". In general, mental illness is a common health problem among working adults, 20 to 30% of adults will suffer from at least one psychiatric disorder. Mental illness is linked to decreased productivity, and with individuals diagnosed with SAD their levels at which they function decreases dramatically resulting in partial work-days, increase in number of total absences, and "holding back" when it comes to carrying out and completing tasks.

Generalized anxiety disorder (GAD) is an anxiety disorder characterized by excessive, uncontrollable and often irrational worry, that is, apprehensive expectation about events or activities. This excessive worry often interferes with daily functioning, as individuals with GAD typically anticipate disaster, and are overly concerned about everyday matters such as health issues, money, death, family problems, friendship problems, interpersonal relationship problems, or work difficulties. Individuals may exhibit a variety of physical symptoms, including feeling tired, fidgeting, headaches, numbness in hands and feet, muscle tension, difficulty swallowing, upset stomach, vomiting, diarrhea, breathing difficulty, difficulty concentrating, trembling, irritability, sweating, restlessness, sleeping difficulties, hot flashes, rashes, and inability to fully control the anxiety (ICD-10). These symptoms must be consistent and ongoing, persisting at least six months, for a formal diagnosis of GAD.

Standardized rating scales such as GAD-7 can be used to assess severity of GAD symptoms. GAD is the most common cause of disability in the workplace in the United States.

In a given year, approximately two percent of American adults and European adults experience GAD. Globally about 4% are affected at some point in their life. GAD is seen in women twice as much as men. GAD is also common in individuals with a history of substance abuse and a family history of the disorder. Once GAD develops, it may become chronic, but can be managed or eliminated with proper treatment.

The DSM-IV criteria stated that an individual cannot receive a diagnosis of social anxiety disorder if their symptoms are better accounted for by one of the autism spectrum disorders such as autism and Asperger syndrome.

Because of its close relationship and overlapping symptoms, treating people with social phobia may help to understand the underlying connections to other mental disorders. Social anxiety disorder is often linked to bipolar disorder and attention deficit hyperactivity disorder (ADHD) and some believe that they share an underlying cyclothymic-anxious-sensitive disposition. The co-occurrence of ADHD and social phobia is very high; especially when SCT symptoms are present.

In cognitive models of social anxiety disorder, those with social phobias experience dread over how they will be presented to others. They may feel overly self-conscious, pay high self-attention after the activity, or have high performance standards for themselves. According to the social psychology theory of self-presentation, a sufferer attempts to create a well-mannered impression towards others but believes he or she is unable to do so. Many times, prior to the potentially anxiety-provoking social situation, sufferers may deliberately review what could go wrong and how to deal with each unexpected case. After the event, they may have the perception that they performed unsatisfactorily. Consequently, they will perceive anything that may have possibly been abnormal as embarrassing. These thoughts may extend for weeks or longer. Cognitive distortions are a hallmark, and are learned about in CBT (cognitive-behavioral therapy). Thoughts are often self-defeating and inaccurate. Those with social phobia tend to interpret neutral or ambiguous conversations with a negative outlook, and many studies suggest that socially anxious individuals remember more negative memories than those less distressed.

An example of an instance may be that of an employee presenting to their co-workers. During the presentation, the person may stutter a word, upon which he or she may worry that other people significantly noticed and think that their perceptions of him or her as a presenter have been tarnished. This cognitive thought propels further anxiety which compounds with further stuttering, sweating, and, potentially, a panic attack.

Genes are attributed about a third of general anxiety disorder's variance. Individuals with a genetic predisposition for GAD are more likely to develop GAD, especially in response to a life stressor.

People who have repeated, persistent attacks or feel severe anxiety about having another attack are said to have panic disorder. Panic disorder is strikingly different from other types of anxiety disorders in that panic attacks are often sudden and unprovoked. However, panic attacks experienced by those with panic disorder may also be linked to or heightened by certain places or situations, making daily life difficult.

People with panic attacks often report a fear of dying or heart attack, flashing vision, faintness or nausea, numbness throughout the body, heavy breathing and hyperventilation, or loss of body control. Some people also suffer from tunnel vision, mostly due to blood flow leaving the head to more critical parts of the body in defense. These feelings may provoke a strong urge to escape or flee the place where the attack began (a consequence of the "fight-or-flight response", in which the hormone causing this response is released in significant amounts). This response floods the body with hormones, particularly epinephrine (adrenaline), which aid it in defending against harm.

A panic attack is a response of the sympathetic nervous system (SNS). The most common symptoms include trembling, dyspnea (shortness of breath), heart palpitations, chest pain (or chest tightness), hot flashes, cold flashes, burning sensations (particularly in the facial or neck area), sweating, nausea, dizziness (or slight vertigo), light-headedness, hyperventilation, paresthesias (tingling sensations), sensations of choking or smothering, difficulty moving, and derealization. These physical symptoms are interpreted with alarm in people prone to panic attacks. This results in increased anxiety and forms a positive feedback loop.

Often, the onset of shortness of breath and chest pain are the predominant symptoms. People with a panic attack may incorrectly attribute them to a heart attack and thus trigger seeking treatment in an emergency room. However, since chest pain and shortness of breath are indeed hallmark symptoms of cardiovascular illnesses, including unstable angina and myocardial infarction (heart attack), especially in a person whose mental health status and heart health status are not known, attributing these pains to simple anxiety and not (also) a physical condition is a diagnosis of exclusion (other conditions must be ruled out first) until an electrocardiogram and a mental health assessment have been carried out.

Panic attacks are distinguished from other forms of anxiety by their intensity and their sudden, episodic nature. They are often experienced in conjunction with anxiety disorders and other psychological conditions, although panic attacks are not generally indicative of a mental disorder.

Hypochondriasis is categorized as a somatic amplification disorder—a disorder of "perception and cognition"—that involves a hyper-vigilance of situation of the body or mind and a tendency to react to the initial perceptions in a negative manner that is further debilitating. Hypochondriasis manifests in many ways. Some people have numerous intrusive thoughts and physical sensations that push them to check with family, friends, and physicians. For example, a person who has a minor cough may think that they have tuberculosis. Or sounds produced by organs in the body, such as those made by the intestines, might be seen as a sign of a very serious illness to patients dealing with hypochondriasis.

Other people are so afraid of any reminder of illness that they will avoid medical professionals for a seemingly minor problem, sometimes to the point of becoming neglectful of their health when a serious condition may exist and go undiagnosed. Yet others live in despair and depression, certain that they have a life-threatening disease and no physician can help them. Some consider the disease as a punishment for past misdeeds.

Hypochondriasis is often accompanied by other psychological disorders. Bipolar disorder, clinical depression, obsessive-compulsive disorder (OCD), phobias, and somatization disorder are the most common accompanying conditions in people with hypochondriasis, as well as a generalized anxiety disorder diagnosis at some point in their life.

Many people with hypochondriasis experience a cycle of intrusive thoughts followed by compulsive checking, which is very similar to the symptoms of obsessive-compulsive disorder. However, while people with hypochondriasis are afraid of having an illness, patients with OCD worry about getting an illness or of transmitting an illness to others. Although some people might have both, these are distinct conditions.

Patients with hypochondriasis often are not aware that depression and anxiety produce their own physical symptoms, and mistake these symptoms for manifestations of another mental or physical disorder or disease. For example, people with depression often experience changes in appetite and weight fluctuation, fatigue, decreased interest in sex and motivation in life overall. Intense anxiety is associated with rapid heartbeat, palpitations, sweating, muscle tension, stomach discomfort, dizziness, and numbness or tingling in certain parts of the body (hands, forehead, etc.).

In some cases, hypochondriasis responds well to antipsychotics, particularly the newer atypical antipsychotic medication.

If a person is ill with a medical disease such as diabetes or arthritis, there will often be psychological consequences, such as depression. Some even report being suicidal. In the same way, someone with psychological issues such as depression or anxiety will sometimes experience physical manifestations of these affective fluctuations, often in the form of medically unexplained symptoms. Common symptoms include headaches; abdominal, back, joint, rectal, or urinary pain; nausea; fever and/or night sweats; itching; diarrhea; dizziness; or balance problems. Many people with hypochondriasis accompanied by medically unexplained symptoms feel they are not understood by their physicians, and are frustrated by their doctors’ repeated failure to provide symptom relief.

A somatic symptom disorder, formerly known as a somatoform disorder, is any mental disorder which manifests as physical symptoms that suggest illness or injury, but which cannot be explained fully by a general medical condition or by the direct effect of a substance, and are not attributable to another mental disorder (e.g., panic disorder). Somatic symptom disorders, as a group, are included in a number of diagnostic schemes of mental illness, including the "Diagnostic and Statistical Manual of Mental Disorders". (Before DSM-5 this disorder was split into "somatization disorder" and "undifferentiated somatoform disorder".)

In people who have been diagnosed with a somatic symptom disorder, medical test results are either normal or do not explain the person's symptoms, and history and physical examination do not indicate the presence of a known medical condition that could cause them, though it is important to note that the DSM-5 cautions that this alone is not sufficient for diagnosis. The patient must also be excessively worried about their symptoms, and this worry must be judged to be out of proportion to the severity of the physical complaints themselves. A diagnosis of somatic symptom disorder requires that the subject have recurring somatic complaints for at least six months.

Symptoms are sometimes similar to those of other illnesses and may last for years. Usually, the symptoms begin appearing during adolescence, and patients are diagnosed before the age of 30 years. Symptoms may occur across cultures and gender. Other common symptoms include anxiety and depression. However, since anxiety and depression are also very common in persons with confirmed medical illnesses, it remains possible that such symptoms are a consequence of the physical impairment, rather than a cause. Somatic symptom disorders are not the result of conscious malingering (fabricating or exaggerating symptoms for secondary motives) or factitious disorders (deliberately producing, feigning, or exaggerating symptoms). Somatic symptom disorder is difficult to diagnose and treat. Some advocates of the diagnosis believe this is because proper diagnosis and treatment requires psychiatrists to work with neurologists on patients with this disorder.

Somatic symptom disorders are a group of disorders, all of which fit the definition of physical symptoms similar to those observed in physical disease or injury for which there is no identifiable physical cause. As such, they are a diagnosis of exclusion. Somatic symptoms may be generalized in four major medical categories: neurological, cardiac, pain, and gastrointestinal somatic symptoms.

Hyperthyroidism is a condition in which the thyroid gland produces too much thyroid hormone, thyroxin. This overabundance of thyroxin causes irregular and rapid heartbeat, irritability, weight loss, nervousness, anxiety and racing thoughts.

The anxiety and inability to focus is very common in hyperthyroidism and leads to racing thoughts, as well as panic attacks and difficulty concentrating.

The causes of racing thoughts are most often associated with anxiety disorders, but many influences can cause these rapid, racing thoughts. There are also many associated conditions, in addition to anxiety disorders, which can be classified as having secondary relationships with causing racing thoughts. The conditions most commonly linked to racing thoughts are bipolar disorder, anxiety disorder, attention deficit hyperactivity disorder, sleep deprivation, amphetamine dependence, and hyperthyroidism.

Agoraphobia is a condition where sufferers become anxious in unfamiliar environments or where they perceive that they have little control. Triggers for this anxiety may include wide-open spaces, crowds (social anxiety), or traveling (even short distances). Agoraphobia is often, but not always, compounded by a fear of social embarrassment, as the agoraphobic fears the onset of a panic attack and appearing distraught in public. Most of the time they avoid these areas and stay in the comfort of their safe haven. This is also sometimes called "social agoraphobia", which may be a subtype of social anxiety disorder.

Agoraphobia is also defined as "a fear, sometimes terrifying, by those who have experienced one or more panic attacks". In these cases, the sufferer is fearful of a particular place because they have experienced a panic attack at the same location at a previous time. Fearing the onset of another panic attack, the sufferer is fearful or even avoids a location. Some refuse to leave their homes even in medical emergencies because the fear of being outside of their comfort areas is too great.

The sufferers can sometimes go to great lengths to avoid the locations where they have experienced the onset of a panic attack. Agoraphobia, as described in this manner, is actually a symptom professionals check when making a diagnosis of panic disorder. Other syndromes like obsessive compulsive disorder or post-traumatic stress disorder can also cause agoraphobia. Essentially, any irrational fear that keeps one from going outside can cause the syndrome.

Agoraphobics may suffer from temporary separation anxiety disorder when certain other individuals of the household depart from the residence temporarily, such as a parent or spouse, or when the agoraphobic is left home alone. Such temporary conditions can result in an increase in anxiety or a panic attack or feeling the need to separate themselves from family or maybe friends.

Another common associative disorder of agoraphobia is thanatophobia, the fear of death. The anxiety level of agoraphobics often increases when dwelling upon the idea of eventually dying, which they may consciously or unconsciously associate with being the ultimate separation from their emotional comfort and safety zones and loved ones, even for those who may otherwise believe in some form of afterlife.

Agoraphobia is an anxiety disorder characterized by symptoms of anxiety in situations where the person perceives the environment to be unsafe with no easy way to get away. These situations can include open spaces, public transit, shopping malls, or simply being outside the home. Being in these situations may result in a panic attack. The symptoms occur nearly every time the situation is encountered and last for more than six months. Those affected will go to great lengths to avoid these situations. In severe cases people may become unable to leave their homes.

Agoraphobia is believed to be due to a combination of genetic and environmental factors. The condition often runs in families, and stressful events such as the death of a parent or being attacked may be a trigger. In the DSM-5 agoraphobia is classified as a phobia along with specific phobias and social phobia. Other conditions that can produce similar symptoms include separation anxiety, posttraumatic stress disorder, and major depressive disorder. Those affected are at higher risk of depression and substance use disorder.

Without treatment it is uncommon for agoraphobia to resolve. Treatment is typically with a type of counselling called cognitive behavioral therapy (CBT). CBT results in resolution for about half of people. Agoraphobia affects about 1.7% of adults. Women are affected about twice as often as men. The condition often begins in early adulthood and becomes less common in old age. It is rare in children. The term "agoraphobia" is from Greek ἀγορά, "agorá", meaning a "public square" and -φοβία, "-phobia", meaning "fear".

Hypochondriasis or hypochondria is a condition in which a person is inordinately worried about having a serious illness. An old concept, its meaning has repeatedly changed due to redefinitions in its source metaphors. It has been claimed that this debilitating condition results from an inaccurate perception of the condition of body or mind despite the absence of an actual medical diagnosis. An individual with hypochondriasis is known as a hypochondriac. Hypochondriacs become unduly alarmed about any physical or psychological symptoms they detect, no matter how minor the symptom may be, and are convinced that they have, or are about to be diagnosed with, a serious illness.

Often, hypochondria persists even after a physician has evaluated a person and reassured them that their concerns about symptoms do not have an underlying medical basis or, if there is a medical illness, their concerns are far in excess of what is appropriate for the level of disease. Many hypochondriacs focus on a particular symptom as the catalyst of their worrying, such as gastro-intestinal problems, palpitations, or muscle fatigue. To qualify for the diagnosis of hypochondria the symptoms must have been experienced for at least 6 months.

The DSM-IV-TR defines this disorder, "Hypochondriasis", as a somatoform disorder and one study has shown it to affect about 3% of the visitors to primary care settings. The newly published DSM-5 replaces the diagnosis of hypochondriasis with the diagnoses of "somatic symptom disorder" and "illness anxiety disorder".

Hypochondria is often characterized by fears that minor bodily or mental symptoms may indicate a serious illness, constant self-examination and self-diagnosis, and a preoccupation with one's body. Many individuals with hypochondriasis express doubt and disbelief in the doctors' diagnosis, and report that doctors’ reassurance about an absence of a serious medical condition is unconvincing, or short-lasting. Additionally, many hypochondriacs experience elevated blood pressure, stress, and anxiety in the presence of doctors or while occupying a medical facility, a condition known as "white coat syndrome". Many hypochondriacs require constant reassurance, either from doctors, family, or friends, and the disorder can become a debilitating challenge for the individual with hypochondriasis, as well as his or her family and friends. Some hypochondriacal individuals completely avoid any reminder of illness, whereas others frequently visit medical facilities, sometimes obsessively. Some sufferers may never speak about it.

Behaviors that are apparent in those with internalizing disorders include depression, withdrawal, anxiety, and loneliness. There are also behavioral characteristics involved with internalizing disorders. Some behavioral abnormalities include poor self-esteem, suicidal behaviors, decreased academic progress, and social withdrawal. Internalizing one's problems, like sadness, can cause the problems to grow into larger burdens such as social withdrawal, suicidal behaviors or thoughts, and other unexplained physical symptoms.

The internalizing disorders, with high levels of negative affectivity, include depressive disorders, anxiety disorders, obsessive-compulsive and related disorders, trauma and stressor-related disorders, and dissociative disorders. Others like bulimia, and anorexia also come under this category.

A person may be diagnosed with taijin kyofusho if they feel as if their attitudes, behavior, and physical characteristics are inadequate in social situations. As a result of these feelings, they also experience persistent suffering in the form of emotional distress through shame, embarrassment, anxiety, fear, and other tense feelings that occur when confronted with social circumstances. In addition, individuals also worry about being unable to maintain healthy relationships with others. When it comes to socializing, taijin kyofusho sufferers avoid painful social and interpersonal situations, while simultaneously being averse to doing so. Those likely to develop taijin kyofusho have more of a temperamental characteristic of being hypochondriacal. The balance between introversion and extroversion in hypochondriacal temperament is geared more towards introversion. The introversion causes sufferers to focus on themself and problems they have, and by fixating on their weaknesses they become more anxious and depressed.

The affective spectrum is a spectrum of affective disorders (mood disorders). It is a grouping of related psychiatric and medical disorders which may accompany bipolar, unipolar, and schizoaffective disorders at statistically higher rates than would normally be expected. These disorders are identified by a common positive response to the same types of pharmacologic treatments. They also aggregate strongly in families and may therefore share common heritable underlying physiologic anomalies.

Affective spectrum disorders include:

- Attention deficit hyperactivity disorder

- Bipolar disorder

- Body dysmorphic disorder

- Bulimia nervosa and other eating disorders

- Cataplexy

- Dysthymia

- Generalized anxiety disorder

- Hypersexuality

- Irritable bowel syndrome

- Impulse-control disorders

- Kleptomania

- Migraine

- Major depressive disorder

- Obsessive-compulsive disorder

- Oppositional defiant disorder

- Panic disorder

- Posttraumatic stress disorder

- Premenstrual dysphoric disorder

- Social anxiety disorder

- Fibromyalgia

The following may also be part of the spectrum accompanying affective disorders.

- Chronic pain

- Intermittent explosive disorder

- Pathological gambling

- Personality disorder

- Pyromania

- Substance abuse and addiction (includes alcoholism)

- Trichotillomania

Also, there are now studies linking heart disease.

Many of the terms above overlap. The American Psychiatric Association's definitions of these terms can be found in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM).

International Statistical Classification of Diseases and Related Health Problems, mostly known as "ICD", assigns codes to classify diseases, symptoms, complaints, social behaviors, injuries, and such medical-related findings.

ICD 10 classifies adjustment disorders under F40-F48 and under neurotic, stress-related and somatoform disorders.