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.

The AACAP guidelines state that children with reactive attachment disorder are presumed to have grossly disturbed internal models for relating to others. However, the course of RAD is not well studied and there have been few efforts to examine symptom patterns over time. The few existing longitudinal studies (dealing with developmental change with age over a period of time) involve only children from poorly run Eastern European institutions.

Findings from the studies of children from Eastern European orphanages indicate that persistence of the inhibited pattern of RAD is rare in children adopted out of institutions into normative care-giving environments. However, there is a close association between duration of deprivation and severity of attachment disorder behaviors. The quality of attachments that these children form with subsequent care-givers may be compromised, but they probably no longer meet criteria for inhibited RAD. The same group of studies suggests that a minority of adopted, institutionalized children exhibit persistent indiscriminate sociability even after more normative caregiving environments are provided. Indiscriminate sociability may persist for years, even among children who subsequently exhibit preferred attachment to their new caregivers. Some exhibit hyperactivity and attention problems as well as difficulties in peer relationships. In the only longitudinal study that has followed children with indiscriminate behavior into adolescence, these children were significantly more likely to exhibit poor peer relationships.

Studies of children who were reared in institutions have suggested that they are inattentive and overactive, no matter what quality of care they received. In one investigation, some institution-reared boys were reported to be inattentive, overactive, and markedly unselective in their social relationships, while girls, foster-reared children, and some institution-reared children were not. It is not yet clear whether these behaviors should be considered as part of disordered attachment.

There is one case study on maltreated twins published in 1999 with a follow-up in 2006. This study assessed the twins between the ages of 19 and 36 months, during which time they suffered multiple moves and placements. The paper explores the similarities, differences and comorbidity of RAD, disorganized attachment and post traumatic stress disorder. The girl showed signs of the inhibited form of RAD while the boy showed signs of the indiscriminate form. It was noted that the diagnosis of RAD ameliorated with better care but symptoms of post traumatic stress disorder and signs of disorganized attachment came and went as the infants progressed through multiple placement changes. At age three, some lasting relationship disturbance was evident.

In the follow-up case study when the twins were aged three and eight years, the lack of longitudinal research on maltreated as opposed to institutionalized children was again highlighted. The girl's symptoms of disorganized attachment had developed into controlling behaviors—a well-documented outcome. The boy still exhibited self-endangering behaviors, not within RAD criteria but possibly within "secure base distortion", (where the child has a preferred familiar caregiver, but the relationship is such that the child cannot use the adult for safety while gradually exploring the environment). At age eight the children were assessed with a variety of measures including those designed to access representational systems, or the child's "internal working models". The twins' symptoms were indicative of different trajectories. The girl showed externalizing symptoms (particularly deceit), contradictory reports of current functioning, chaotic personal narratives, struggles with friendships, and emotional disengagement with her caregiver, resulting in a clinical picture described as "quite concerning". The boy still evidenced self-endangering behaviors as well as avoidance in relationships and emotional expression, separation anxiety and impulsivity and attention difficulties. It was apparent that life stressors had impacted each child differently. The narrative measures used were considered helpful in tracking how early attachment disruption is associated with later expectations about relationships.

One paper using questionnaires found that children aged three to six, diagnosed with RAD, scored lower on empathy but higher on self-monitoring (regulating your behavior to "look good"). These differences were especially pronounced based on ratings by parents, and suggested that children with RAD may systematically report their personality traits in overly positive ways. Their scores also indicated considerably more behavioral problems than scores of the control children.

ODD has an estimated lifetime prevalence of 10.2% (11.2% for males, 9.2% for females).

Negative parenting practices and parent–child conflict may lead to antisocial behavior, but they may also be a reaction to the oppositional and aggressive behaviors of children. Factors such as a family history of mental illnesses and/or substance abuse as well as a dysfunctional family and inconsistent discipline by a parent or guardian can lead to the development of behavior disorders.

Insecure parent–child attachments can also contribute to ODD. Often little internalization of parent and societal standards exists in children with conduct problems. These weak bonds with their parents may lead children to associate with delinquency and substance abuse.

Family instability and stress can also contribute to the development of ODD. Although the association between family factors and conduct problems is well established, the nature of this association and the possible causal role of family factors continues to be debated.

Low socioeconomic status is associated with poor parenting, specifically with inconsistent discipline and poor parental monitoring, which are then associated with an early onset of aggression and antisocial behaviors.

Externalizing problems are reported to be more frequent among minority-status youth, a finding that is likely related to economic hardship, limited employment opportunities, and living in high-risk urban neighborhoods.

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.

The majority of 1-year-old children can tolerate brief separations from familiar caregivers and are quickly comforted when the caregivers return. These children also use familiar people as a "secure base" and return to them periodically when exploring a new situation. Such children are said to have a secure attachment style, and characteristically continue to develop well both cognitively and emotionally.

Smaller numbers of children show less positive development at age 12 months. Their less desirable attachment styles may be predictors of poor later social development. Although these children's behavior at 12 months is not a serious problem, they appear to be on developmental trajectories that will end in poor social skills and relationships. Because attachment styles may serve as predictors of later development, it may be appropriate to think of certain attachment styles as part of the range of attachment disorders.

Insecure attachment styles in toddlers involve unusual reunions after separation from a familiar person. The children may snub the returning caregiver, or may go to the person but then resist being picked up. They may reunite with the caregiver, but then persistently cling to him/her, and fail to return to their previous play. These children are more likely to have later social problems with peers and teachers, but some of them spontaneously develop better ways of interacting with other people.

A small group of toddlers show a distressing way of reuniting after a separation. Called a disorganized/disoriented style, this reunion pattern can involve looking dazed or frightened, freezing in place, backing toward the caregiver or approaching with head sharply averted, or showing other behaviors that seem to imply fearfulness of the person who is being sought. Disorganized attachment has been considered a major risk factor for child psychopathology, as it appears to interfere with regulation or tolerance of negative emotions and may thus foster aggressive behavior. Disorganized patterns of attachment have the strongest links to concurrent and subsequent psychopathology, and considerable research has demonstrated both within-the-child and environmental correlates of disorganized attachment.

Disinhibited attachment disorder of childhood (DAD) according to the International Classification of Diseases (ICD-10), is defined as:

Disinhibited attachment disorder is a subtype of the ICD-10 category F94, "Disorders of social functioning with onset specific to childhood and adolescence". The other subtype of F94 is reactive attachment disorder of childhood (RAD – F94 .1).

Synonymous or similar disorders include Affectionless psychopathy and Institutional syndrome.

Within the ICD-10 category scheme, disinhibited attachment disorder specifically excludes Asperger syndrome (F84.5), hospitalism in children (F43.2), and hyperkinetic disorders (F90.-).

The DSM-IV distinguishes two categories of RAD: an inhibited subtype and a disinhibited subtype (in the DSM it is listed as 313.89 under infant diagnoses). The ICD-10 describes the former, emotionally withdrawn subtype as RAD and the latter subtype as Disinhibited Attachment Disorder (DAD) (Zeanah "et al.", 2004).

Generally, the DSM-IV criteria for the inhibited subtype of RAD were generated by studies done on children who were maltreated or abused. Criteria for the DSM-IV disinhibited subtype of RAD were based on research on children raised in institutions (Zeanah, 1996). This is largely based on the fact that inhibited subtype of RAD is more prevalent in maltreated children, and the disinhibited subtype of RAD is more prevalent in children raised in institutions (Zeanah, 2000).

The only certain way to prevent FAS is to avoid drinking alcohol during pregnancy. In the United States, the Surgeon General recommended in 1981, and again in 2005, that women abstain from alcohol use while pregnant or while planning a pregnancy, the latter to avoid damage even in the earliest stages (even weeks) of a pregnancy, as the woman may not be aware that she has conceived. In the United States, federal legislation has required that warning labels be placed on all alcoholic beverage containers since 1988 under the Alcoholic Beverage Labeling Act.

There is some controversy surrounding the "zero-tolerance" approach taken by many countries when it comes to alcohol consumption during pregnancy. The assertion that moderate drinking causes FAS is said to lack strong evidence and, in fact, the practice of equating a responsible level of drinking with potential harm to the fetus may have negative social, legal, and health impacts. In addition, special care should be taken when considering statistics on this disease, as prevalence and causation is often linked with FASD, which is more common and causes less harm, as opposed to FAS.

The secondary disabilities of FAS are those that arise later in life secondary to CNS damage. These disabilities often emerge over time due to a mismatch between the primary disabilities and environmental expectations; secondary disabilities can be ameliorated with early interventions and appropriate supportive services.

Six main secondary disabilities were identified in a University of Washington research study of 473 subjects diagnosed with FAS, PFAS (partial fetal alcohol syndrome), and ARND (alcohol-related neurodevelopmental disorder):

- Mental health problems: Diagnosed with ADHD, Clinical Depression, or other mental illness, experienced by over 90% of the subjects

- Disrupted school experience: Suspended or expelled from school or dropped out of school, experienced by 60% of the subjects (age 12 and older)

- Trouble with the law: Charged or convicted with a crime, experienced by 60% of the subjects (age 12 and older)

- Confinement: For inpatient psychiatric care, inpatient chemical dependency care, or incarcerated for a crime, experienced by about 50% of the subjects (age 12 and older)

- Inappropriate sexual behavior: Sexual advances, sexual touching, or promiscuity, experienced by about 50% of the subjects (age 12 and older)

- Alcohol and drug problems: Abuse or dependency, experienced by 35% of the subjects (age 12 and older)

Two additional secondary disabilities exist for adults:

- Dependent living: Group home, living with family or friends, or some sort of assisted living, experienced by 80% of the subjects (age 21 and older)

- Problems with employment: Required ongoing job training or coaching, could not keep a job, unemployed, experienced by 80% of the subjects (age 21 and older)

According to the linear no-threshold model, any exposure to ionizing radiation, even at doses too low to produce any symptoms of radiation sickness, can induce cancer due to cellular and genetic damage. Under the assumption, survivors of acute radiation syndrome face an increased risk of developing cancer later in life. The probability of developing cancer is a linear function with respect to the effective radiation dose. In radiation-induced cancer, the speed at which the condition advances, the prognosis, the degree of pain, and every other feature of the disease are not believed to be functions of the radiation dosage.

However, some studies contradict the linear no-threshold model. These studies indicate that some low levels of radiation do not increase cancer risk at all, and that there may exist a threshold dosage of ionizing radiation below which exposure should be considered safe. Nonetheless the 'no safe amount' assumption is the basis of US and most national regulatory policies regarding "man-made" sources of radiation.

There are two major databases that track radiation accidents: The American ORISE REAC/TS and the European IRSN ACCIRAD. REAC/TS shows 417 accidents occurring between 1944 and 2000, causing about 3000 cases of acute radiation syndrome, of which 127 were fatal. ACCIRAD lists 580 accidents with 180 ARS fatalities for an almost identical period. The two deliberate bombings are not included in either database, nor are any possible radiation-induced cancers from low doses. The detailed accounting is difficult because of confounding factors. ARS may be accompanied by conventional injuries such as steam burns, or may occur in someone with a pre-existing condition undergoing radiotherapy. There may be multiple causes for death, and the contribution from radiation may be unclear. Some documents may incorrectly refer to radiation-induced cancers as radiation poisoning, or may count all overexposed individuals as survivors without mentioning if they had any symptoms of ARS. The table below attempts to catalog some cases of ARS. Many of these incidents involved additional fatalities from other causes, such as cancer, which are excluded from this table.

Although the disease is more common in African-Americans than in Caucasians, it may occur in any patient population.

Therapies that support reverse remodeling have been investigated, and this may suggests a new approach to the prognosis of cardiomyopathies (see ventricular remodeling).

The term alimentary mycotoxicoses refers to the effect of poisoning by Mycotoxins (The term 'mycotoxin' is usually reserved for the toxic chemical products produced by fungi that readily colonize crops) through food consumption. Mycotoxins sometimes have important effects on human and animal health. For example, an outbreak which occurred in the UK in 1960 caused the death of 100,000 turkeys which had consumed aflatoxin-contaminated peanut meal. In the USSR in World War II, 5,000 people died due to Alimentary Toxic Aleukia (ALA). The common foodborne Mycotoxins include:

- Aflatoxins – originated from Aspergillus parasiticus and Aspergillus flavus. They are frequently found in tree nuts, peanuts, maize, sorghum and other oilseeds, including corn and cottonseeds. The pronounced forms of Aflatoxins are those of B1, B2, G1, and G2, amongst which Aflatoxin B1 predominantly targets the liver, which will result in necrosis, cirrhosis, and carcinoma. In the US, the acceptable level of total aflatoxins in foods is less than 20 μg/kg, except for Aflatoxin M1 in milk, which should be less than 0.5 μg/kg. The official document can be found at FDA's website.

- Altertoxins – are those of Alternariol (AOH), Alternariol methyl ether (AME), Altenuene (ALT), Altertoxin-1 (ATX-1), Tenuazonic acid (TeA) and Radicinin (RAD), originated from Alternaria spp. Some of the toxins can be present in sorghum, ragi, wheat and tomatoes. Some research has shown that the toxins can be easily cross-contaminated between grain commodities, suggesting that manufacturing and storage of grain commodities is a critical practice.

- Citrinin

- Citreoviridin

- Cyclopiazonic acid

- Cytochalasins

- Ergot alkaloids / Ergopeptine alkaloids – Ergotamine

- Fumonisins – Crop corn can be easily contaminated by the fungi Fusarium moniliforme, and its Fumonisin B1 will cause Leukoencephalomalacia (LEM) in horses, Pulmonary edema syndrome (PES) in pigs, liver cancer in rats and Esophageal cancer in humans. For human and animal health, both the FDA and the EC have regulated the content levels of toxins in food and animal feed.

- Fusaric acid

- Fusarochromanone

- Kojic acid

- Lolitrem alkaloids

- Moniliformin

- 3-Nitropropionic acid

- Nivalenol

- Ochratoxins – In Australia, The Limit of Reporting (LOR) level for Ochratoxin A (OTA) analyses in 20th Australian Total Diet Survey was 1 µg/kg, whereas the EC restricts the content of OTA to 5 µg/kg in cereal commodities, 3 µg/kg in processed products and 10 µg/kg in dried vine fruits.

- Oosporeine

- Patulin – Currently, this toxin has been advisably regulated on fruit products. The EC and the FDA have limited it to under 50 µg/kg for fruit juice and fruit nectar, while limits of 25 µg/kg for solid-contained fruit products and 10 µg/kg for baby foods were specified by the EC.

- Phomopsins

- Sporidesmin A

- Sterigmatocystin

- Tremorgenic mycotoxins – Five of them have been reported to be associated with molds found in fermented meats. These are Fumitremorgen B, Paxilline, Penitrem A, Verrucosidin, and Verruculogen.

- Trichothecenes – sourced from Cephalosporium, Fusarium, Myrothecium, Stachybotrys and Trichoderma. The toxins are usually found in molded maize, wheat, corn, peanuts and rice, or animal feed of hay and straw. Four trichothecenes, T-2 toxin, HT-2 toxin, diacetoxyscirpenol (DAS) and deoxynivalenol (DON) have been most commonly encountered by humans and animals. The consequences of oral intake of, or dermal exposure to, the toxins will result in Alimentary toxic aleukia, neutropenia, aplastic anemia, thrombocytopenia and/or skin irritation. In 1993, the FDA issued a document for the content limits of DON in food and animal feed at an advisory level. In 2003, US published a patent that is very promising for farmers to produce a trichothecene-resistant crop.

- Zearalenone

- Zearalenols

Viral infections make up perhaps one third of cases of food poisoning in developed countries. In the US, more than 50% of cases are viral and noroviruses are the most common foodborne illness, causing 57% of outbreaks in 2004. Foodborne viral infection are usually of intermediate (1–3 days) incubation period, causing illnesses which are self-limited in otherwise healthy individuals; they are similar to the bacterial forms described above.

- Enterovirus

- Hepatitis A is distinguished from other viral causes by its prolonged (2–6 week) incubation period and its ability to spread beyond the stomach and intestines into the liver. It often results in jaundice, or yellowing of the skin, but rarely leads to chronic liver dysfunction. The virus has been found to cause infection due to the consumption of fresh-cut produce which has fecal contamination.

- Hepatitis E

- Norovirus

- Rotavirus