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.

Perfectionism, in psychology, is a personality trait characterized by a person's striving for flawlessness and setting high performance standards, accompanied by critical self-evaluations and concerns regarding others' evaluations. It is best conceptualized as a multidimensional characteristic, as psychologists agree that there are many positive and negative aspects. In its maladaptive form, perfectionism drives people to attempt to achieve an unattainable ideal, while their adaptive perfectionism can sometimes motivate them to reach their goals. In the end, they derive pleasure from doing so. When perfectionists do not reach their goals, they often fall into depression.

Perfectionists strain compulsively and unceasingly toward unobtainable goals, and measure their self-worth by productivity and accomplishment. Pressuring oneself to achieve unrealistic goals inevitably sets the person up for disappointment. Perfectionists tend to be harsh critics of themselves when they fail to meet their standards.

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.

In medicine a broad definition of syndrome is used, which describes a collection of symptoms and findings without necessarily tying them to a single identifiable pathogenesis. The more specific definition employed in medical genetics describes a subset of all medical syndromes.

Klüver–Bucy syndrome is a syndrome resulting from bilateral lesions of the medial temporal lobe (including amygdaloid nucleus). Klüver–Bucy syndrome may present with compulsive eating, hypersexuality, insertion of inappropriate objects in the mouth (hyperorality), visual agnosia, and .

Tardive Dysmentia is a rarely used term introduced in a 1983 paper to describe "changes in affect, activation level, and interpersonal interaction", and hypothesized to be caused by long-term exposure to neuroleptic drugs in the same way as the much better known syndrome of tardive dyskinesia. Several papers in the following years discussed the validity of the concept, and this small literature was reviewed in a 1993 publication by M. S. Myslobodsky, who drew attention to the "possibility that the syndrome of dysmentia is occasional excessive emotional reactivity, enhanced responsiveness to environmental stimuli, and indifference to or reduced awareness of the patient's abnormal involuntary movements", but concluded that the pathophysiology is uncertain. Since then, the term has fallen into disuse, receiving at most only passing mentions in the literature.

A syndrome is a set of medical signs and symptoms occurring together, constitutes a particular disease or disorder. The word derives from the Greek σύνδρομον, meaning "concurrence". In some instances, a syndrome is so closely linked with a pathogenesis or cause that the words "syndrome", "disease", and "disorder" end up being used interchangeably for them. This is especially true of inherited syndromes. For example, Down syndrome, Wolf–Hirschhorn syndrome, and Andersen syndrome are disorders with known pathogeneses, so each is more than just a set of signs and symptoms, despite the "syndrome" nomenclature. In other instances, a syndrome is not specific to only one disease. For example, toxic shock syndrome can be caused by various toxins; premotor syndrome can be caused by various brain lesions; and premenstrual syndrome is not a disease but simply a set of symptoms.

If an underlying genetic cause is suspected but not known, a condition may be referred to as a genetic association (often just "association" in context). By definition, an association indicates that the collection of signs and symptoms occurs in combination more frequently than would be likely by chance alone.

Syndromes are often named after the physician or group of physicians that discovered them or initially described the full clinical picture. Such eponymous syndrome names are examples of medical eponyms. Recently, there has been a shift towards naming conditions descriptively (by symptoms or underlying cause) rather than eponymously, but the eponymous syndrome names often persist in common usage.

Klüver–Bucy syndrome was first documented among certain humans who had experienced temporal lobectomy in 1955 by H. Terzian and G.D. Ore. It was first noted in a human with meningoencephalitis in 1975 by Marlowe et al. Klüver–Bucy syndrome can manifest after either of these (lobectomies can be medically required by such reasons as accidents or tumors), but may also appear in humans with acute herpes simplex encephalitis or following a stroke. Other conditions may also contribute to a diagnosis of Klüver–Bucy syndrome, including Pick Disease, Alzheimer's Disease, ischemia, anoxia, progressive subcortical gliosis, Rett syndrome, porphyria and carbon monoxide poisoning, among others.

It is rare for humans to manifest all of the identified symptoms of the syndrome; three or more are required for diagnosis. Among humans, the most common symptoms include placidity, hyperorality and dietary changes. They may also present with an inability to recognize objects or inability to recognize faces or other memory disorders. Social neurosciences research shows that changes in temporal lobe is identified as a cause for aberrant sexual and hyper-sexual behaviors.

Multisystem developmental disorder (MSDD) is a term used by Stanley Greenspan to describe children under age 3 who exhibit signs of impaired communication as in autism, but with strong emotional attachments atypical of autism. It is described in the DC:0-3R manual as an optional diagnosis for children under two years of age.

The term dysphrenia was coined by the German medical specialist Karl Kahlbaum to designate a clinical picture in 19th-century psychiatry. Today the concept is still used in the western world as a lay generic synonym for mental disorder in adults, and as a term to describe different cognitive/verbal/behavioral deficits in children and adolescents. It is also used in the People's Republic of China, controversially, to identify a local medical diagnostic category. A number of followers of the Falun Gong cult and other social movements considered insurrectionary by the regime are said to have been diagnosed with dysphrenia.

The medical expression tardive dysphrenia was first proposed by the American neurologist Stanley Fahn and collaborators in the 1970s. It was originally linked to a unique and rare non-motor behavioral/mental neuroleptic drug-induced tardive syndrome observed in psychiatric patients—schizophrenia in particular—who had been treated with typical antipsychotics.

Tardive dysphrenia was conceived to precede tardive dyskinesia and the other already-known neuroleptic-induced tardive syndromes (tardive dystonia, tardive akathisia). More recently, the Brazilian psychiatrist Leopoldo Hugo Frota extended Fahn's original construct to encompass the independently described but etiologically related concepts of rebound psychosis, supersensitivity psychosis (Guy Chouinard), and schizophrenia pseudo-refractoriness (Heinz Lehmann & Thomas Ban) or secondary acquired refractoriness.

It is estimated that up to 16.5% of elementary school aged children present elevated SOR behaviors in the tactile or auditory modalities. However, this figure might represent an underestimation of Sensory Over Responsivity prevalence, since this study did not include children with developmental disorders or those delivered preterm, who are more likely to present it.

This figure is, nonetheless, larger than what previous studies with smaller samples had shown: an estimate of 5–13% of elementary school aged children.

Incidence for the remaining subtypes is currently unknown.

The term "multisystem developmental disorder" has also been used to describe various developmental disorders. These include:

- Alagille syndrome, an autosomal dominant disorder with a wide range of features and manifestations. Its five most significant features are chronic cholestasis, a condition where bile cannot flow from the liver to the duodenum, occurring in 95% of cases; heart abnormalities (over 90%); butterfly vertebrae; posterior embryotoxon and a distinctive face (prominent forehead, deep-set eyes, and a pointed chin).

- Rubinstein-Taybi syndrome, a mental retardation syndrome characterized by broad thumbs, facial abnormalities, and big toes alongside mental retardation.

- Williams syndrome, a neurodevelopmental disorder characterized by a unique profile of strengths and deficits; most with the condition have mild mental retardation but have grammatical and lexical abilities above what would be expected from their IQs. They are hypersocial and empathetic, but social isolation is commonly experienced.

- Proteus syndrome, a congenital disorder causing disproportionate growth of skin, bone, and other tissues.

- Asphyxiating thoracic dysplasia, a autosomal recessive skeletal disorder with an estimated prevalence of between 1 in 100,000 and 1 in 130,000 live births.

Because comorbid conditions are common with sensory integration issues, a person may have other conditions as well. People who receive the diagnosis of sensory processing disorder may also have signs of anxiety problems, ADHD, food intolerances, behavioral disorders and other disorders.

A 2007 study found that 78% of a clinical sample of OCD patients had intrusive images. Most people who suffer from intrusive thoughts have not identified themselves as having OCD, because they may not have what they believe to be classic symptoms of OCD, such as handwashing. Yet, epidemiological studies suggest that intrusive thoughts are the most common kind of OCD worldwide; if people in the United States with intrusive thoughts gathered, they would form the fourth-largest city in the US, following New York City, Los Angeles, and Chicago.

The prevalence of OCD in every culture studied is at least 2% of the population, and the majority of those have obsessions, or bad thoughts, only; this results in a conservative estimate of more than 2 million sufferers in the United States alone (as of 2000). One author estimates that one in 50 adults have OCD and about 10–20% of these have sexual obsessions. A recent study found that 25% of 293 patients with a primary diagnosis of OCD had a history of sexual obsessions.

An intrusive thought is an unwelcome involuntary thought, image, or unpleasant idea that may become an obsession, is upsetting or distressing, and can feel difficult to manage or eliminate. When such thoughts are associated with obsessive-compulsive disorder (OCD), depression, body dysmorphic disorder (BDD), and sometimes attention-deficit hyperactivity disorder (ADHD), the thoughts may become paralyzing, anxiety-provoking, or persistent. Intrusive thoughts may also be associated with episodic memory, unwanted worries or memories from OCD, posttraumatic stress disorder, other anxiety disorders, eating disorders, or psychosis. Intrusive thoughts, urges, and images are of inappropriate things at inappropriate times, and generally have aggressive, sexual, or blasphemous themes.

A systematic review described improvement and occupational outcomes of people with CFS found that "the median full recovery rate was 5% (range 0–31%) and the median proportion of patients who improved during follow-up was 39.5% (range 8–63%). Return to work at follow-up ranged from 8 to 30% in the three studies that considered this outcome." ... "In five studies, a worsening of symptoms during the period of follow-up was reported in between 5 and 20% of patients." A good outcome was associated with less fatigue severity at baseline. Other factors were occasionally, but not consistently, related to outcome, including age at onset (5 of 16 studies), and attributing illness to a psychological cause and/or having a sense of control over symptoms (4 of 16 studies). Another review found that children have a better prognosis than adults, with 54–94% having recovered by follow-up compared to less than 10% of adults returning to pre-illness levels of functioning.

Tension myositis syndrome (TMS), also known as tension myoneural syndrome or mindbody syndrome is a name given by John E. Sarno to a condition he describes as characterized by musculoskeletal and nerve symptoms, most notably back pain. Sarno, a Professor of Clinical Rehabilitation Medicine at New York University School of Medicine and Attending Physician at The Rusk Institute of Rehabilitation Medicine at New York University Medical Center, has described TMS in four books, and has stated that the condition may be involved in other pain disorders as well. The treatment protocol for TMS includes education, writing about emotional issues, resumption of a normal lifestyle and, for some patients, support meetings and/or psychotherapy. In 2007, David Schechter (a medical doctor and former student and research assistant of Sarno's) published a peer-reviewed study of TMS treatment showing a 54% success rate for chronic back pain. In terms of statistical significance and success rate, the study outperformed similar studies of other psychological interventions for chronic back pain.

The TMS diagnosis and treatment protocol are not accepted by the mainstream medical community. However, TMS and Sarno's treatment methods have received national attention, including a segment on ABC's "20/20"; an episode of "Larry King Live"; an interview with "Medscape"; and articles in "Newsweek", "The Seattle Times", and "The New York Times". Prominent medical doctors who support TMS treatment include Andrew Weil and Mehmet Oz. Notable patients treated for tension myositis syndrome include Senator Tom Harkin, John Stossel, Howard Stern, and Anne Bancroft.

All ethnic groups and income levels are susceptible to the illness. The CDC states that CFS is "at least as common" in African Americans and Hispanics as Caucasians. A 2009 meta-analysis, however, showed that compared with the White American majority, African Americans and Native Americans have a higher risk of CFS, though it acknowledged that studies and data were limited. More women than men get CFS — between 60 and 85% of cases are women; however, there is some indication that the prevalence among men is underreported. The illness is reported to occur more frequently in persons between the ages of 40 and 59. CFS is less prevalent among children and adolescents than among adults.

Blood relatives of those who have CFS appear to be more predisposed. There is no direct evidence that CFS is contagious.

Psychological stress, childhood trauma, perfectionist personalities, old age, lower middle education, low physical fitness, preexisting psychological illness, and allergies may be risk factors for developing chronic fatigue syndrome. This has led some to believe that stress-related visceral responses underlie CFS. Pre-existing depressive and anxiety disorders, as well as high expectation of parents and family history were predisposing factors identified in another review.

People with CFS and their relatives tend to attribute their illness to physical causes (such as a virus or pollution) rather than to psychological causes. Such attributions are associated with increased symptoms and impairment, and worse outcomes over time.

Nevo Syndrome is considered to be a rare disorder. Since its first appearance in 1974, only a handful of cases have been reported. Studies have shown showing similarities between Nevo Syndrome with Ehlers-Danlos syndrome as well as Sotos syndrome. There is an astounding overlap of phenotypic manifestations between Nevo Syndrome and the more frequent Sotos syndrome, which are both caused by the NSD1 deletion. Sotos syndrome is an autosomal dominant condition associated with learning disabilities, a distinctive facial appearance, and overgrowth. Studies have shown an overwhelming occurrence (half of those involved in the study) of Nevo syndrome in those individuals of Middle-Eastern descent.

While psychogenic pain and pain disorder are accepted diagnoses in the medical community, the TMS modality is more controversial.

A non-peer-reviewed 2005 study by Schechter at the Seligman Medical Institute (SMI), co-authored with institute director Arthur Smith, found that treatment of TMS achieved a 57% success rate among patients with chronic back pain.

A peer-reviewed 2007 study with Schechter, Smith and Stanley Azen, Professor and Co-Director of Biostatistics in the Department of Preventative Medicine at the USC Keck School of Medicine, found a 54% success rate for treatment of TMS ("P"<.00001). The treatment consisted of office visits, at-home educational materials, writing about emotional issues and psychotherapy. The average pain duration for the study's patients was 9 years. Patients with less than 6 months of back pain were excluded to "control for the confounder that most back pain episodes typically resolve on their own in a few weeks."

Schechter, Smith and Azen also compared their results to the results of three studies of other psychological treatments for chronic back pain. The three non-TMS studies were selected because of (a) their quality, as judged by the Cochrane Collaboration, and (b) the similarity of their pain measurements to those used in the TMS study. Of the three non-TMS studies, only one (the Turner study) showed a statistically significant improvement. Compared to the 2007 TMS study, the Turner study had a lower success rate (26%-35%, depending on the type of psychological treatment) and a lower level of statistical significance ("P"<.05).

Schechter, "et al." state that one advantage of TMS treatment is that it avoids the risks associated with surgery and medication, but they caution that the risks of TMS treatment are somewhat unknown due to the relatively low number of patients studied so far.

Childhood amnesia, also called infantile amnesia, is the inability of adults to retrieve episodic memories which are memories of specific events (times, places, associated emotions, and other contextual who, what, when, and where) before the age of 2–4 years, as well as the period before age 10 of which adults retain fewer memories than might otherwise be expected given the passage of time. The development of a cognitive self is also thought by some to have an effect on encoding and storing early memories. Some research has demonstrated that children can remember events from the age of 1, but that these memories may decline as children get older.

Most psychologists differ in defining the offset of childhood amnesia. Some define it as the age from which a first memory can be retrieved. This is usually at the age of 3 or 4, but it can range from 2 to 8 years. Changes in encoding, storage and retrieval of memories during early childhood are all important when considering childhood amnesia. Some other research shows differences between gender and culture, which is implicated in the development of language. Childhood amnesia is particularly important to consider in regard to false memories and the development of the brain in early years. Proposed explanations of childhood amnesia are Freud's trauma theory, neurological development, development of the cognitive self, emotion and language.

Nevo Syndrome is an autosomal recessive disorder. Most times in which a child is afflicted with Nevo Syndrome, both their parents are of average height and weight. It is only until after birth when the characteristic physical traits associated with disease are manifested, and the disorder is actually diagnosed. One study showed that despite the increased growth rates, the patient was completely healthy up until age 6, when he was admitted into the hospital. Nevo syndrome is usually associated with early childhood fatality. Children with Nevo Syndrome have a high occurrence of death due to cardiac arrest because their developing hearts cannot keep up with their overgrown body.

Foreign language anxiety, or xenoglossophobia, is the feeling of , worry, nervousness and apprehension experienced in learning or using a second or foreign language. The feelings may stem from any second language context whether it is associated with the productive skills of speaking and writing or the receptive skills of reading and listening.

Foreign language anxiety is a form of what psychologists describe as a "specific anxiety reaction". Some individuals are more predisposed to anxiety than others and may feel anxious in a wide variety of situations. Foreign language anxiety, however, is situation-specific and so it can also affect individuals who are not characteristically anxious in other situations.

Around 1 in 1,000 boys are born with a 47,XYY karyotype. The incidence of 47,XYY is not known to be affected by the parents' ages.