Resource centre
Explore 93 guides to early development, health and everyday support. Find a topic, read online or download a PDF.
Find a resourceEmpowering Children. Supporting Families. Building Brighter Futures.
The Mariel resource library
Explore causes, signs, assessment, therapy and everyday support. Read at your pace, or save a guide for later.
93 resources in 17 topic groups
Download topic index ↓Global developmental delay (GDD) describes significant delays in at least two developmental areas in a child usually younger than 5. Areas include movement, communication, learning, relationships, and…
Online guide · 3-page PDF
Speech and language delay describes slower development of spoken sounds, words, understanding, or other communication skills. Speech is the production of sounds; language is understanding and sharing…
Online guide · 3-page PDF
Gross motor delay means slower development of large-body movements such as controlling the head, sitting, standing, walking, and changing position. It describes a developmental pattern rather than a…
Online guide · 3-page PDF
Fine motor delay describes slower development of controlled hand and finger use. These skills support reaching, grasping, releasing, turning pages, using utensils, and later drawing or writing. The goal is…
Online guide · 3-page PDF
Cognitive developmental delay describes slower progress in learning, remembering, exploring, understanding relationships, and solving age-appropriate problems. It is not a measure of a child's worth. In…
Online guide · 3-page PDF
Social-emotional developmental delay describes slower progress in skills such as shared enjoyment, responding to others, expressing feelings, and joining age-appropriate play. It is a developmental…
Online guide · 3-page PDF
Adaptive and self-care skill delay describes difficulty learning everyday activities such as feeding oneself, dressing, washing, communicating needs, and later toileting. Expectations depend on age,…
Online guide · 3-page PDF
Autism spectrum disorder (ASD) is a neurodevelopmental condition involving differences in social communication and interaction, together with restricted or repetitive patterns of behavior, interests, or…
Online guide · 3-page PDF
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental condition involving persistent patterns of inattention and/or hyperactivity and impulsivity that interfere with functioning. Many…
Online guide · 3-page PDF
Intellectual disability involves difficulties in intellectual functioning, such as reasoning and learning, together with limitations in adaptive everyday skills. It begins during the developmental period.…
Online guide · 3-page PDF
Developmental language disorder (DLD) is a persistent difficulty learning, understanding, or using language that is not explained by a known differentiating condition such as hearing loss, intellectual…
Online guide · 3-page PDF
Receptive language difficulties involve understanding spoken or signed language. A child may hear a message without fully understanding its words, grammar, or meaning. This is a descriptive communication…
Online guide · 3-page PDF
Expressive language difficulties affect sharing ideas, needs, and information through words, sentences, signs, or other language forms. They are different from difficulty pronouncing sounds, although both…
Online guide · 3-page PDF
Mixed receptive-expressive language difficulties affect both understanding language and expressing messages. The term describes a communication pattern rather than a single cause. These children may need…
Online guide · 3-page PDF
Speech sound disorders involve difficulty producing or organizing speech sounds in ways that affect intelligibility. This umbrella includes articulation and phonological disorders and can also include…
Online guide · 3-page PDF
An articulation disorder involves difficulty forming particular speech sounds, often producing distortions or substitutions. It is one type of speech sound disorder. Whether a sound is expected depends on…
Online guide · 3-page PDF
A phonological disorder involves difficulty learning or using the sound patterns of a language. A child may consistently simplify groups of sounds or use one sound in place of several others. This differs…
Online guide · 3-page PDF
Childhood apraxia of speech (CAS) is a motor speech disorder affecting planning and programming the movements for speech. Speech muscles are not necessarily weak. Children may know what they want to say but…
Online guide · 3-page PDF
Childhood dysarthria is a motor speech disorder caused by difficulty controlling the muscles used for speech. It can affect breathing, voice, resonance, articulation, and speech rhythm. It differs from…
Online guide · 3-page PDF
Childhood-onset stuttering involves interruptions in speech flow, such as repeated sounds or syllables, prolonged sounds, or blocks. Some young children show temporary disfluency while language develops. A…
Online guide · 3-page PDF
A voice disorder is a persistent change in voice quality, loudness, pitch, or effort that limits comfortable communication. A child's voice may be hoarse, breathy, strained, or unusually weak. A temporary…
Online guide · 3-page PDF
Resonance disorders involve abnormal balance or transmission of sound through the mouth and nose during speech. Speech may sound too nasal, insufficiently nasal, or muffled. This differs from the…
Online guide · 3-page PDF
Cerebral palsy (CP) is a group of conditions affecting movement and posture because of an injury or difference in the developing brain. The original brain disturbance is not progressive, but movement and…
Online guide · 3-page PDF
Developmental coordination disorder (DCD) involves persistent difficulty acquiring and carrying out coordinated motor skills that interferes with everyday activities. The difficulty is greater than expected…
Online guide · 3-page PDF
Hypotonia means reduced muscle tone, or less resistance when a joint is moved passively. A child may feel unusually floppy. Tone is different from muscle strength: low tone and weakness can coexist, but…
Online guide · 3-page PDF
Hypertonia means increased resistance when muscles and joints are moved passively. It is a clinical sign, not a stand-alone explanation of the cause. It may include different patterns, such as spasticity,…
Online guide · 3-page PDF
Spasticity is a specific form of increased muscle tone in which resistance to passive stretch depends partly on how quickly the limb is moved. It can interfere with comfort, movement, care, and…
Online guide · 3-page PDF
Spinal muscular atrophy (SMA) is a group of genetic conditions affecting motor nerve cells and causing muscle weakness. The most common form is related to SMN1. Severity and age of onset vary. Early…
Online guide · 3-page PDF
Muscular dystrophies are a group of inherited conditions causing muscle weakness and muscle damage over time. Different forms have different causes, patterns, and ages of onset. An overview label should not…
Online guide · 3-page PDF
Duchenne muscular dystrophy (DMD) is a genetic muscle condition caused by inadequate functional dystrophin. It usually affects boys, although girls and women can also have symptoms or related cardiac risks.…
Online guide · 3-page PDF
Conductive hearing loss occurs when sound is reduced as it passes through the outer or middle ear. The inner ear may still function normally. Hearing can be temporary, fluctuating, or persistent, depending…
Online guide · 3-page PDF
Sensorineural hearing loss involves the inner ear's sensory structures and/or the auditory nerve. It may be present at birth or develop later, and can affect one or both ears. Communication needs vary with…
Online guide · 3-page PDF
Mixed hearing loss combines conductive and sensorineural components. A child has both a sound-transmission difficulty in the outer or middle ear and reduced function in the inner ear or auditory pathway.…
Online guide · 3-page PDF
Auditory neuropathy spectrum disorder (ANSD) is a hearing condition in which sound detection by parts of the inner ear may be preserved, but transmission or timing of signals along the auditory pathway is…
Online guide · 3-page PDF
Persistent middle-ear fluid, also called otitis media with effusion, is fluid behind the eardrum without the usual signs of an acute ear infection. It can reduce sound transmission and affect hearing…
Online guide · 3-page PDF
Amblyopia is reduced vision that develops when the brain does not receive or use clear, balanced visual information during childhood. It often affects one eye, but can affect both. The eye may look normal.…
Online guide · 3-page PDF
Strabismus, also called a squint, means the eyes are not consistently aligned in the same direction. An eye may turn inward, outward, upward, or downward. It can be constant or intermittent. It is different…
Online guide · 3-page PDF
Refractive errors are focusing problems that make vision blurred because light is not focused clearly on the retina. Childhood examples include myopia, hyperopia, and astigmatism. They are eye conditions,…
Online guide · 3-page PDF
Astigmatism is a refractive error caused by unequal curvature of the cornea or lens, so light does not focus into one clear image. It can blur or distort vision at different distances. It may occur alone or…
Online guide · 3-page PDF
Congenital cataracts are cloudy areas in a lens present at birth or identified in early infancy. They may affect one or both eyes. A cataract that blocks useful visual input can disrupt visual development,…
Online guide · 3-page PDF
Cerebral visual impairment (CVI), also called cortical visual impairment in some contexts, involves difficulty using vision because the brain's visual pathways or processing areas are affected. The eyes may…
Online guide · 3-page PDF
Low vision is a level of visual difficulty that is not adequately corrected by ordinary glasses, contact lenses, or standard treatment alone. It does not mean no vision. A child may have useful remaining…
Online guide · 3-page PDF
Blindness describes very severe visual impairment, but definitions vary and some children classified as blind retain light perception or other useful vision. It is not a single disease. Children can develop…
Online guide · 3-page PDF
Sensory over-responsivity describes unusually strong or distressing responses to sensations such as sound, touch, light, movement, or textures. It is a descriptive pattern, not an automatic stand-alone…
Online guide · 3-page PDF
Sensory under-responsivity describes a reduced or delayed response to some sensory information. A child may seem not to notice an ordinary cue, but the explanation must be assessed. This pattern is not the…
Online guide · 3-page PDF
Sensory-seeking patterns involve frequently pursuing movement, touch, pressure, sound, or other sensations. Seeking input can be part of typical development or a helpful form of self-regulation. It becomes…
Online guide · 3-page PDF
Pediatric feeding disorder (PFD) involves oral intake that is not appropriate for a child's age and is associated with medical, nutritional, feeding-skill, or psychosocial difficulties. It is broader than…
Online guide · 3-page PDF
Pediatric dysphagia is difficulty moving food, liquids, or saliva through the swallowing process safely and efficiently. It may affect the mouth, throat, or esophagus. A child can have dysphagia with or…
Online guide · 3-page PDF
Oral-motor feeding coordination difficulties affect the movements and timing needed to suck, manage food in the mouth, chew, or drink. This is a descriptive feeding-skill concern. It may coexist with…
Online guide · 3-page PDF
Oral or food aversion describes distress, avoidance, or strong negative responses to food or experiences around the mouth. It is a descriptive concern, not a single diagnosis. Avoidance can communicate…
Online guide · 3-page PDF
Avoidant/restrictive food intake disorder (ARFID) is an eating or feeding disorder in which avoidance or restriction causes significant nutritional, growth, dependence-on-supplementation, or psychosocial…
Online guide · 3-page PDF
Growth faltering means a child's growth or weight gain is not following an appropriate pattern over time. It is a finding that needs explanation, not a diagnosis of poor caregiving. A naturally small child…
Online guide · 3-page PDF
Undernutrition means inadequate energy, protein, or other nutrients for health and growth. Malnutrition is a broader term that includes nutritional imbalance; this guide focuses on childhood undernutrition.…
Online guide · 3-page PDF
Nutritional deficiencies occur when a child does not have enough of particular nutrients for healthy body and brain function. Examples include deficiencies of iron, vitamin D, vitamin B12, iodine, or other…
Online guide · 3-page PDF
Iron deficiency means the body's iron stores are inadequate. It can occur before anemia develops. Iron supports blood production and other body and brain functions. Fatigue or developmental concerns do not…
Online guide · 3-page PDF
Iron-deficiency anemia occurs when inadequate iron limits production of healthy oxygen-carrying red blood cells. It can affect energy, growth, attention, and development. Not all anemia is caused by iron…
Online guide · 3-page PDF
Epilepsy is a brain condition involving a continuing tendency to have seizures. Seizures can affect awareness, movement, sensation, or behavior. One seizure does not automatically establish epilepsy. Some…
Online guide · 3-page PDF
Infantile epileptic spasms syndrome (IESS) is a serious epilepsy syndrome of infancy. Spasms are often brief and easy to mistake for startles or stomach discomfort. Development may slow or regress. Prompt…
Online guide · 3-page PDF
Developmental and epileptic encephalopathies (DEEs) are a group of conditions in which an underlying disorder and epileptic activity both contribute to developmental difficulties. They are not one diagnosis…
Online guide · 3-page PDF
Dravet syndrome is a rare developmental and epileptic encephalopathy that usually begins in infancy. Early development may appear typical before recurrent seizures and later developmental difficulties…
Online guide · 3-page PDF
Hydrocephalus is an abnormal buildup of cerebrospinal fluid within the brain's fluid spaces. It can increase pressure and affect brain function. Some children have developmental difficulties; others have…
Online guide · 3-page PDF
Microcephaly means a child's head circumference is substantially smaller than expected for age and sex. It is a finding with many possible explanations, rather than one disease. Development ranges from…
Online guide · 3-page PDF
Spina bifida is a group of conditions involving incomplete formation or closure of the spine during early pregnancy. Its forms differ considerably. Some cause little impairment; others affect movement,…
Online guide · 3-page PDF
Down syndrome is a genetic condition caused by extra chromosome 21 material. It affects development and is associated with particular medical risks, but each child's abilities and interests are individual.…
Online guide · 3-page PDF
Fragile X syndrome is a genetic condition that can affect learning, language, attention, sensory regulation, and social participation. Its effects vary, including between children of different sexes. Some…
Online guide · 3-page PDF
Rett syndrome is a genetic neurodevelopmental condition often recognized when a child loses previously acquired hand skills and spoken language. Movement, communication, breathing patterns, and other body…
Online guide · 3-page PDF
Angelman syndrome is a genetic condition affecting development, communication, movement, and often sleep and seizures. Spoken language is usually substantially limited, but communication can develop through…
Online guide · 3-page PDF
Prader-Willi syndrome is a genetic condition with changing needs across childhood. Infants often have low muscle tone and feeding difficulty. Later, an unusually strong drive to eat can develop, alongside…
Online guide · 3-page PDF
Williams syndrome is a genetic condition that can affect the heart and blood vessels, growth, development, and learning. Children may have an uneven profile of strengths and difficulties. Social or language…
Online guide · 3-page PDF
22q11.2 deletion syndrome is a genetic condition with a highly variable combination of medical and developmental features. It may affect the heart, palate, immune system, calcium regulation, communication,…
Online guide · 3-page PDF
Tuberous sclerosis complex (TSC) is a genetic condition that can cause growths in several organs and affect brain development. Seizures, learning differences, and behavioral or communication needs may…
Online guide · 3-page PDF
Congenital hypothyroidism means inadequate thyroid hormone production or action from birth. Thyroid hormone is important for growth and brain development. Babies may initially show few symptoms, making…
Online guide · 3-page PDF
Phenylketonuria (PKU) is an inherited metabolic condition in which phenylalanine can build up to harmful levels. Untreated high levels can affect brain development. Newborn screening and early…
Online guide · 3-page PDF
Mitochondrial disorders are a varied group of conditions affecting the cell structures that help produce usable energy. They can involve several organs, including the brain and muscles. Developmental and…
Online guide · 3-page PDF
Inherited metabolic disorders are conditions in which genetic changes disrupt the body's handling of nutrients or other substances. They include many distinct diagnoses with very different treatments. Some…
Online guide · 3-page PDF
Anxiety disorders involve fear or worry that is persistent, disproportionate to the situation, and disruptive to a child's daily life. Young children commonly have temporary fears, so context matters. A…
Online guide · 3-page PDF
Separation anxiety disorder involves developmentally excessive fear or distress about separation that persists and interferes with daily life. Some separation protest is typical in infancy and toddlerhood.…
Online guide · 3-page PDF
Selective mutism is an anxiety-related condition in which a child consistently cannot speak in certain situations despite speaking in others. It can affect learning, social participation, and access to…
Online guide · 3-page PDF
Depression can occur in young children, although its expression differs from that in adults. Persistent loss of pleasure, sadness, or irritability can affect play, relationships, sleep, and learning.…
Online guide · 3-page PDF
Trauma-related conditions describe difficulties that can follow frightening, dangerous, or overwhelming experiences. In young children, distress often appears through play, behavior, sleep, or…
Online guide · 3-page PDF
Post-traumatic stress disorder (PTSD) is a specific condition that can develop after trauma and involves persistent symptoms that disrupt functioning. Young children's symptoms and diagnostic criteria are…
Online guide · 3-page PDF
Emotional and behavioral regulation difficulties describe trouble managing feelings, impulses, or responses to stress. This is a concern to understand, not one standalone diagnosis. Young children normally…
Online guide · 3-page PDF
Persistent sleep difficulties can involve trouble settling, frequent waking, or insufficient restorative sleep that affects the child or family. Sleep changes with age, and waking is common in infancy. A…
Online guide · 3-page PDF
Obstructive sleep apnea (OSA) involves repeated partial or complete blockage of breathing during sleep. It can affect sleep quality, growth, attention, behavior, and learning. It is different from ordinary…
Online guide · 3-page PDF
Fetal alcohol spectrum disorders (FASDs) describe a range of effects associated with alcohol exposure before birth. They can involve learning, attention, regulation, growth, and daily living skills. Some…
Online guide · 3-page PDF
Congenital cytomegalovirus (CMV) infection occurs when a baby acquires CMV before birth. Many infected babies have no obvious symptoms. Some develop hearing loss or other health and developmental…
Online guide · 3-page PDF
Lead exposure can harm a child's nervous system and affect learning, attention, growth, and development. Children often have no obvious symptoms. No safe blood lead level in children has been identified.…
Online guide · 3-page PDF
Kernicterus is lasting brain injury associated with severe bilirubin toxicity, usually in the newborn period. Bilirubin causes the yellow color of jaundice, but most jaundice does not lead to kernicterus.…
Online guide · 3-page PDF
Dyslexia is a learning disorder primarily affecting accurate or fluent word reading and spelling. It is not a measure of intelligence. Preschool language and early literacy difficulties may indicate risk,…
Online guide · 3-page PDF
Dyscalculia is a term for a specific learning difficulty affecting mathematics, including understanding numbers and learning arithmetic. Diagnosis generally becomes clearer during formal schooling. Early…
Online guide · 3-page PDF
Dysgraphia is used in different ways to describe difficulties with handwriting or written production. Written-expression difficulties may also involve spelling, sentence construction, and organizing ideas.…
Online guide · 3-page PDF
Prematurity means birth before 37 completed weeks of pregnancy. It is a developmental risk factor, not a diagnosis of developmental disability. Many children born early make good progress, while some need…
Online guide · 3-page PDF
Low birth weight means a birth weight below 2,500 grams, regardless of gestational age. It may reflect prematurity, restricted growth before birth, or both. It is a risk marker rather than a developmental…
Online guide · 3-page PDF
Try fewer words or choose “All topic groups”. You can also clear the filters and browse the complete collection.
Educational information to support informed conversations with your care team. These guides do not provide an individual diagnosis or treatment plan.
More support for parents
Explore our everyday parent guides, family handbook, FAQ and podcast.
Parent guide
Organize your observations and questions.
ExploreParent guide
Prepare useful examples for a conversation.
ExploreParent guide
Start with what matters to your family.
ExploreParent guide
Learn about support and local pathways.
ExploreQuestions & answers
Read the seven questions supplied by Mariel.
ExploreAudio
Listen to the featured episode at your own pace.
ExploreOwner-supplied reading
The original handbook is available as supplied. Its clinical and numerical claims have not been independently reviewed for this website.
Use the current official resources linked in our guides for age-specific milestones and local program information.
A next step, together
If you have questions about your child’s development, we’re here to listen.
