There are many physical health factors associated with developmental disabilities. For some specific syndromes and diagnoses, these are inherent, such as poor heart function in people with Down syndrome. People with severe communication difficulties find it difficult to articulate their health needs, and without adequate support and education might not recognize ill health. Epilepsy, sensory problems (such as poor vision and hearing), obesity and poor dental health are over-represented in this population. Life expectancy among people with developmental disabilities as a group is estimated at 20 years below average, although this is improving with advancements in adaptive and medical technologies, and as people are leading healthier, more fulfilling lives, and some conditions (such as Freeman-Sheldon syndrome) do not impact life expectancy.

The causes of developmental disabilities are varied and remain unknown in a large proportion of cases. Even in cases of known etiology the line between "cause" and "effect" is not always clear, leading to difficulty in categorizing causes.

Genetic factors have long been implicated in the causation of developmental disabilities. There is also a large environmental component to these conditions, and the relative contributions of nature versus nurture have been debated for decades.

Current theories on causation focus on genetic factors, and over 1,000 known genetic conditions include developmental disabilities as a symptom.

Developmental disabilities affect between 1 and 2% of the population in most western countries, although many government sources acknowledge that statistics are flawed in this area. The worldwide proportion of people with developmental disabilities is believed to be approximately 1.4%. It is twice as common in males as in females, and some researchers have found that the prevalence of mild developmental disabilities is likely to be higher in areas of poverty and deprivation, and among people of certain ethnicities.

Several prenatal and perinatal complications have been reported as possible risk factors for autism. These risk factors include maternal gestational diabetes, maternal and paternal age over 30, bleeding after first trimester, use of prescription medication (e.g. valproate) during pregnancy, and meconium in the amniotic fluid. While research is not conclusive on the relation of these factors to autism, each of these factors has been identified more frequently in autistic children compared to their non-autistic siblings and other normally developing youth.

Low vitamin D levels in early development has been hypothesized as a risk factor for autism.

Autism spectrum disorders tend to be highly comorbid with other disorders. Comorbidity may increase with age and may worsen the course of youth with ASDs and make intervention/treatment more difficult. Distinguishing between ASDs and other diagnoses can be challenging, because the traits of ASDs often overlap with symptoms of other disorders, and the characteristics of ASDs make traditional diagnostic procedures difficult.

The most common medical condition occurring in individuals with autism spectrum disorders is seizure disorder or epilepsy, which occurs in 11-39% of individuals with ASD. Tuberous sclerosis, a medical condition in which non-malignant tumors grow in the brain and on other vital organs, occurs in 1-4% of individuals with ASDs.

Intellectual disabilities are some of the most common comorbid disorders with ASDs. Recent estimates suggest that 40-69% of individuals with ASD have some degree of an intellectual disability, more likely to be severe for females. A number of genetic syndromes causing intellectual disability may also be comorbid with ASD, including fragile X syndrome, Down syndrome, Prader-Willi and Angelman syndromes, and Williams syndrome.

Learning disabilities are also highly comorbid in individuals with an ASD. Approximately 25-75% of individuals with an ASD also have some degree of a learning disability.

Various anxiety disorders tend to co-occur with autism spectrum disorders, with overall comorbidity rates of 7-84%. Rates of comorbid depression in individuals with an ASD range from 4–58%. The relationship between ASD and schizophrenia remains a controversial subject under continued investigation, and recent meta-analyses have examined genetic, environmental, infectious, and immune risk factors that may be shared between the two conditions.

Deficits in ASD are often linked to behavior problems, such as difficulties following directions, being cooperative, and doing things on other people's terms. Symptoms similar to those of attention deficit hyperactivity disorder (ADHD) can be part of an ASD diagnosis.

Sensory processing disorder is also comorbid with ASD, with comorbidity rates of 42–88%.

Neurodevelopmental disorders are in their multitude associated with widely varying degrees of difficulty, depending on which there are different degrees of mental, emotional, physical, and economic consequences for individuals, and in turn families, groups and society.

Among children, the cause of intellectual disability is unknown for one-third to one-half of cases. About 5% of cases are inherited from a person's parents. Genetic defects that cause intellectual disability but are not inherited can be caused by accidents or mutations in genetic development. Examples of such accidents are development of an extra chromosome 18 (trisomy 18) and Down syndrome, which is the most common genetic cause. Velocariofacial syndrome and fetal alcohol spectrum disorders are the two next most common causes. However, doctors have found many other causes. The most common are:

- Genetic conditions. Sometimes disability is caused by abnormal genes inherited from parents, errors when genes combine, or other reasons. The most prevalent genetic conditions include Down syndrome, Klinefelter syndrome, Fragile X syndrome (common among boys), neurofibromatosis, congenital hypothyroidism, Williams syndrome, phenylketonuria (PKU), and Prader–Willi syndrome. Other genetic conditions include Phelan-McDermid syndrome (22q13del), Mowat–Wilson syndrome, genetic ciliopathy, and Siderius type X-linked intellectual disability () as caused by mutations in the "PHF8" gene (). In the rarest of cases, abnormalities with the X or Y chromosome may also cause disability. 48, XXXX and 49, XXXXX syndrome affect a small number of girls worldwide, while boys may be affected by 49, XXXXY, or 49, XYYYY. 47, XYY is not associated with significantly lowered IQ though affected individuals may have slightly lower IQs than non-affected siblings on average.

- Problems during pregnancy. Intellectual disability can result when the fetus does not develop properly. For example, there may be a problem with the way the fetus' cells divide as it grows. A pregnant person who drinks alcohol (see fetal alcohol spectrum disorder) or gets an infection like rubella during pregnancy may also have a baby with intellectual disability.

- Problems at birth. If a baby has problems during labor and birth, such as not getting enough oxygen, he or she may have developmental disability due to brain damage.

- Exposure to certain types of disease or toxins. Diseases like whooping cough, measles, or meningitis can cause intellectual disability if medical care is delayed or inadequate. Exposure to poisons like lead or mercury may also affect mental ability.

- Iodine deficiency, affecting approximately 2 billion people worldwide, is the leading preventable cause of intellectual disability in areas of the developing world where iodine deficiency is endemic. Iodine deficiency also causes goiter, an enlargement of the thyroid gland. More common than full-fledged cretinism, as intellectual disability caused by severe iodine deficiency is called, is mild impairment of intelligence. Certain areas of the world due to natural deficiency and governmental inaction are severely affected. India is the most outstanding, with 500 million suffering from deficiency, 54 million from goiter, and 2 million from cretinism. Among other nations affected by iodine deficiency, China and Kazakhstan have instituted widespread iodization programs, whereas, as of 2006, Russia had not.

- Malnutrition is a common cause of reduced intelligence in parts of the world affected by famine, such as Ethiopia.

- Absence of the arcuate fasciculus.

Intellectual disability affects about 2–3% of the general population. 75–90% of the affected people have mild intellectual disability. Non-syndromic or idiopathic ID accounts for 30–50% of cases. About a quarter of cases are caused by a genetic disorder. Cases of unknown cause affect about 95 million people as of 2013.

Although little is known about the biological basis of autism, studies have revealed structural abnormalities in specific brain regions. Regions identified in the "social" brain include the amygdala, superior temporal sulcus, fusiform gyrus area and orbitofrontal cortex. Further abnormalities have been observed in the caudate nucleus, believed to be involved in restrictive behaviors, as well as in a significant increase in the amount of cortical grey matter and atypical connectivity between brain regions.

There is a mistaken belief that some vaccinations, such as the MMR, the measles/mumps vaccine, may cause autism. This was based on a research study published by Andrew Wakefield, which has been determined fraudulent and retracted. The results of this study caused some parents to take their children off the vaccines; these diseases can cause intellectual disabilities or death. The claim that some vaccinations cause autism has not been proven through multiple large-scale studies conducted in Japan, the United States, and other countries.

Deprivation from social and emotional care causes severe delays in brain and cognitive development. Studies with children growing up Romanian orphanages during Nicolae Ceauşescu's regime reveal profound effects of social deprivation and language deprivation on the developing brain. These effects are time dependent. The longer children stayed in negligent institutional care, the greater the consequences. By contrast, adoption at an early age mitigated some of the effects of earlier institutionalization (abnormal psychology).

The scientific study of the causes of developmental disorders involves many different theories. Some of the major differences between these theories involves whether or not environment disrupts normal development, or if abnormalities are pre-determined.

Normal development occurs with a combination of contributions from both the environment and genetics. The theories vary in the part each factor has to play in normal development, thus affecting how the abnormalities are caused.

One theory that supports environmental causes of developmental disorders involves stress in early childhood. Researcher and child psychiatrist Bruce D. Perry, M.D., Ph.D, theorizes that developmental disorders can be caused by early childhood traumatization. In his works he compares developmental disorders in traumatized children to adults with post-traumatic stress disorder, linking extreme environmental stress to the cause of developmental difficulties. Other stress theories suggest that even small stresses can accumulate to result in emotional, behavioral, or social disorders in children.

A 2017 study tested all 20,000 genes in about 4,300 families with children with rare developmental difficulties in the UK and Ireland in order to identify if these difficulties had a genetic cause.They found 14 new developmental disorders caused by spontaneous genetic mutations not found in either parent (such as a fault in the CDK13 gene). They estimated that about one in 300 children are born with spontaneous genetic mutations associated with rare developmental disorders.

Learning disability is a classification that includes several areas of functioning in which a person has difficulty learning in a typical manner, usually caused by an unknown factor or factors. Given the "difficulty learning in a typical manner", this does not exclude the ability to learn in a different manner. Therefore, some people can be more accurately described as having a "Learning Difference", thus avoiding any misconception of being disabled with a lack of ability to learn and possible negative stereotyping.

In the UK, the term "learning disability" generally refers to an intellectual disability, while difficulties such as dyslexia and dyspraxia are usually referred to as "learning difficulties".

While "learning disability, learning disorder" and "learning difficulty" are often used interchangeably, they differ in many ways. Disorder refers to significant learning problems in an academic area. These problems, however, are not enough to warrant an official diagnosis. Learning disability, on the other hand, is an official clinical diagnosis, whereby the individual meets certain criteria, as determined by a professional (psychologist, pediatrician, etc.). The difference is in degree, frequency, and intensity of reported symptoms and problems, and thus the two should not be confused. When the term "learning disorder" is used, it describes a group of disorders characterized by inadequate development of specific academic, language, and speech skills. Types of learning disorders include reading (dyslexia), mathematics (dyscalculia) and writing (dysgraphia).

The unknown factor is the disorder that affects the brain's ability to receive and process information. This disorder can make it problematic for a person to learn as quickly or in the same way as someone who is not affected by a learning disability. People with a learning disability have trouble performing specific types of skills or completing tasks if left to figure things out by themselves or if taught in conventional ways.

Individuals with learning disabilities can face unique challenges that are often pervasive throughout the lifespan. Depending on the type and severity of the disability, interventions, and current technologies may be used to help the individual learn strategies that will foster future success. Some interventions can be quite simplistic, while others are intricate and complex. Current technologies may require student training to be effective classroom supports. Teachers, parents, and schools can create plans together that tailor intervention and accommodations to aid the individuals in successfully becoming independent learners. School psychologists and other qualified professionals quite often help design the intervention and coordinate the execution of the intervention with teachers and parents.

Representatives of organizations committed to the education and welfare of individuals with learning disabilities are known as National Joint Committee on Learning Disabilities (NJCLD). The NJCLD used the term 'learning disability' to indicate a discrepancy between a child’s apparent capacity to learn and his or her level of achievement. Several difficulties existed, however, with the NJCLD standard of defining learning disability. One such difficulty was its belief of central nervous system dysfunction as a basis of understanding and diagnosing learning disability. This conflicted with the fact that many individuals who experienced central nervous system dysfunction, such as those with cerebral palsy, did not experience disabilities in learning. On the other hand, those individuals who experienced multiple handicapping conditions along with learning disability frequently received inappropriate assessment, planning, and instruction. The NJCLD notes that it is possible for learning disability to occur simultaneously with other handicapping conditions, however, the two should not be directly linked together or confused.

In the 1980s, NJCLD, therefore, defined the term learning disability as: a heterogeneous group of disorders manifested by significant difficulties in the acquisition and use of listening, speaking, reading, writing, reasoning or mathematical abilities. These disorders are intrinsic to the individual and presumed to be due to Central Nervous System Dysfunction. Even though a learning disability may occur concomitantly with other handicapping conditions (e.g. sensory impairment, intellectual disability, social and emotional disturbance) or environmental influences (e.g. cultural differences, insufficient/inappropriate instruction, factors) it is not the direct result of those conditions or influences.

The 2002 LD Roundtable produced the following definition:Concept of LD: Strong converging evidence supports the validity of the concept of specific learning disabilities (SLD). This evidence is particularly impressive because it converges across different indicators and methodologies. The central concept of SLD involves disorders of learning and cognition that are intrinsic to the individual. SLD are specific in the sense that these disorders each significantly affect a relatively narrow range of academic and performance outcomes. SLD may occur in combination with other disabling conditions, but they are not due primarily to other conditions, such as intellectual disability, behavioral disturbance, lack of opportunities to learn, or primary sensory deficits.The issue of defining learning disabilities has generated significant and ongoing controversy. The term "learning disability" does not exist in DSM-IV, but it has been added to DSM-5. The DSM-5 does not limit learning disorders to a particular diagnosis such as reading, mathematics and written expression. Instead, it is a single diagnosis criterion describing drawbacks in general academic skills and includes detailed specifiers for the areas of reading, mathematics, and written expression.

Intellectual disability in children can be caused by genetic or environmental factors. The individual could have a natural brain malformation or pre or postnatal damage done to the brain caused by drowning or a traumatic brain injury, for example. Nearly 30 to 50% of individuals with intellectual disability will never know the cause of their diagnosis even after thorough investigation.

Prenatal causes of intellectual disability include:

- Congenital infections such as cytomegalovirus, toxoplasmosis, herpes, syphilis, rubella and human immunodeficiency virus

- Prolonged maternal fever in the first trimester

- Exposure to anticonvulsants or alcohol

- Untreated maternal phenylketonuria (PKU)

- Complications of prematurity, especially in extremely low-birth-weight infants

- Postnatal exposure to lead

Single-gene disorders that result in intellectual disability include:

- Fragile X syndrome

- Neurofibromatosis

- Tuberous sclerosis

- Noonan's syndrome

- Cornelia de Lange's syndrome

These single-gene disorders are usually associated with atypical physical characteristics.

About 1/4 of individuals with intellectual disability have a detectable chromosomal abnormality. Others may have small amounts of deletion or duplication of chromosomes, which may go unnoticed and therefore, undetermined.

High-functioning autism is characterized by features very similar to those of Asperger syndrome. The defining characteristic most widely recognized by psychologists is a significant delay in the development of early speech and language skills, before the age of three years. The diagnostic criteria of Asperger syndrome exclude a general language delay.

Further differences in features between people with high-functioning autism and those with Asperger syndrome, include the following:

- People with HFA have a lower verbal reasoning ability

- Better visual/spatial skills (higher performance IQ) than people with Asperger syndrome

- Less deviating locomotion than people with Asperger syndrome

- People with HFA more often have problems functioning independently

- Curiosity and interest for many different things, in contrast to people with Asperger syndrome

- People with Asperger syndrome are better at empathizing with another

- The male to female ratio of 4:1 for HFA is much smaller than that of Asperger syndrome

Individuals with autism spectrum disorders, including high-functioning autism, risk developing symptoms of anxiety. While anxiety is one of the most commonly occurring mental health symptoms, children and adolescents with high functioning autism are at an even greater risk of developing symptoms.

There are other comorbidities, the presence of one or more disorders in addition to the primary disorder, associated with high-functioning autism. Some of these include depression, bipolar disorder, and obsessive compulsive disorder (OCD). In particular the link between HFA and OCD, has been studied; both have abnormalities associated with serotonin.

Observable comorbidities associated with HFA include ADHD, Tourette syndrome, and possibly criminal behavior. While the association between HFA and criminal behavior is not completely characterized, several studies have shown that the features associated with HFA may increase the probability of engaging in criminal behavior. While there is still a great deal of research that needs to be done in this area, recent studies on the correlation between HFA and criminal actions suggest that there is a need to understand the attributes of HFA that may lead to violent behavior. There have been several case studies that link the lack of empathy and social naïveté associated with HFA to criminal actions.

HFA does not cause nor include intellectual disabilities. This characteristic distinguishes HFA from the rest of the autism spectrum; between 40 and 55% of individuals with autism also have an intellectual disability.

Developmental disorders comprise a group of psychiatric conditions originating in childhood that involve serious impairment in different areas. There are several ways of using this term. The most narrow concept is used in the category "Specific Disorders of Psychological Development" in the ICD-10. These disorders comprise language disorders, learning disorders, motor disorders and autism spectrum disorders. In broader definitions ADHD is included, and the term used is neurodevelopmental disorders. Yet others include antisocial behavior and schizophrenia that begins in childhood and continues through life. However, these two latter conditions are not as stable as the other developmental disorders, and there is not the same evidence of a shared genetic liability.

Developmental disorders are present from early life. They usually improve as the child grows older, but they also entail impairments that continue through adult life. There is a strong genetic component, and more males are afflicted than females.

There are a number of factors that could potentially contribute to the development of feeding and eating disorders of infancy or early childhood. These factors include:

- Physiological – a chemical imbalance effecting the child's appetite could cause a feeding or eating disorder.

- Developmental – developmental abnormalities in oral-sensory, oral-motor, and swallowing can impact the child's eating ability and elicit a feeding or eating disorder.

- Environmental – simple issues such as inconsistent meal times can cause a feeding or eating disorder. Giving the child food that they are not developmentally acquired for can also cause these disorders. Family dysfunction and sociocultural issues could also play a role in feeding or eating disorders.

- Relational – when the child is not securely attached to the mother, it can cause feeding interactions to become disturbed or unnatural. Other factors, such as parental emotional unavailability and parental eating disorders, can cause feeding and eating disorders in their children.

- Psychological and behavioral – these factors include one involving the child's temperament. Characteristics such as being anxious, impulsive, distracted, or strong-willed personality types are ones that could affect the child's eating and cause a disorder. The individual could have learned to reject food due to a traumatic experience such as choking or being force fed.

A pervasive developmental disorder not otherwise specified (PDD-NOS) is one of the four autism spectrum disorders (ASD) and also one of the five disorders classified as a pervasive developmental disorder (PDD). According to the DSM-IV, PDD-NOS is a diagnosis that is used for "severe and pervasive impairment in the development of reciprocal social interaction or verbal and nonverbal communication skills, or when stereotyped behavior, interests, and activities are present, but the criteria are not met for a specific PDD" or for several other disorders. PDD-NOS is often called atypical autism, because the criteria for autistic disorder are not met, for instance because of late age of onset, atypical symptomatology, or subthreshold symptomatology, or all of these. Even though PDD-NOS is considered milder than typical autism, this is not always true. While some characteristics may be milder, others may be more severe.

It is common for individuals with PDD-NOS to have more intact social skills and a lower level of intellectual deficit than individuals with other PDDs. Characteristics of many individuals with PDD-NOS are:

- Communication difficulties (e.g., using and understanding language)

- Difficulty with social behavior

- Difficulty with changes in routines or environments

- Uneven skill development (strengths in some areas and delays in others)

- Unusual play with toys and other objects

- Repetitive body movements or behavior patterns

- Preoccupation with fantasy, such as imaginary friends in childhood

Nonverbal learning disorder (also known as nonverbal learning disability, NLD, or NVLD) is a learning disorder characterized by verbal strengths as well as visual-spatial, motor, and social skills difficulties. It is sometimes confused with Asperger Syndrome or high IQ. Nonverbal learning disorder has never been included in the American Psychiatric Association's "Diagnostic and Statistical Manual of Mental Disorders" or the World Health Organization's "International Classification of Diseases".

Considered to be neurologically based, nonverbal learning disorder is characterized by verbal strengths as well as visual-spatial, motor, and social skills difficulties. People with this disorder may not at times comprehend nonverbal cues such as facial expression or tone of voice. Challenges with mathematics and handwriting are common.

While various nonverbal impairments were recognized since early studies in child neurology, there is ongoing debate as to whether/or the extent to which existing conceptions of NLD provide a valid diagnostic framework. As originally presented "nonverbal disabilities" (p. 44) or "disorders of nonverbal learning" (p. 272) was a category encompassing non-linguistic learning problems (Johnson and Myklebust, 1967). "Nonverbal learning disabilities" were further discussed by Myklebust in 1975 as representing a subtype of learning disability with a range of presentations involving "mainly visual cognitive processing," social imperception, a gap between higher verbal ability and lower performance IQ, as well as difficulty with handwriting. Later neuropsychologist Byron Rourke sought to develop consistent criteria with a theory and model of brain functioning that would establish NLD as a distinct syndrome (1989).

Questions remain about how best to frame the perceptual, cognitive and motor issues associated with NLD.

The DSM-5 (Diagnostic and Statistical Manual) and ICD-10 (International Classification of Diseases) do not include NLD as a diagnosis.

Assorted diagnoses have been discussed as sharing symptoms with NLD—these conditions include Right hemisphere brain damage and Developmental Right Hemisphere Syndrome, Developmental Coordination Disorder, Social-Emotional Processing Disorder, Asperger syndrome, Gerstmann syndrome and others.

Labels for specific associated issues include visual-spatial deficit, dyscalculia, dysgraphia, as well as dyspraxia.

In their 1967 book "Learning Disabilities; Educational Principles and Practices", Doris J. Johnson and Helmer R. Myklebust characterize how someone with these kinds of disabilities appears in a classroom: "An example is the child who fails to learn the meaning of the actions of others...We categorize this child as having a deficiency in social perception, meaning that he has an inability which precludes acquiring the significance of basic nonverbal aspects of daily living, though his verbal level of intelligence falls within or above the average." (p. 272). In their chapter "Nonverbal Disorders Of Learning" (p. 272-306) are sections titled "Learning Though Pictures," (274) "Gesture," (281) "Nonverbal Motor Learning," (282) "Body Image," (285) "Spatial Orientation," (290) "Right-Left Orientation," (292) "Social Imperception," (295) "Distractibility, Perseveration, and Disinhibition." (298)

There are a variety of medical conditions affecting cognitive ability. This is a broad concept encompassing various intellectual or cognitive deficits, including intellectual disability, deficits too mild to properly qualify as intellectual disability, various specific conditions (such as specific learning disability), and problems acquired later in life through acquired brain injuries or neurodegenerative diseases like dementia. These disabilities may appear at any age.

The earliest appearance of dyscalculia is typically a deficit in the ability to know, from a brief glance and without counting, how many objects there are in a small group (see subitizing). Children as young as 5 can subitize 6 objects, especially looking at a die. However, children with dyscalculia can subitize fewer objects and even when correct take longer to identify the number than their age-matched peers.Dyscalculia often looks different at different ages. It tends to become more apparent as kids get older; however, symptoms can appear as early as preschool.

Dyscalculia is thought to be present in 3–6% of the general population, but estimates by country and sample vary somewhat. Many studies have found prevalence rates by gender to be equivalent. Those that find gender difference in prevalence rates often find dyscalculia higher in females, but some few studies have found prevalence rates higher in males.

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.

Late talker is a term used for exceptionally bright people who experience a delay in the development of speech. Commonalities include usually being boys, delayed speech development, highly educated parents, musically gifted families, puzzle-solving abilities, and lagging social development. Many high-achieving late talkers were notoriously strong willed and noncompliant as children. Late talkers can often be misdiagnosed early on as having severe ("low-functioning") autism spectrum disorder (a category known simply as "autism", prior to the DSM-5), and careful professional evaluation is necessary for differential diagnosis, according to Darold Treffert and other experts. One major difference between late talkers and low-functioning autistic children is that for late talkers, communication skills automatically reach a normal level and the child requires no further special treatment with regards to speech. Outlook for late talkers with or without intervention is generally favorable. However, late language emergence can also be an early or secondary sign of high-functioning autism spectrum disorder / Asperger syndrome, or other developmental disorders, such as attention deficit hyperactivity disorder, intellectual disability, learning disability, social communication disorder, or specific language impairment.

Einstein syndrome, a term coined by the economist Thomas Sowell, is also sometimes used to describe late talkers. The term is named after Albert Einstein (often said to have been a late talker, though with questionable evidence), whom Sowell used as the primary example of a late talker in his work. Sowell also included Edward Teller, Srinivasa Ramanujan, the mathematician Julia Robinson, Richard Feynman, and the pianists Clara Schumann and Arthur Rubinstein to be in the late talkers group. As a toddler, the scientist John Clive Ward showed similar behavioral traits to those described by Sowell, according to a brief sketch of his biography.

Sowell claimed late talkers are often inaccurately categorized as having an autism spectrum disorder (ASD), and that a small subset of late talkers are highly intelligent children with common characteristics concentrated in music, memory, math or the sciences. However, as reported by Simon Baron-Cohen, such characteristics are often found in high-functioning autism / Asperger syndrome.