The cause of dog separation anxiety is unknown, but may be triggered by:

- a traumatic event

- a change in routine

- major life change (e.g., new home, new baby, death of a family member, abandonment to a shelter)

- extreme attachment or dependency on the owner

One cause of separation anxiety in canines is chronic stress. A study in 2012 tested nelumbinis semen, the seeds of the herb "Nelumbo nucifera", and its anti-depressant effects on animals experiencing stress. It should be noted that this study did not test directly on canines, but rather rats, and aimed to apply the principles found by the study to other animals such as dogs. The study, however, did test oral toxicity specifically on canines. After testing different dosage amounts of the nelumbinis semen, scientists determined that 400 mg per the animal's weight in kilograms was the most ideal amount to lower immobility when the animal was faced with a stressful situation. In addition, nelumbinis semen was not found toxic when administered to dogs. Based on these findings, it is possible that if more research was put into studying herbal remedies such as nelumbinis semen, it is possible that alternative and "natural" ingredients could be used as a substitute for drug-based therapy.

Anxiety disorders are the most common type of psychopathology to occur in today's youth, affecting from 5–25% of children worldwide. Of these anxiety disorders, SAD accounts for a large proportion of diagnoses. SAD may account for up to 50% of the anxiety disorders as recorded in referrals for mental health treatment. SAD is noted as one of the earliest-occurring of all anxiety disorders. Adult separation anxiety disorder affects roughly 7% of adults. It has also been reported that the clinically anxious pediatric population are considerably larger. For example, according to Hammerness et al. (2008) SAD accounted for 49% of admissions.

Research suggests that 4.1% of children will experience a clinical level of separation anxiety. Of that 4.1% it is calculated that nearly a third of all cases will persist into adulthood if left untreated. Research continues to explore the implications that early dispositions of SAD in childhood may serve as risk factors for the development of mental disorders throughout adolescence and adulthood. It is presumed that a much higher percentage of children suffer from a small amount of separation anxiety, and are not actually diagnosed. Multiple studies have found higher rates of SAD in girls than in boys, and that paternal absence may increase the chances of SAD in girls.

Several studies aim to understand the long-term mental health consequences of SAD. SAD contributed to vulnerability and acted as a strong risk factor for developing other mental disorders in people aged 19–30. Specifically disorders including panic disorder and depressive disorders were more likely to occur. Other sources also support the increased likelihood of displaying either of the two psychopathologies with previous history of childhood SAD.

Panic disorder typically begins during early adulthood; roughly half of all people who have panic disorder develop the condition before age 24, especially those subjected to traumatic experiences. However, some sources say that the majority of young people affected for the first time are between the ages of 25 and 30. Women are twice as likely as men to develop panic disorder and it occurs more often in people with above average intelligence.

Panic disorder can continue for months or years, depending on how and when treatment is sought. If left untreated, it may worsen to the point where one's life is seriously affected by panic attacks and by attempts to avoid or conceal the condition. In fact, many people have had problems with personal relationships or employment while struggling to cope with panic disorder. Some people with panic disorder may conceal their condition because of the stigma of mental illness. In some individuals, symptoms may occur frequently for a period of months or years, then many years may pass without symptoms. In some cases, the symptoms persist at the same level indefinitely. There is also some evidence that many individuals (especially those who develop symptoms at an early age) may experience symptom cessation later in life (e.g. past age 50).

In 2000, the World Health Organization found prevalence and incidence rates for panic disorder to be very similar across the globe. Age-standardized prevalence per 100,000 ranged from 309 in Africa to 330 in East Asia for men and from 613 in Africa to 649 in North America, Oceania, and Europe for women.

Factors that can cause reluctance to attend school can be divided into four categories. These categories have been developed based on studies in the United States under the leadership of Professor Christopher Kearney. Some students may be affected by several factors at once.

- The child might want to be free.

- The child possibly wants to avoid school-related issues and situations that cause them to experience unpleasant feelings, such as anxiety, depression, or psychosomatic symptoms. The reluctance to attend school is one symptom that can indicate the presence of a larger issue, such as anxiety disorder, depression, learning disability, sleep disorder, separation anxiety or panic disorder.

- The child may want to avoid tests, presentations, group work, specific lessons, or interaction with other children. The child should be assessed for learning disabilities if academic performance is average or low.

- The child may want attention from significant people outside of school, such as parents or older acquaintances.

- The child possibly wants to do something more enjoyable outside of school, like practice hobbies, play computer games, watch movies, play with friends such as riding bikes, etc., or learn autodidactictally.

Other factors can be:

- Anxiety about academic achievement and being tested can arise on the basis of inflated claims by teachers and/or parents, but also unrealistic ambitions of the upset child themselves.

- School refusal may arise as a response to bullying or peer rejection.

- Shyness or a social phobia can contribute to school refusal.

- The child might worry about parents or siblings, for instance, a parent with substance abuse, or a parent who physically abuses other family members.

- Some students may refuse to go to school due to anxiety or fears of emergency drills, such as fire, lockdown, and tornado drills.

GAD runs in families and is six times more common in the children of someone with the condition.

While anxiety arose as an adaptation, in modern times it is almost always thought of negatively in the context of anxiety disorders. People with these disorders have highly sensitive systems; hence, their systems tend to overreact to seemingly harmless stimuli. Sometimes anxiety disorders occur in those who have had traumatic youths, demonstrating an increased prevalence of anxiety when it appears a child will have a difficult future. In these cases, the disorder arises as a way to predict that the individual’s environment will continue to pose threats.

Approximately 1 to 5% of school-aged children have school refusal, though it is most common in 5- and 6-year olds and in 10- and 11-year olds, it occurs more frequently during major changes in a child’s life, such as entrance to kindergarten, changing from elementary to middle school, or changing from middle to high school. The problem may start following vacations, school holidays, summer vacation, or brief illness, after the child has been home for some time, and usually ends prior to vacations, school holidays, or summer vacation, before the child will be out of school for some time. School refusal can also occur after a stressful event, such as moving to a new house, or the death of a pet or relative.

The rate is similar within both genders, and although it is significantly more prevalent in some urban areas, there are no known socioeconomic differences.

At a low level, anxiety is not a bad thing. In fact, the hormonal response to anxiety has evolved as a benefit, as it helps humans react to dangers. Researchers in evolutionary medicine believe this adaptation allows humans to realize there is a potential threat and to act accordingly in order to ensure greatest possibility of protection. It has actually been shown that those with low levels of anxiety have a greater risk of death than those with average levels. This is because the absence of fear can lead to injury or death. Additionally, patients with both anxiety and depression were found to have lower morbidity than those with depression alone. The functional significance of the symptoms associated with anxiety includes: greater alertness, quicker preparation for action, and reduced probability of missing threats. In the wild, vulnerable individuals, for example those who are hurt or pregnant, have a lower threshold for anxiety response, making them more alert. This demonstrates a lengthy evolutionary history of the anxiety response.

Specific phobias have a one-year prevalence of 8.7% in the USA with 21.9% of the cases being severe, 30.0% moderate and 48.1% mild. The usual age of onset is childhood to adolescence. Women are twice as likely to suffer from specific phobias as men.

Evolutionary psychology argues that infants or children develop specific phobias to things that could possibly harm them, so their phobias alert them to the danger.

The most common co-occurring disorder for children with a specific phobia is another anxiety disorder. Although comorbidity is frequent for children with specific phobias, it tends to be lower than for other anxiety disorders.

Onset is typically between 7 and 9 years of age. Specific phobias can occur at any age but seem to peak between 10 and 13 years of age.

According to Child and Adolescent Mental Health, approximately 5 percent of children suffer from specific phobias and 15 percent seek treatment for anxiety-related problems. In recent years the number of children with clinically diagnosed phobias has gradually increased. Researchers are finding that the majority of these diagnoses come anxiety related phobias or society phobias.

Specific phobias are more prevalent in girls than in boys. Likewise, specific phobias are also more prevalent in older children than younger.

Though some fears are inborn, the majority are learned. Phobias develop through negative experiences and through observation. One way children begin to develop fears is by witnessing or hearing about dangers. Ollendick proposes while some phobias may originate from a single traumatizing experience, others may be caused by simpler, or less dramatic, origins such as observing another child’s phobic reaction or through the exposure to media that introduces phobias.

- 2% of parents linked their child’s phobia to a [direct conditioning episode]

- 26% of parents linked their child’s phobia to a [vicarious conditioning episodes]

- 56% of parents linked their child’s phobia to their child’s very first contact with water

- 16% of parents could not directly link their child’s phobia

In addition to asking about the origins of a child’s fear, the questionnaire asked if parents believed that “information associated with adverse consequences was the most influential factor in the development of their child’s phobia.” The results were as followed:

- 0% of parents though it was the most influential factor

- 14% of parents though it was somewhat influential

- 86% of parents though it had little to no influence

Hypochondria is currently considered a psychosomatic disorder, as in a mental illness with physical symptoms. Cyberchondria is a colloquial term for hypochondria in individuals who have researched medical conditions on the Internet. The media and the Internet often contribute to hypochondria, as articles, TV shows and advertisements regarding serious illnesses such as cancer and multiple sclerosis often portray these diseases as being random, obscure and somewhat inevitable. Inaccurate portrayal of risk and the identification of non-specific symptoms as signs of serious illness contribute to exacerbating the hypochondriac’s fear that they actually have that illness.

Major disease outbreaks or predicted pandemics can also contribute to hypochondria. Statistics regarding certain illnesses, such as cancer, will give hypochondriacs the illusion that they are more likely to develop the disease.

Overly protective caregivers and an excessive focus on minor health concerns have been implicated as a potential cause of hypochondriasis development.

It is common for serious illnesses or deaths of family members or friends to trigger hypochondria in certain individuals. Similarly, when approaching the age of a parent's premature death from disease, many otherwise healthy, happy individuals fall prey to hypochondria. These individuals believe they are suffering from the same disease that caused their parent's death, sometimes causing panic attacks with corresponding symptoms.

Family studies of hypochondriasis do not show a genetic transmission of the disorder. Among relatives of people suffering from hypochondriasis only somatization disorder and generalized anxiety disorder were more common than in average families. Other studies have shown that the first degree relatives of patients with OCD have a higher than expected frequency of a somatoform disorder (either hypochondriasis or body dysmorphic disorder).

A number of clinical studies have shown a positive association between caffeine ingestion and panic disorder and/or anxiogenic effects. People who have panic disorder are more sensitive to the anxiety-provoking effects of caffeine. One of the major anxiety-provoking effects of caffeine is an increase in heart rate.

Certain cold and flu medications containing decongestants may also contain pseudoephedrine, ephedrine, phenylephrine, naphazoline and oxymetazoline. These may be avoided by the use of decongestants formulated to prevent causing high blood pressure.

Various factors have been found to be more associated with a diagnosis of AD than other axis I disorders, including:

- younger age

- more identified psychosocial and environmental problems

- increased suicidal behaviour, more likely to be rated as improved by the time of discharge from mental healthcare

- less frequent previous psychiatric history

- shorter length of treatment

Those exposed to repeated trauma are at greater risk, even if that trauma is in the distant past. Age can be a factor due to young children having fewer coping resources; children are also less likely to assess the consequences of a potential stressor.

A stressor is generally an event of a serious, unusual nature that an individual or group of individuals experience. The stressors that cause adjustment disorders may be grossly traumatic or relatively minor, like loss of a girlfriend/boyfriend, a poor report card, or moving to a new neighborhood. It is thought that the more chronic or recurrent the stressor, the more likely it is to produce a disorder. The objective nature of the stressor is of secondary importance. Stressors' most crucial link to their pathogenic potential is their perception by the patient as stressful. The presence of a causal stressor is essential before a diagnosis of adjustment disorder can be made.

There are certain stressors that are more common in different age groups:

Adulthood:

- Marital conflict

- Financial conflict

- Health issues with Oneself/Partner or Dependent children

- Personal tragedy (Death/personal loss)

- Loss of job or unstable employment conditions (e.g. Corporate takeover/redundancy)

Adolescence and childhood:

- Family conflict/parental separation

- School problems/changing schools

- Sexuality issues

- Death/illness/trauma in the family

In a study conducted from 1990 to 1994 on 89 psychiatric outpatient adolescents, 25% had attempted suicide in which 37.5% had misused alcohol, 87.5% displayed aggressive behaviour, 12.5% had learning difficulties, and 87.5% had anxiety symptoms.

Agoraphobia occurs about twice as commonly among women as it does in men. The gender difference may be attributable to several factors: sociocultural traditions that encourage, or permit, the greater expression of avoidance coping strategies by women (including dependent and helpless behaviors), women perhaps being more likely to seek help and therefore be diagnosed, and men being more likely to abuse alcohol in reaction to anxiety and be diagnosed as an alcoholic. Research has not yet produced a single clear explanation for the gender difference in agoraphobia.

Panic disorder with or without agoraphobia affects roughly 5.1% of Americans, and about 1/3 of this population with panic disorder have comorbid agoraphobia. It is uncommon to have agoraphobia without panic attacks, with only 0.17% of people with agorophobia not presenting panic disorders as well.

Chronic use of tranquilizers and sleeping pills such as benzodiazepines has been linked to onset of agoraphobia. In 10 patients who had developed agoraphobia during benzodiazepine dependence, symptoms abated within the first year of assisted withdrawal. Similarly, alcohol use disorders are associated with panic with or without agoraphobia; this association may be due to the long-term effects of alcohol misuse causing a distortion in brain chemistry.

Tobacco smoking has also been associated with the development and emergence of agoraphobia, often with panic disorder; it is uncertain how tobacco smoking results in anxiety-panic with or without agoraphobia symptoms, but the direct effects of nicotine dependence or the effects of tobacco smoke on breathing have been suggested as possible causes. Self-medication or a combination of factors may also explain the association between tobacco smoking and agoraphobia and panic.

Risk factors (constructs which increase the likelihood or intensity of homesickness) and protective factors (constructs that decrease the likelihood or intensity of homesickness) vary by population. For example, a seafarers on board, the environmental stressors associated with a hospital, a military boot camp or a foreign country may exacerbate homesickness and complicate treatment. Generally speaking, however, risk and protective factors transcend age and environment.

Most research indicates that cognitive behavioral therapy (CBT) is an effective treatment for hypochondriasis. Much of this research is limited by methodological issues. A small amount of evidence suggests that selective serotonin reuptake inhibitors can also reduce symptoms, but further research is needed.

According to the DSM IV-TR, the development of the emotional or behavioral symptoms of this diagnosis have to occur within three months of the onset of the identifiable stressor(s). Some emotional signs of adjustment disorder are:

However, the stress-related disturbance does not only exist as an exacerbation of a pre-existing axis I or axis II disorder and cannot be diagnostic as axis 1 disorder.

Suicidal behavior is prominent among people with AD of all ages, and up to one-fifth of adolescent suicide victims may have an adjustment disorder. Bronish and Hecht (1989) found that 70% of a series of patients with AD attempted suicide immediately before their index admission and they remitted faster than a comparison group with major depression. Asnis et al. (1993) found that AD patients report persistent ideation or suicide attempts less frequently than those diagnosed with major depression. According to a study on 82 AD patients at a clinic, Bolu et al. (2012) found that 22 (26.8%) of these patients were admitted due to suicide attempt, consistent with previous findings. In addition, it was found that 15 of these 22 patients chose suicide methods that involved high chances of being saved. Henriksson et al. (2005) states statistically that the stressors are of one-half related to parental issues and one-third in peer issues.

The risk factors for homesickness fall into five categories: experience, personality, family, attitude and environment. More is known about some of these factors in adults—especially personality factors—because more homesickness research has been performed with older populations. However, a growing body of research is elucidating the etiology of homesickness in younger populations, including children at summer camp, hospitalized children and students.

- Experience factors: Younger age; little previous experience away from home (for which age can be a proxy); little or no previous experience in the novel environment; little or no previous experience venturing out without primary caregivers.

- Attitude factors: The belief that homesickness will be strong; negative first impressions and low expectations for the new environment; perceived absence of social support; high perceived demands (e.g., on academic, vocational or sports performance); great perceived distance from home

- Personality factors: Insecure attachment relationship with primary caregivers; low perceived control over the timing and nature of the separation from home; anxious or depressed feelings in the months prior to the separation; low self-directedness; high harm avoidance; rigidity; a wishful-thinking coping style.

- Family factors: Low decision control (e.g., caregivers forcing a young child to spend time away from home against her wishes); governments forcing a person to be in a novel environment (e.g., being drafted into military service away from home or being sentenced to prison); unsupportive caregiving; caregivers who express anxiety or ambivalence about the separation (e.g., "Have a great time away. I don't know what I'll do without you.")

- Environmental factors: High cultural contrast (e.g., different language, customs, food); threats to physical and emotional safety; dramatic alternations in daily schedule; lack of information about the new place; perceived discrimination

Finally, research has provided no support for a few factors that conventional wisdom had once held to be risk factors. These include: recent separation or divorce of primary caregivers; geographic distance from home; or recent geographic move. Most likely, it is not a change in family structure, distance or dwelling that predicts homesickness, but whether these changes have left unanswered (potentially preoccupying) questions in the person's mind.

Some scholars believe that codependency is not a negative trait, and does not need to be treated, as it is more likely a healthy personality trait taken to excess. Codependency in nonclinical populations has some links with favourable characteristics of family functioning.

Stan Katz states that codependence is over-diagnosed, and that many people who could be helped with shorter-term treatments instead become dependent on long-term self-help programs. The language of, symptoms of, and treatment for codependence derive from the medical model suggesting a disease process underlies the behavior. However, there is no evidence that codependence is caused by a disease process.

In their book, “Attached.”, Dr. Amir Levine and Rachel S. F. Heller, address what they call the “codependency myth” by asserting that attachment theory is a more scientific and helpful model for understanding and dealing with attachment in adults.

Bruce and Sanderson also state that animal phobias are more common in females than males. Furthermore, Dr. B.K. Wiederhold, a psychiatrist investigating virtual reality therapy as a possible method of therapy for anxiety disorders, goes on to provide data that although prevalent in both men and women, 75% to 90% of patients reporting specific phobias of the animal subtype are women.

In 2007 scientists found astraphobia is the third most prevalent phobia in the US. It can occur in people of any age. It occurs in many children, and should not be immediately identified as a phobia because children naturally go through many fears as they mature. Their fear of thunder and lightning cannot be considered a fully developed phobia unless it persists for more than six months. In this case, the child's phobia should be addressed, for it may become a serious problem in adulthood.

To lessen a child's fear during thunderstorms, the child can be distracted by games and activities. A bolder approach is to treat the storm as an entertainment; a fearless adult is an excellent role model for children.

Fear of the dark is a common fear or phobia among children and, to a varying degree, adults.