Assessments for developmental coordination disorder typically require a developmental history, detailing ages at which significant developmental milestones, such as crawling and walking, occurred. Motor skills screening includes activities designed to indicate developmental coordination disorder, including balancing, physical sequencing, touch sensitivity, and variations on walking activities.

The American Psychiatric Association has four primary inclusive diagnostic criteria for determining if a child has developmental coordination disorder.

The criteria are as follows:

1. Motor Coordination will be greatly reduced, although the intelligence of the child is normal for the age.

2. The difficulties the child experiences with motor coordination or planning interfere with the child's daily life.

3. The difficulties with coordination are not due to any other medical condition

4. If the child does also experience comorbidities such as mental retardation; motor coordination is still disproportionally affected.

Screening tests which can be used to assess developmental coordination disorder include:-

- Movement Assessment Battery for Children (Movement-ABC – Movement-ABC 2)

- Peabody Developmental Motor Scales- Second Edition (PDMS-2)

- Bruininks-Oseretsky Test of Motor Proficiency (BOTMP-BOT-2)

- Motoriktest für vier- bis sechsjährige Kinder (MOT 4-6)

- Körperkoordinationtest für Kinder (KTK)

- Test of Gross Motor Development, Second Edition (TGMD-2)

- Maastrichtse Motoriek Test (MMT)

- Wechsler Adult Intelligence Scale (WAIS-IV)

- Wechsler Individual Achievement Test (WAIT-II)

- Test of Word Reading Efficiency (TOWRE-2)

- Developmental Coordination Disorder Questionnaire (DCD-Q)

- Children's Self-Perceptions of Adequacy in, and Predilection for Physical Activity (CSAPPA)

Currently there is no single gold standard assessment test.

A baseline motor assessment establishes the starting point for developmental intervention programs. Comparing children to normal rates of development may help to establish areas of significant difficulty.

However, research in the "British Journal of Special Education" has shown that knowledge is severely limited in many who should be trained to recognise and respond to various difficulties, including developmental coordination disorder, dyslexia and deficits in attention, motor control and perception (DAMP). The earlier that difficulties are noted and timely assessments occur, the quicker intervention can begin. A teacher or GP could miss a diagnosis if they are only applying a cursory knowledge.

"Teachers will not be able to recognise or accommodate the child with learning difficulties in class if their knowledge is limited. Similarly GPs will find it difficult to detect and appropriately refer children with learning difficulties."

Assessment will usually include an interview with the child’s caregiver, observation of the child in an unstructured setting, a hearing test, and standardized tests of language. There is a wide range of language assessments in English. Some are restricted for use by experts in speech-language pathology: speech and language therapists (SaLTs/SLTs) in the UK, speech-language pathologists (SLPs) in the US and Australia. A commonly used test battery for diagnosis of DLD is the Clinical Evaluation of Language Fundamentals (CELF).

Assessments that can be completed by a parent or teacher can be useful to identify children who may require more in-depth evaluation. The Children’s Communication Checklist (CCC–2) is a parent questionnaire suitable for assessing everyday use of language in children aged 4 years and above who can speak in sentences.

Informal assessments, such as language samples, are often used by speech-language therapists/pathologists to complement formal testing and give an indication of the child's language in a more naturalistic context. A language sample may be of a conversation or narrative retell. In a narrative language sample, an adult may tell the child a story using a wordless picture book (e.g. Frog Where Are You?, Mayer, 1969), then ask the child to use the pictures and tell the story back. Language samples can be transcribed using computer software such as the Systematic Analysis of Language Software, and then analyzed for a range of features: e.g., the grammatical complexity of the child's utterances, whether the child introduces characters to their story or jumps right in, whether the events follow a logical order, and whether the narrative includes a main idea or theme and supporting details.

Assessment will usually include an interview with the child’s caregiver, observation of the child in an unstructured setting, a hearing test, and standardized tests of language and nonverbal ability. There is a wide range of language assessments in English. Some are restricted for use by speech and language professionals (therapists or SALTs in the UK, speech-language pathologists, SLPs, in the US and Australia).

A commonly used test battery for diagnosis of SLI is the Clinical Evaluation of Language Fundamentals (CELF).

Assessments that can be completed by a parent or teacher can be useful to identify children who may require more in-depth evaluation.

The Grammar and Phonology Screening (GAPS) test is a quick (ten minute) simple and accurate screening test developed and standardized in the UK. It is suitable for children from 3;4 to 6;8 years;months and can be administered by professionals and non-professionals (including parents) alike, and has been demonstrated to be highly accurate (98% accuracy) in identifying impaired children who need specialist help vs non-impaired children. This makes it potentially a feasible test for widespread screening.

The Children’s Communication Checklist (CCC–2) is a parent questionnaire suitable for testing language skills in school-aged children.

Informal assessments, such as language samples, may also be used. This procedure is useful when the normative sample of a given test is inappropriate for a given child, for instance, if the child is bilingual and the sample was of monolingual children. It is also an ecologically valid measure of all aspects of language (e.g. semantics, syntax, pragmatics, etc.).

To complete a language sample, the SLP will spend about 15 minutes talking with the child. The sample may be of a conversation (Hadley, 1998), or narrative retell. In a narrative language sample, the SLP will tell the child a story using a wordless picture book (e.g. "Frog Where Are You?", Mayer, 1969), then ask the child to use the pictures and tell the story back.

Language samples are typically transcribed using computer software such as the Systematic Analysis of Language Software (SALT, Miller et al. 2012), and then analyzed. For example, the SLP might look for whether the child introduces characters to their story or jumps right in, whether the events follow a logical order, and whether the narrative includes a main idea or theme and supporting details.

Developmental coordination disorder is a lifelong neurological condition that is more common in males than in females, with a ratio of approximately four males to every female. The exact proportion of people with the disorder is unknown since the disorder can be difficult to detect due to a lack of specific laboratory tests, thus making diagnosis of the condition one of elimination of all other possible causes/diseases. Approximately 5–6% of children are affected by this condition.

DLD is defined purely in behavioural terms: there is no biological test. There are three points that need to be met for a diagnosis of DLD:

1. The child has language difficulties that create obstacles to communication or learning in everyday life,

2. The child's language problems are unlikely to resolve by five years of age, and

3. The problems are not associated with a known biomedical condition such as brain injury, neurodegenerative conditions, genetic conditions or chromosome disorders such as Down Syndrome, sensorineural hearing loss, or Autism Spectrum Disorder or Intellectual Disability.

For research and epidemiological purposes, specific cutoffs on language assessments have been used to document the first criterion. Tomblin et al. proposed the EpiSLI criterion, based on five composite scores representing performance in three domains of language (vocabulary, grammar, and narration) and two modalities (comprehension and production). Children scoring in the lowest 10% on two or more composite scores are identified as having language disorder.

The second criterion, persistence of language problems, can be difficult to judge in a young child, but longitudinal studies have shown that difficulties are less likely to resolve for children who have poor language comprehension, rather than difficulties confined to expressive language. In addition, children with isolated difficulties in just one of the areas noted under 'subtypes' tend to make better progress than those whose language is impaired in several areas.

The third criterion specifies that DLD is used for children whose language disorder is not part of another biomedical condition, such as a genetic syndrome, a sensorineural hearing loss, neurological disease, Autism Spectrum Disorder or Intellectual Disability – these were termed 'differentiating conditions' by the CATALISE panel. Language disorders occurring with these conditions need to be assessed and children offered appropriate intervention, but a terminological distinction is made so that these cases would be diagnosed as Language Disorder associated with ___, with the main diagnosis being specified: e.g. "Language Disorder associated with Autism Spectrum Disorder." The reasoning behind these diagnostic distinctions is discussed further by Bishop (2017).

Epidemiological surveys, in the US and Canada, estimated the prevalence of SLI in 5-year-olds at around 7 percent. However, neither study adopted the stringent 'discrepancy' criteria of the Diagnostic and Statistical Manual of Mental Disorders or ICD-10; SLI was diagnosed if the child scored below cut-off on standardized language tests, but had a nonverbal IQ of 90 or above and no other exclusionary criteria.

1. SCAN is the most common tool for diagnosing APD, and it also standardized. It is composed for four subsets: discrimination of monaurally presented single words against background noise, acoustically degraded single words, dichotically presented single words, sentence stimuli. Different versions of the test are used depending on the age of the patient.

2. Random Gap Detection Test (RGDT) is also a standardized test. It assesses an individual’s gap detection threshold of tones and white noise. The exam includes stimuli at four different frequencies (500, 1000, 2000, and 4000 Hz) and white noise clicks of 50 ms duration. It is a useful test because it provides an index of auditory temporal resolution. In children, an overall gap detection threshold greater than 20 ms means they have failed.

3. Gaps in Noise Test (GIN) also measures temporal resolution by testing the patient's gap detection threshold in white noise.

4. Pitch Patterns Sequence Test (PPT) and Duration Patterns Sequence Test (DPT) measure auditory pattern identification. The PPS has s series of three tones presented at either of two pitches (high or low). Meanwhile, the DPS has a series of three tones that vary in duration rather than pitch (long or short). Patients are then asked to describe the pattern of pitches presented.

The table below demonstrates the extensive and differential diagnosis of acquired epileptic aphasia along with Cognitive and Behavioral Regression:

Note: EEG = electroencephalographic; ESES = electrical status epilepticus of sleep; RL = receptive language; S = sociability

- Continuous spike and wave of slow-wave sleep (>85% of slow-wave sleep).

It has been discovered that APD and ADHD present overlapping symptoms. Below is a ranked order of behavioral symptoms that are most frequently observed in each disorder. Professionals evaluated the overlap of symptoms between the two disorders. The order below is of symptoms that are almost always observed. This chart proves that although the symptoms listed are different, it is easy to get confused between many of them.

There is a high rate of co-occurrence between AD/HD and CAPD. Research shows that 84% of children with APD have confirmed or suspected ADHD. Co-occurrence between ADHD and APD is 41% for children with confirmed diagnosis of ADHD, and 43% for children suspected of having ADHD.

There are tests that can indicate with high probability whether a person is a dyslexic. If diagnostic testing indicates that a person may be dyslexic, such tests are often followed up with a full diagnostic assessment to determine the extent and nature of the disorder. Tests can be administered by a teacher or computer. Some test results indicate how to carry out teaching strategies.

The syndrome can be difficult to diagnose and may be misdiagnosed as autism, pervasive developmental disorder, hearing impairment, learning disability, auditory/verbal processing disorder, attention deficit hyperactivity disorder, intellectual disability, childhood schizophrenia, or emotional/behavioral problems. An EEG (electroencephalogram) test is imperative to a diagnosis. Many cases of patients exhibiting LKS will show abnormal electrical brain activity in both the right and left hemispheres of the brain; this is exhibited frequently during sleep. Even though an abnormal EEG reading is common in LKS patients, a relationship has not been identified between EEG abnormalities and the presence and intensity of language problems. In many cases however, abnormalities in the EEG test has preceded language deterioration and improvement in the EEG tracing has preceded language improvement (this occurs in about half of all affected children). Many factors inhibit the reliability of the EEG data: neurologic deficits do not closely follow the maximal EEG changes in time.

The most effective way of confirming LKS is by obtaining overnight sleep EEGs, including EEGs in all stages of sleep. Many conditions like demyelination and brain tumors can be ruled out by using magnetic resonance imaging (MRI). In LKS, fluorodeoxyglucose (FDG) and positron emission tomography (PET) scanning can show decreased metabolism in one or both temporal lobes - hypermetabolism has been seen in patients with acquired epileptic aphasia.

Most cases of LKS do not have a known cause. Occasionally, the condition may be induced secondary to other diagnoses such as low-grade brain tumors, closed-head injury, neurocysticercosis, and demyelinating disease. Central Nervous System vasculitis may be associated with this condition as well.

Classifying speech into normal and disordered is more problematic than it first seems. By a strict classification, only 5% to 10% of the population has a completely normal manner of speaking (with respect to all parameters) and healthy voice; all others suffer from one disorder or another.

There are three different levels of classification when determining the magnitude and type of a speech disorders and the proper treatment or therapy:

1. Sounds the patient can produce

1. Phonemic – can be produced easily; used meaningfully and constructively

2. Phonetic – produced only upon request; not used consistently, meaningfully, or constructively; not used in connected speech

2. Stimulate sounds

1. Easily stimulated

2. Stimulate after demonstration and probing (i.e. with a tongue depressor)

3. Cannot produce the sound

1. Cannot be produced voluntarily

2. No production ever observed

In most cases the cause is unknown. However, there are various known causes of speech impediments, such as "hearing loss, neurological disorders, brain injury, intellectual disability, drug abuse, physical impairments such as cleft lip and palate, and vocal abuse or misuse."

The diagnosis of frontal lobe disorder can be divided into the following three categories:

- Clinical history

Frontal lobe disorders may be recognized through a sudden and dramatic change in a person's personality, for example with loss of social awareness, disinhibition, emotional instability, irritability or impulsiveness. Alternatively the disorder may become apparent because of mood changes such as depression, anxiety or apathy.

- Examination

On mental state examination a person with frontal lobe damage may show speech problems, with reduced verbal fluency. Typically the person is lacking in insight and judgment, but does not have marked cognitive abnormalities or memory impairment (as measured for example by the mini-mental state examination). With more severe impairment there may be echolalia or mutism. Neurological examination may show primitive reflexes (also known as frontal release signs) such as the grasp reflex. Akinesia (lack of spontaneous movement) will be present in more severe and advanced cases.

- Further investigation

A range of neuropsychological tests are available for clarifying the nature and extent of frontal lobe dysfunction. For example, concept formation and ability to shift mental sets can be measured with the Wisconsin Card Sorting Test, planning can be assessed with the Mazes subtest of the WISC. Individuals with Pick's disease will show frontal cortical atrophy on MRIs. Frontal impairment due to head injuries, tumours or cerebrovascular disease will also be apparent on brain imaging.

Many normed assessments can be used in evaluating skills in the primary academic domains: reading, including word recognition, fluency, and comprehension; mathematics, including computation and problem solving; and written expression, including handwriting, spelling and composition.

The most commonly used comprehensive achievement tests include the Woodcock-Johnson IV (WJ IV), Wechsler Individual Achievement Test II (WIAT II), the Wide Range Achievement Test III (WRAT III), and the Stanford Achievement Test–10th edition. These tests include measures of many academic domains that are reliable in identifying areas of difficulty.

In the reading domain, there are also specialized tests that can be used to obtain details about specific reading deficits. Assessments that measure multiple domains of reading include Gray's Diagnostic Reading Tests–2nd edition (GDRT II) and the Stanford Diagnostic Reading Assessment. Assessments that measure reading subskills include the Gray Oral Reading Test IV – Fourth Edition (GORT IV), Gray Silent Reading Test, Comprehensive Test of Phonological Processing (CTOPP), Tests of Oral Reading and Comprehension Skills (TORCS), Test of Reading Comprehension 3 (TORC-3), Test of Word Reading Efficiency (TOWRE), and the Test of Reading Fluency. A more comprehensive list of reading assessments may be obtained from the Southwest Educational Development Laboratory.

The purpose of assessment is to determine what is needed for intervention, which also requires consideration of contextual variables and whether there are comorbid disorders that must also be identified and treated, such as behavioral issues or language delays. These contextual variables are often assessed using parent and teacher questionnaire forms that rate the students' behaviors and compares them to standardized norms.

However, caution should be made when suspecting the person with a learning disability may also have dementia, especially as people with Down's syndrome may have the neuroanatomical profile but not the associated clinical signs and symptoms. Examination can be carried out of executive functioning as well as social and cognitive abilities but may need adaptation of standardized tests to take account of special needs.

Dyslexic children require special instruction for word analysis and spelling from an early age. While there are fonts that may help people with dyslexia better understand writing, this might simply be due to the added spacing between words. The prognosis, generally speaking, is positive for individuals who are identified in childhood and receive support from friends and family.

Apraxia of speech can be diagnosed by a speech language pathologist (SLP) through specific exams that measure oral mechanisms of speech. The oral mechanisms exam involves tasks such as pursing lips, blowing, licking lips, elevating the tongue, and also involves an examination of the mouth. A complete exam also involves observation of the patient eating and talking. SLPs do not agree on a specific set of characteristics that make up the apraxia of speech diagnosis, so any of the characteristics from the section above could be used to form a diagnosis. Patients may be asked to perform other daily tasks such as reading, writing, and conversing with others. In situations involving brain damage, an MRI brain scan also helps identify damaged areas of the brain.

A differential diagnosis must be used in order to rule out other similar or alternative disorders. Although disorders such as expressive aphasia, conduction aphasia, and dysarthria involve similar symptoms as apraxia of speech, the disorders must be distinguished in order to correctly treat the patients. While AOS involves the motor planning or processing stage of speech, aphasic disorders can involve other language processes.

According to Ziegler et al., this difficulty in diagnosis derives from the unknown causes and function of the disorder, making it hard to set definite parameters for AOS identification. Specifically, he explains that oral-facial apraxia, dysarthria, and aphasic phonological impairment are the three distinctly different disorders that cause individuals to display symptoms that are often similar to those of someone with AOS, and that these close relatives must be correctly ruled out by a Speech Language Pathologist before AOS can be given as a diagnosis. In this way, AOS is a diagnosis of exclusion, and is generally recognized when all other similar speech sound production disorders are eliminated.

In cases of acute AOS (stroke), spontaneous recovery may occur, in which previous speech abilities reappear on their own. All other cases of acquired AOS require a form of therapy; however the therapy varies with the individual needs of the patient. Typically, treatment involves one-on-one therapy with a speech language pathologist (SLP). For severe forms of AOS, therapy may involve multiple sessions per week, which is reduced with speech improvement. Another main theme in AOS treatment is the use of repetition in order to achieve a large amount of target utterances, or desired speech usages.

There are various treatment techniques for AOS. One technique, called the Linguistic Approach, utilizes the rules for sounds and sequences. This approach focuses on the placement of the mouth in forming speech sounds. Another type of treatment is the Motor-Programming Approach, in which the motor movements necessary for speech are practiced. This technique utilizes a great amount of repetition in order to practice the sequences and transitions that are necessary in between production of sounds.

Research about the treatment of apraxia has revealed four main categories: articulatory-kinematic, rate/rhythm control, intersystemic facilitation/reorganization treatments, and alternative/augmentative communication.

- Articulatory-kinematic treatments almost always require verbal production in order to bring about improvement of speech. One common technique for this is modeling or repetition in order to establish the desired speech behavior. Articulatory-kinematic treatments are based on the importance of patients to improve spatial and temporal aspects of speech production.

- Rate and rhythm control treatments exist to improve errors in patients’ timing of speech, a common characteristic of Apraxia. These techniques often include an external source of control like metronomic pacing, for example, in repeated speech productions.

- Intersystemic reorganization/facilitation techniques often involve physical body or limb gestural approaches to improve speech. Gestures are usually combined with verbalization. It is thought that limb gestures may improve the organization of speech production.

- Finally, alternative and augmentative communication approaches to treatment of apraxia are highly individualized for each patient. However, they often involve a "comprehensive communication system" that may include "speech, a communication book aid, a spelling system, a drawing system, a gestural system, technologies, and informed speech partners".

One specific treatment method is referred to as PROMPT. This acronym stands for Prompts for Restructuring Oral Muscular Phonetic Targets, and takes a hands on multidimensional approach at treating speech production disorders. PROMPT therapists integrate physical-sensory, cognitive-linguistic, and social-emotional aspects of motor performance. The main focus is developing language interaction through this tactile-kinetic approach by using touch cues to facilitate the articulatory movements associated with individual phonemes, and eventually words.

One study describes the use of electropalatography (EPG) to treat a patient with severe acquired apraxia of speech. EPG is a computer-based tool for assessment and treatment of speech motor issues. The program allows patients to see the placement of articulators during speech production thus aiding them in attempting to correct errors. Originally after two years of speech therapy, the patient exhibited speech motor and production problems including problems with phonation, articulation, and resonance. This study showed that EPG therapy gave the patient valuable visual feedback to clarify speech movements that had been difficult for the patient to complete when given only auditory feedback.

While many studies are still exploring the various treatment methods, a few suggestions from ASHA for treating apraxia patients include the integration of objective treatment evidence, theoretical rationale, clinical knowledge and experience, and the needs and goals of the patient

Another method implemented to test for aprosodia involves having questionnaires filled out by those close to the patient. The doctors and nurses taking care of a patient are also requested to fill out a questionnaire if aprosodia is suspected. This diagnosis method occurs more as an indicator that the aprosodia battery should be administered rather than being used as a singular diagnosis tool. Implementation of the questionnaire is expected to become more widespread as aprosodia is revealed to be a side-effect of more diseases.

TMoA is diagnosed by the referring physician and speech-language pathologist (SLP). The overall sign of TMoA is nonfluent, reduced, fragmentary echoic, and perseverative speech with frequent hesitations and pauses. Patients with TMoA also have difficulty initiating and maintaining speech. However, speech articulation and auditory comprehension remain typical. The hallmark sign of TMoA is intact repetition in the presence of these signs and symptoms.

TMoA, or any other type of aphasia, is identified and diagnosed through the screening and assessment process. Screening can be conducted by a SLP or other professional when there is a suspected aphasia. The screening does not diagnose aphasia, rather it points to the need for a further comprehensive assessment. A screening typically includes evaluation of oral motor functions, speech production skills, comprehension, use of written and verbal language, cognitive communication, swallowing, and hearing. Both the screening and assessment must be sensitive to the patient’s linguistic and cultural differences. An individual will be recommended to receive a comprehensive assessment if their screening shows signs of aphasia. Under the American Speech-Language-Hearing Association (ASHA) and World Health Organization (WHO) guidelines and the "International Classification of Functioning, Disability and Health" (ICF) framework, the comprehensive assessment encompasses not only speech and language, but also impairments in body structure and function, co-morbid deficits, limitations in activity and participation, and contextual (environmental and personal) factors. The assessment can be static (current functioning) or dynamic (ongoing) and the assessment tools can be standardized or nonstandardized. Typically, the assessment for aphasia includes a gathering of a case history, a self-report from the patient, an oral-motor examination, assessment of expressive and receptive language in spoken and written forms, and identification of facilitators and barriers to patient success. From this assessment, the SLP will determine type of aphasia and the patient's communicative strengths and weaknesses and how their diagnosis may impact their overall quality of life.

Loss of language and skills related to social interaction and self-care are serious. The affected children face ongoing disabilities in certain areas and require long term care. Treatment of CDD involves both behavior therapy, environmental therapy and medications.

- Behavior therapy: The main aim of Applied Behavior Analysis (ABA) is to systematically teach the child to relearn language, self-care and social skills. The treatment programs designed in this respect "use a system of rewards to reinforce desirable behaviors and discourage problem behavior." ABA programs may be designed by a board-certified specialist in behavior analysis called a "BCBA" (Board Certified Behavior Analyst), but ABA is also widely used by a number of other health care personnel from different fields like psychologists, speech therapists, physical therapists and occupational therapists with differing levels of expertise. Parents, teachers and caregivers are instructed to use these behavior therapy methods at all times.

- Environmental Therapy: Sensory Enrichment Therapy uses enrichment of the sensory experience to improve symptoms in autism, many of which are common to CDD.

- Medications: There are no medications available to directly treat CDD. Antipsychotic medications are used to treat severe behavior problems like aggressive stance and repetitive behavior patterns. Anticonvulsant medications are used to control seizures.

About half of parents of children with ASD notice their child's unusual behaviors by age 18 months, and about four-fifths notice by age 24 months. According to an article, failure to meet any of the following milestones "is an absolute indication to proceed with further evaluations. Delay in referral for such testing may delay early diagnosis and treatment and affect the long-term outcome".

- No babbling by 12 months.

- No gesturing (pointing, waving, etc.) by 12 months.

- No single words by 16 months.

- No two-word (spontaneous, not just echolalic) phrases by 24 months.

- Any loss of any language or social skills, at any age.

The United States Preventive Services Task Force in 2016 found it was unclear if screening was beneficial or harmful among children in whom there is no concerns. The Japanese practice is to screen all children for ASD at 18 and 24 months, using autism-specific formal screening tests. In contrast, in the UK, children whose families or doctors recognize possible signs of autism are screened. It is not known which approach is more effective. Screening tools include the Modified Checklist for Autism in Toddlers (M-CHAT), the Early Screening of Autistic Traits Questionnaire, and the First Year Inventory; initial data on M-CHAT and its predecessor, the Checklist for Autism in Toddlers (CHAT), on children aged 18–30 months suggests that it is best used in a clinical setting and that it has low sensitivity (many false-negatives) but good specificity (few false-positives). It may be more accurate to precede these tests with a broadband screener that does not distinguish ASD from other developmental disorders. Screening tools designed for one culture's norms for behaviors like eye contact may be inappropriate for a different culture. Although genetic screening for autism is generally still impractical, it can be considered in some cases, such as children with neurological symptoms and dysmorphic features.

According to the DSM-IV-TR, communication disorders are usually first diagnosed in childhood or adolescence though they are not limited as childhood disorders and may persist into adulthood. They may also occur with other disorders.

Diagnosis involves testing and evaluation during which it is determined if the scores/performance are "substantially below" developmental expectations and if they "significantly" interfere with academic achievement, social interactions and daily living. This assessment may also determine if the characteristic is deviant or delayed. Therefore, it may be possible for an individual to have communication challenges but not meet the criteria of being "substantially below" criteria of the DSM IV-TR.

It should also be noted that the DSM diagnoses do not comprise a complete list of all communication disorders, for example, auditory processing disorder is not classified under the DSM or ICD-10.

The following diagnoses are included in the communication disorders:

- Expressive language disorder – Characterized by difficulty expressing oneself beyond simple sentences and a limited vocabulary. An individual understands language better than their ability to use it; they may have a lot to say but have difficulties organizing and retrieving the words to get an idea across beyond what is expected for their developmental stage.

- Mixed receptive-expressive language disorder – problems comprehending the commands of others.

- Stuttering – a speech disorder characterized by a break in fluency, where sounds, syllables or words may be repeated or prolonged.

- Phonological disorder – a speech sound disorder characterized by problems in making patterns of sound errors, i.e. "dat" for "that".

- Communication disorder NOS (not otherwise specified) – the DSM-IV diagnosis in which disorders that do not meet the specific criteria for the disorder listed above may be classified.

While infection with rubella during pregnancy causes fewer than 1% of cases of autism, vaccination against rubella can prevent many of those cases.

In a typical 2-year-old child, about 50% of speech may be intelligible. A 4-year-old child's speech should be intelligible overall, and a 7-year-old should be able to clearly produce most words consistent with community norms for their age. Misarticulation of certain difficult sounds ("l", "r",

"s", "z", "th", "ch", "dzh", and "zh") may be normal up to 8 years. Children with speech sound disorder have pronunciation difficulties inappropriate for their age, and the difficulties are not caused by hearing problems, congenital deformities, motor disorders or selective mutism.

The DSM-5 diagnostic criteria are as follows:

- A. Persistent difficulty with speech sound production that interferes with speech intelligibility or prevents verbal communication of messages.

- B. The disturbance causes limitations in effective communication that interfere with social participation, academic achievement, or occupational performance, individually or in any combination.

- C. Onset of symptoms is in the early developmental period.

- D. The difficulties are not attributable to congenital or acquired conditions, such as cerebral palsy, cleft palate, deafness or hearing loss, traumatic brain injury, or other medical or neurological conditions.

For most children, the disorder is not lifelong and speech difficulties improve with time and speech-language treatment. Prognosis is poorer for children who also have a language disorder, as that may be indicative of a learning disorder.