DAI is the result of traumatic shearing forces that occur when the head is rapidly accelerated or decelerated, as may occur in car accidents, falls, and assaults. Vehicle accidents are the most frequent cause of DAI; it can also occur as the result of child abuse such as in shaken baby syndrome.

Immediate disconnection of axons could be observed in severe brain injury, but the major damage of DAI is delayed secondary axon disconnections slowly developed over an extended time course. Tracts of axons, which appear white due to myelination, are referred to as white matter. Lesions in both grey and white matters are found in postmortem brains in CT and MRI exams.

Besides mechanical breaking of the axonal cytoskeleton, DAI pathology also includes secondary physiological changes such as interrupted axonal transport, progressive swellings and degeneration. Recent studies have linked these changes to twisting and misalignment of broken axon microtubules, as well as tau and APP deposition.

Common causes of head injury are motor vehicle traffic collisions, home and occupational accidents, falls, and assaults. Wilson's disease has also been indicative of head injury. According to the United States CDC, 32% of traumatic brain injuries (another, more specific, term for head injuries) are caused by falls, 10% by assaults, 16.5% by being struck or against something, 17% by motor vehicle accidents, 21% by other/unknown ways. In addition, the highest rate of injury is among children ages 0–14 and adults age 65 and older.

Diffuse axonal injury (DAI) is a brain injury in which damage in the form of extensive lesions in white matter tracts occurs over a widespread area. DAI is one of the most common and devastating types of traumatic brain injury, and is a major cause of unconsciousness and persistent vegetative state after severe head trauma. It occurs in about half of all cases of severe head trauma and may be the primary damage that occurs in concussion. The outcome is frequently coma, with over 90% of patients with severe DAI never regaining consciousness. Those who do wake up often remain significantly impaired.

DAI can occur in every degree of severity from very mild or moderate to very severe. Concussion may be a milder type of diffuse axonal injury.

In children with uncomplicated minor head injuries the risk of intra cranial bleeding over the next year is rare at 2 cases per 1 million. In some cases transient neurological disturbances may occur, lasting minutes to hours. Malignant post traumatic cerebral swelling can develop unexpectedly in stable patients after an injury, as can post traumatic seizures. Recovery in children with neurologic deficits will vary. Children with neurologic deficits who improve daily are more likely to recover, while those who are vegetative for months are less likely to improve. Most patients without deficits have full recovery. However, persons who sustain head trauma resulting in unconsciousness for an hour or more have twice the risk of developing Alzheimer's disease later in life.

Head injury may be associated with a neck injury. Bruises on the back or neck, neck pain, or pain radiating to the arms are signs of cervical spine injury and merit spinal immobilization via application of a cervical collar and possibly a long board.If the neurological exam is normal this is reassuring. Reassessment is needed if there is a worsening headache, seizure, one sided weakness, or has persistent vomiting.

To combat overuse of Head CT Scans yielding negative intracranial hemorrhage, which unnecessarily expose patients to radiation and increase time in the hospital and cost of the visit, multiple clinical decision support rules have been developed to help clinicians weigh the option to scan a patient with a head injury. Among these are the Canadian Head CT rule, the PECARN Head Injury/Trauma Algorithm, and the New Orleans/Charity Head Injury/Trauma Rule all help clinicians make these decisions using easily obtained information and noninvasive practices.

The condition is thought to be under-reported in the medical literature. A study of 27 cases conducted by Timothy C Hain in 1999 noted all but one patient to be female. The average age in this series was 49 years. This apparent gender disparity, however, may be due in part to the fact that the questionnaire which formed the basis of the study was circulated in a publication with a predominantly female reader base.

Subsequent studies have produced conflicting results with regard to the gender distribution of MdDS. The trends in Hain's report have recently been supported by the MdDS Balance Disorder Foundation, in a study of over 100 individuals diagnosed with MdDS. The female:male ratio was approximately 9:1; the average age of onset was 43–45 years. However, another recent study found that 44% of subjects who had experienced MdDS for 2 years or more were male, suggesting a more even distribution.

It has been shown to occur in excursions of as little as 30 minutes though it has been unclear how long it takes for symptoms to occur. The most commonly reported inciting event was a prolonged ocean cruise (~45%); however, shorter boating excursions (~22%), aircraft travel (~15%), and automobile travel (~8%) have all been described.

Mal de Débarquement syndrome has been noted as far back to the times of Erasmus Darwin in 1796, and Irwin J A (1881) "The pathology of seasickness".

Cases of MdDS have been reported in children as young as eight and in both genders. Men may have a more difficult time obtaining a diagnosis due to the disparity of women reported. When sailors and soldiers returned from World War II, the syndrome was reported at a higher rate in males.

In persistent MdDS, the symptoms continue for more than a month, possibly years or indefinitely. The longer the disorder remains, there is a progressively lower likelihood of remission. All medical treatment is palliative for sufferers with persistent MdDS symptoms.

Although increasing numbers of childhood mental health problems are being attributed to genetic defects, reactive attachment disorder is by definition based on a problematic history of care and social relationships. Abuse can occur alongside the required factors, but on its own does not explain attachment disorder. It has been suggested that types of temperament, or constitutional response to the environment, may make some individuals susceptible to the stress of unpredictable or hostile relationships with caregivers in the early years. In the absence of available and responsive caregivers it appears that some children are particularly vulnerable to developing attachment disorders.

There is as yet no explanation for why similar abnormal parenting may produce the two distinct forms of the disorder, inhibited and disinhibited. The issue of temperament and its influence on the development of attachment disorders has yet to be resolved. RAD has never been reported in the absence of serious environmental adversity yet outcomes for children raised in the same environment vary widely.

In discussing the neurobiological basis for attachment and trauma symptoms in a seven-year twin study, it has been suggested that the roots of various forms of psychopathology, including RAD, Borderline Personality Disorder (BPD), and post-traumatic stress disorder (PTSD), can be found in disturbances in affect regulation. The subsequent development of higher-order self-regulation is jeopardized and the formation of internal models is affected. Consequently, the "templates" in the mind that drive organized behavior in relationships may be impacted. The potential for "re-regulation" (modulation of emotional responses to within the normal range) in the presence of "corrective" experiences (normative caregiving) seems possible.

Epidemiological data are limited, but reactive attachment disorder appears to be very uncommon. The prevalence of RAD is unclear but it is probably quite rare, other than in populations of children being reared in the most extreme, deprived settings such as some orphanages. There is little systematically gathered epidemiologic information on RAD. A cohort study of 211 Copenhagen children to the age of 18 months found a prevalence of 0.9%.

Attachment disorders tend to occur in a definable set of contexts such as within some types of institutions, in the presence of repeated changes of primary caregiver or of extremely neglectful identifiable primary caregivers who show persistent disregard for the child's basic attachment needs, but not all children raised in these conditions develop an attachment disorder. Studies undertaken on children from Eastern European orphanages from the mid-1990s showed significantly higher levels of both forms of RAD and of insecure patterns of attachment in the institutionalized children, regardless of how long they had been there. It would appear that children in institutions like these are unable to form selective attachments to their caregivers. The difference between the institutionalized children and the control group had lessened in the follow-up study three years later, although the institutionalized children continued to show significantly higher levels of indiscriminate friendliness. However, even among children raised in the most deprived institutional conditions the majority did not show symptoms of this disorder.

A 2002 study of children in residential nurseries in Bucharest, in which the DAI was used, challenged the current DSM and ICD conceptualizations of disordered attachment and showed that inhibited and disinhibited disorders could coexist in the same child.

There are two studies on the incidence of RAD relating to high risk and maltreated children in the U.S. Both used ICD, DSM and the DAI. The first, in 2004, reported that children from the maltreatment sample were significantly more likely to meet criteria for one or more attachment disorders than children from the other groups, however this was mainly the proposed new classification of disrupted attachment disorder rather than the DSM or ICD classified RAD or DAD. The second study, also in 2004, attempted to ascertain the prevalence of RAD and whether it could be reliably identified in "maltreated" rather than "neglected" toddlers. Of the 94 maltreated toddlers in foster care, 35% were identified as having ICD RAD and 22% as having ICD DAD, and 38% fulfilled the DSM criteria for RAD. This study found that RAD could be reliably identified and also that the inhibited and disinhibited forms were not independent. However, there are some methodological concerns with this study. A number of the children identified as fulfilling the criteria for RAD did in fact have a preferred attachment figure.

It has been suggested by some within the field of attachment therapy that RAD may be quite prevalent because severe child maltreatment, which is known to increase risk for RAD, is prevalent and because children who are severely abused may exhibit behaviors similar to RAD behaviors. The APSAC Taskforce consider this inference to be flawed and questionable. Severely abused children may exhibit similar behaviors to RAD behaviors but there are several far more common and demonstrably treatable diagnoses which may better account for these difficulties. Further, many children experience severe maltreatment and do not develop clinical disorders. Resilience is a common and normal human characteristic. RAD does not underlie all or even most of the behavioral and emotional problems seen in foster children, adoptive children, or children who are maltreated and rates of child abuse and/or neglect or problem behaviors are not a benchmark for estimates of RAD.

There are few data on comorbid conditions, but there are some conditions that arise in the same circumstances in which RAD arises, such as institutionalization or maltreatment. These are principally developmental delays and language disorders associated with neglect. Conduct disorders, oppositional defiant disorder, anxiety disorders, post-traumatic stress disorder and social phobia share many symptoms and are often comorbid with or confused with RAD. Attachment disorder behaviors amongst institutionalized children are correlated with attentional and conduct problems and cognitive levels but nonetheless appear to index a distinct set of symptoms and behaviors.

Attachment disorder is a broad term intended to describe disorders of mood, behavior, and social relationships arising from a failure to form normal attachments to primary care giving figures in early childhood. Such a failure would result from unusual early experiences of neglect, abuse, abrupt separation from caregivers between 6 months and three years of age, frequent change or excessive numbers of caregivers, or lack of caregiver responsiveness to child communicative efforts resulting in a lack of basic trust. A problematic history of social relationships occurring after about age three may be distressing to a child, but does not result in attachment disorder.

The term attachment disorder is used to describe emotional and behavioral problems of young children, and also applied to school-age children, teenagers and adults. The specific difficulties implied depend on the age of the individual being assessed, and a child's attachment-related behaviors may be very different with one familiar adult than with another, suggesting that the disorder is within the relationship and interactions of the two people rather than an aspect of one or the other personality. No list of symptoms can legitimately be presented but generally the term attachment disorder refers to the absence or distortion of age appropriate social behaviors with adults. For example, in a toddler, attachment-disordered behavior could include a failure to stay near familiar adults in a strange environment or to be comforted by contact with a familiar person, whereas in a six-year-old attachment-disordered behavior might involve excessive friendliness and inappropriate approaches to strangers.

There are currently two main areas of theory and practice relating to the definition and diagnosis of attachment disorder, and considerable discussion about a broader definition altogether. The first main area is based on scientific enquiry, is found in academic journals and books and pays close attention to attachment theory. It is described in ICD-10 as reactive attachment disorder, or "RAD" for the inhibited form, and disinhibited attachment disorder, or "DAD" for the disinhibited form. In DSM-IV-TR both comparable inhibited and disinhibited types are called reactive attachment disorder or "RAD".

The second area is controversial and considered pseudoscientific. It is found in clinical practice, on websites and in books and publications, but has little or no evidence base. It makes controversial claims relating to a basis in attachment theory. The use of these controversial diagnoses of attachment disorder is linked to the use of pseudoscientific attachment therapies to treat them.

Some authors have suggested that attachment, as an aspect of emotional development, is better assessed along a spectrum than considered to fall into two non-overlapping categories. This spectrum would have at one end the characteristics called secure attachment; midway along the range of disturbance would be insecure or other undesirable attachment styles; at the other extreme would be

non-attachment. Agreement has not yet been reached with respect to diagnostic criteria.

Finally, the term is also sometimes used to cover difficulties arising in relation to various attachment styles which may not be disorders in the clinical sense.

One study has reported a connection between a specific genetic marker and disorganized attachment (not RAD) associated with problems of parenting. Another author has compared atypical social behavior in genetic conditions such as Williams syndrome with behaviors symptomatic of RAD.

Typical attachment development begins with unlearned infant reactions to social signals from caregivers. The ability to send and receive social communications through facial expressions, gestures and voice develops with social experience by seven to nine months. This makes it possible for an infant to interpret messages of calm or alarm from face or voice. At about eight months, infants typically begin to respond with fear to unfamiliar or startling situations, and to look to the faces of familiar caregivers for information that either justifies or soothes their fear. This developmental combination of social skills and the emergence of fear reactions results in attachment behavior such as proximity-seeking, if a familiar, sensitive, responsive, and cooperative adult is available. Further developments in attachment, such as negotiation of separation in the toddler and preschool period, depend on factors such as the caregiver's interaction style and ability to understand the child's emotional communications.

With insensitive or unresponsive caregivers, or frequent changes, an infant may have few experiences that encourage proximity seeking to a familiar person. An infant who experiences fear but who cannot find comforting information in an adult's face and voice may develop atypical ways of coping with fearfulness such as the maintenance of distance from adults, or the seeking of proximity to all adults. These symptoms accord with the DSM criteria for reactive attachment disorder. Either of these behavior patterns may create a developmental trajectory leading ever farther from typical attachment processes such as the development of an internal working model of social relationships that facilitates both the giving and the receiving of care from others.

Atypical development of fearfulness, with a constitutional tendency either to excessive or inadequate fear reactions, might be necessary before an infant is vulnerable to the effects of poor attachment experiences.

Alternatively, the two variations of RAD may develop from the same inability to develop "stranger-wariness" due to inadequate care. Appropriate fear responses may only be able to develop after an infant has first begun to form a selective attachment. An infant who is not in a position to do this cannot afford not to show interest in any person as they may be potential attachment figures. Faced with a swift succession of carers the child may have no opportunity to form a selective attachment until the possible biologically-determined sensitive period for developing stranger-wariness has passed. It is thought this process may lead to the disinhibited form.

In the inhibited form infants behave as if their attachment system has been "switched off". However the innate capacity for attachment behavior cannot be lost. This may explain why children diagnosed with the inhibited form of RAD from institutions almost invariably go on to show formation of attachment behavior to good carers. However children who suffer the inhibited form as a consequence of neglect and frequent changes of caregiver continue to show the inhibited form for far longer when placed in families.

Additionally, the development of Theory of Mind "may" play a role in emotional development. Theory of Mind is the ability to know that the experience of knowledge and intention lies behind human actions such as facial expressions. Although it is reported that very young infants have different responses to humans than to non-human objects, Theory of Mind develops relatively gradually and possibly results from predictable interactions with adults. However, some ability of this kind must be in place before mutual communication through gaze or other gesture can occur, as it does by seven to nine months. Some neurodevelopmental disorders, such as autism, have been attributed to the absence of the mental functions that underlie Theory of Mind. It is possible that the congenital absence of this ability, or the lack of experiences with caregivers who communicate in a predictable fashion, could underlie the development of reactive attachment disorder.

In Chinese alchemy, elixir poisoning refers to the toxic effects from elixirs of immortality that contained metals and minerals such as mercury and arsenic. The official "Twenty-Four Histories" record numerous Chinese emperors, nobles, and officials who ironically died from taking elixirs in order to prolong their lifespans. The first emperor to die from elixir poisoning was likely Qin Shi Huang (d. 210 BCE) and the last was Yongzheng (d. 1735). Despite common knowledge that immortality potions could be deadly, fangshi and Daoist alchemists continued the elixir-making practice for two millennia.

The distinction between Hua () and Yi (), also known as Sino–barbarian dichotomy, is an ancient Chinese concept that differentiated a culturally defined "China" (called Hua, Huaxia 華夏, or Xia 夏) from cultural or ethnic outsiders (Yi "barbarians"). Although Yi is often translated as "barbarian", other translations of this term in English include "foreigners",

"ordinary others" "wild tribes", and "uncivilized tribes."

The Hua–Yi distinction asserted Chinese superiority, but implied that outsiders could become "Hua" by adopting Chinese values and customs.

Needham and Lu's third justification for taking poisonous elixirs is a drug-induced "temporary death", possibly a trance or coma. In the classic legend (above) about Wei Boyang drinking an elixir of immortality, he appears to die, subsequently revives, and takes more elixir to achieve immortality.

The "Baopuzi" describes a Five Mineral-based multicolored Ninefold Radiance Elixir that can bring a corpse back to life: "If you wish to raise a body that has not been dead for fully three days, bathe the corpse with a solution of one spatula of the blue elixir, open its mouth, and insert another spatula full; it will revive immediately." (tr. Ware 1966:82).

A Tang Daoist text prescribes taking an elixir in doses half the size of a millet grain, but adds, "If one is sincerely determined, and dares to take a whole spatula-full all at once, one will temporarily die ["zànsǐ" 暫死] for half a day or so, and then be restored to life like someone waking from sleep. This however is perilous in the extreme." (tr. Needham and Lu 1974: 295).

Concerns over legitimacy were not limited to the Song alone: states rose up again in the Yuan dynasty, as its rulers were non-Han Chinese. However, the Yuan dynasty adopted a different approach to quelling the conflict. The Yuan asserted that the Song, Liao and Jin were all legitimate; therefore all three dynasties were given their own history, as recognition of their legitimacy.

Despite this, the Yuan racially segregated their people; dividing society into four categories:

- Mongols (蒙古): the ruling group and hence, the most important

- Semu (色目; "assorted categories"): a term for non-Chinese and non-Mongol foreigners who occupied the second slate;

- Han (漢人): a term for the Han Chinese, Jurchens, and Khitan under the rule of the Jin dynasty;

- Southerner (南人): a term for Han Chinese under the rule of the Song dynasty.

In addition, the Yuan also divided society into 10 castes, based on "desirability":

- High officials (大官)

- Minor officials (小官)

- Buddhist monks (釋)

- Daoist priests (道)

- Physicians (医)

- Peasants (農)

- Hunters (獵)

- Courtesans (妓)

- Confucian scholars (儒)

- Beggars (丐)

The Yuan rulers were Mongols and were viewed as barbaric and humiliating for the Han Chinese, although they did not last long in China (from 1271 to 1368).