Principal author: Jean M. Thomas, M.D., M.S.W. This summary was developed by the Work Group on Quality Issues: John E. Dunne, M.D., Chair; Valerie Arnold, M.D., R. Scott Benson, M.D., William Bernet, M.D., Oscar Bukstein, M.D., Joan Kinlan, M.D., and Jon McClellan, M.D., and additional authors: Anne L. Benham, M.d., Margaret Gean, M.D., Joan Luby, M.D., Klaus Minde, M.D., Sylvia Turner, M.D., and Harry H. Wirght, M.D. AACAP Staff: L. Elizabeth Sloan, L.P.C. The full text of the Practice Parameters for the Psychiatric Assessment of Infants and Toddlers (0 - 36 months) is available to Academy members on the World Wide Web (www.aacap.org) and appears in the October 1997 supplement to the JAACAP. The full text of these parameters was reviewed at the 1996 Annual Meeting of the American Academy of Child and Adolescent Psychiatry. Both the full text and this Summary were approved by AACAP Council on June 2, 1997. © 1997 by the American Academy of Child and Adolescent Psychiatry.
ABSTRACT
This summary describes the psychiatric assessment of infants and toddlers (0-36 months) and supports the growth of infant and toddler psychiatry, a rapidly developing field. Infants and toddlers are brought to clinical attention because of concerns about emotional, behavioral, relational, or developmental difficulties. It is axiomatic that the infant or toddler must be understood, evaluated, and treated within the context of the family. A perspective that is developmental, relational, and multidimensional and that borrows from the knowledge of multiple disciplines is essential. Collaborative efforts support the urgent need and incomparable opportunity to understand and to intervene early and preventively with young children and their families. Key words: infant psychiatry, infant, toddler, interdisciplinary assessment, practice parameters, guidelines.
These parameters give the clinician direction in the psychiatric assessment of infants and toddlers (0 - 36 months). Recommendations are based on extensive review of the scientific literature and consensus among clinical experts in the field. The literature review, including references, and the rationale for specific recommendations are contained in the complete document (American Academy of Child and Adolescent Psychiatry, 1997). The field of infant and toddler psychiatry is young and rapidly developing. Collaborative, intertheoretical, interdisciplinary, interinstitutional, and international efforts support the urgent need and incomparable opportunity to understand and to intervene early and preventively with young children and their families. The practice parameters summarized here are intended as a vehicle for sharing with clinicians the expertise of child and adolescent psychiatrists and other clinicians who specialize in clinical work with infants, toddlers, and their families. These parameters suggest structure and content for the family interview; guide observations of interactions and relationships; present the Infant and Toddler Mental Status Exam (ITMSE); describe the Diagnostic Classification: 0 to 3 (DC:0-3) (Zero to Three, 1994); discuss adjunctive, helpful standardized instruments; suggest interdisciplinary team and referral strategies for integrating complex multidimensional information; and guide the diagnostic formulation process and development of a treatment plan. Challenges encountered in developing these parameters included: the bringing together of experts in an emerging field for which knowledge is still largely clinical, rapidly developing, and minimally represented in the literature; and concisely but thoroughly presenting knowledge and clinical strategies to practitioners for whom work with very young children is new or who are in solo practice and do not have access to specialized professionals or assessment facilities.
CONSIDERATIONS IN THE ASSESSMENT OF INFANTS AND TODDLERS
By design, assessment and intervention with infants and toddlers is a unified process oriented toward prevention. Since infancy and toddlerhood are a time of rapid change and lay the foundation for future development, the clinician's primary effort is aimed at facilitating the child's rapid change toward healthy development and strengthening parental and extended environmental support systems. Parents are primary in the treatment team because infants and toddlers are maximally dependent on parents. Facilitation of change, therefore, must be accomplished primarily through the parents. A multidimensional perspective that borrows from pediatrics, developmental psychology, speech and language therapy, occupational therapy, physical therapy, and other disciplines is essential to effective work with very young children, who are able to provide only limited behavioral and verbal clues to help the clinician understand complex mutually influencing etiologic factors. In assessing infants and toddlers, a developmental perspective is essential to differentiate normality from risk and pathology. In addition, a relationship perspective is essential to understand the power of relationships both in the child's development and in collaborative assessment, intervention, and treatment planning with the parents. Multiple assessments over time often are needed because infants and toddlers change rapidly in response to internal and external stressors. For infants, the most frequent referral concerns are: dysregulation of physiologic function, including fussiness or colicky behavior; feeding and sleeping problems; and failure to thrive. For toddlers, the most frequent referral concerns are: behavioral disturbances, including aggression, defiance, impulsivity, and over activity. In addition, constitutional factors, including developmental delays and subtle physiologic, sensory, and motor-processing problems often derail expected developmental progress and bring young children to clinical attention. Problems with "goodness of fit" between the child's constitutional attributes and temperament and the parents' expectations create relationship difficulties that also may lead to referral. Infants and toddlers must always be understood, evaluated, and treated in the context of the family or primary caregiving unit and within additional significant contexts, including relationships with other important caregivers and extended family; school; day care center; and the larger culture. The family's alliance with the evaluating clinician provides a context for the assessment and intervention process. Through this relationship, the clinician and parents together observe and facilitate the family's behavioral, affective, and psychological responses to each other, clarify concerns about the child, and mutually develop a treatment plan. It is helpful to keep in mind that the parents of infants and toddlers often feel anxious or guilty because they think that problems existing in a young child may imply that their parenting skills are inadequate. The purposes of the psychiatric assessment of infants and toddlers include developing a shared understanding of the core concerns and other factors leading to the referral; determining whether psychopathology or conditions that lead to risk or vulnerability are present; establishing a developmentally based differential diagnosis and an ongoing mutual process of formulation that helps organize the parents' understanding of their experience with the child; and developing a treatment plan that addresses the parents' explicit and implicit expectations and facilitates parent--child relationships that support the child's healthy development. To accomplish these purposes, the aims of the diagnostic assessment are: to establish with the parents an ongoing therapeutic relationship built on respect for the parents' knowing their child, being a central influence in their child's life, wanting to make a better life for their child, and having unique values, preferences, and cultural ideals; to assess the nature, severity, and developmental impact of the child's behavioral difficulties, functional impairment, or subjective distress on the child and on the family; and to identify transactional, mutually influencing, biopsychosocial, individual, family, and sociocultural risk and protective factors that may, in the process of development, contribute to or ameliorate the presenting concerns.
ASSESSMENT
Assessment of an infant or toddler requires gathering data from those who are most familiar with the child's current and past functioning, including the child and his or her parents or other primary caregivers. The assessment format may vary but should always be responsive to the needs of the family. For example, parents often are interviewed with the infant or toddler present, but may be interviewed alone.
The Family Interview
The interview format should allow the clinician to explore the parents' explicit and implicit concerns, including their account of the reason for the referral, the child's current difficulties, and the impact of the child's symptoms on each parent, the parental couple, and the family as a whole; obtain a history of the child's past and current development in the context of his or her family; gather a history of the parents' childhood experiences of being parented and assess the degree to which these contribute to their view of the child's present behavior; obtain a picture of the biopsychosocial functioning of the parents and family within their home, community, and wider culture; gather data on familial medical and psychiatric disorders that may be of genetic or environmental significance for the etiology or treatment of the child's difficulties; and observe the parents with their child during free play and structured activity.
Reason for Referral
Parents either call for help directly, or are referred by medical, educational, or social service personnel with whom the parents have shared their concerns. The parents' account of the child's presenting difficulties and their expectations (explicit and implicit) of how the clinician may help are of primary importance. History-taking should focus not only on the child's difficulties and symptoms, but equally on his or her strengths of behavioral organization and areas of good adjustment. An approach that identifies positive attributes of the child and the caregiving environment helps enhance the parents' self-esteem and supports the working alliance between the clinician and the parents.
Developmental History
The clinician should obtain a detailed history of all developmental aspects pertaining to the biological, cognitive, temperamental, and socio-emotional life of the infant or toddler, with special focus on early concerns that may relate to the presenting concerns. Areas covered should include the child's physical, cognitive, and emotional development; the child's early behavioral organization; the child's degree of individuation; the child's unique strengths and vulnerabilities; and the child's response to previous stressors.
Family Relational History
Although the relationship between child and parents is important to psychiatric evaluations of children at any age, it is particularly critical to the evaluation of the infant or toddler. The young child's profound dependence on the parents places them in a key role to facilitate the healthy development of the child across multiple domains. The parents' perceptions, potential distortions, attitudes, and expectations of the child should be assessed thoroughly, especially since the history is expected to reflect perceptual bias. Reviewing the parents' perceptions of their own early relationship histories can uncover both the origins of parenting style, as well as the potential symbolic value of the child to each parent.
Clinical Observation
Observation of the child interacting with the parents, with a focus on the quality of the parent--child behavioral and affective interactions, is central to the assessment process. Initial observations are usually obtained during history-taking with the family. For further observation, an interactive play setting is necessary. A small, comfortable playroom with a variety of age appropriate toys, but not an overwhelming number, is most helpful. Carpeting facilitates both children and adults playing on the floor. It is imperative for the examiner to inform the parents about the nature and purpose of the play session and to ask the parents to interact with the child, as much as possible, as they would at home. At least 15 to 20 minutes of family play observation is needed. Unstructured parent--child or family play provides optimal opportunity for interactional observation. A variety of other approaches, including structured activities and the child's response to brief parental separation and reunion, may also be useful, depending on the child's developmental age and the nature of the problem. The parents' and the child's capacity for and interest in interpersonal relatedness are assessed in the context of interactive play. Clinically relevant dimensions of parent and child behaviors, and use of videotaping as an adjunct to interactional assessment, are detailed in the full parameters.
Infant and Toddler Mental Status Exam
The systematic observation of infants and toddlers is a critical source of information for diagnosis and treatment planning and should encompass individual and interactional behaviors and the emotional and developmental functioning of the child. One tool developed for this purpose is the Infant and Toddler Mental Status Exam (ITMSE) (see Table 1), which helps clinicians organize and systematize observations of young children typically made in a naturalistic or play situation. The ITMSE highlights, with examples, how traditional categories of the mental status exam for adults and older children may be adapted to observations of infants and toddlers. New categories, including sensory and state regulation, reflecting important areas of infant and toddler development and of disorders in young children, have been elaborated. In focusing on both individual and interactional behaviors and on the emotional and developmental functioning of the infant, the ITMSE may be helpful to clinicians from varying disciplines.
Standardized Instruments
Standardized instruments may augment the clinician's understanding of many aspects of biopsychosocial and cultural risk and protective factors. Although there are standardized assessment tools for infants and toddlers, their usefulness and suitability in routine clinical practice have not been clearly defined. Standardized instruments may be used as part of comprehensive assessment but should not be the sole basis for diagnosis or treatment planning. In addition, standardized instruments must be used within a developmental framework, guided by the principle that infants and toddlers must be understood in the context of the relationships within which they are developing. The full parameters include a table that provides detailed information about the standardized measures used most frequently in the clinical assessment of infants and toddlers.
Interdisciplinary Assessment and Referral
Interdisciplinary assessment is ideal, given the interaction between the individual, the family, the larger environment, and the risk and protective factors that may contribute to the presenting concerns. Assessments of infants and toddlers may be done by an established interdisciplinary team or by a solo practitioner with adjunctive assessments. The adjunctive assessments may include assessments in other settings (home, child care agency, or school) and by other disciplines, including pediatrics, developmental pediatrics, psychology, neurology, genetics, nutrition, ophthalmology, audiology, speech and language therapy, occupational therapy, physical therapy, and social and educational services. In many communities, assessment, screening, and coordination programs (federally authorized in all states for children ages 0 through 2 years) have developed referral networks for appropriate assessment and referral services.
DIAGNOSTIC FORMULATION
The diagnostic formulation represents the clinician's synthesis of the biopsychosocial and cultural influences that contribute to, maintain, or ameliorate the infant's or toddler's difficulties. When answers to these questions are provisional, a differential diagnosis provides a decision tree by which diagnosis and treatment options may be clarified over time. Diagnostic classification schemes are evolving as data and understanding in this field progress. Categories in the International Classification of Diseases, 10th Edition (ICD-10) (World Health Organization, 1992) parallel those of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) (American Psychiatric Association, 1994). Both lack diagnostic criteria and time frames specific to infants and toddlers. The Diagnostic Classification: 0 to 3 (DC:0-3) (Zero to Three, 1994) is the newest diagnostic classification. DC:0-3 proposes an evolving developmentally appropriate multiaxial framework intended to complement the DSM-IV. Preliminary data collected by the Zero to Three/National Center for Infants, Toddlers, and Families' interdisciplinary Diagnostic Classification Task Force guided the development of the diagnostic criteria. Plans for standardized training, ongoing data collection, and field testing for the DC:0-3 are currently being developed (Zero to Three, 1994). DC:0-3 contributes axes and diagnostic categories that define new constructs arising out of clinical and research experience with infants, toddlers, and their families. New Axis I categories include Regulatory Disorders and Multisystem Developmental Disorders. Regulatory Disorders define disorders that are constitutionally and maturationally based sensory, sensorimotor, or organizational processing problems associated with difficulties in regulating behavior. Multisystem Developmental Disorders offers an alternative to pervasive developmental disorders (DSM-IV and ICD-10) for young children with significant impairment in relating, significant motor and sensory processing difficulties, yet some potential for closeness. Axis II, Relationship Classification, may be used to describe relationship disorders or patterns of relating with each signficant parent figure or caregiver. Axis V, Functional Emotional Developmental Level, describes the child's capacity to organize experience (Zero to Three, 1994). The diagnostic formulation expands categorical diagnosis by identifying, to the fullest extent possible, the predisposing factors and current precipitants of the infant's difficulties. The formulation and recommendation processes evolve collaboratively with the family as a continuation of the assessment process.
TREATMENT PLANNING
On the basis of the findings, diagnostic formulation, and available resources, treatment recommendations are developed with the family. The resources available to a family, as well as the unique combination of individual and family capacities for learning and change, are considered. The summarizing discussion with the parents reviews the complexity of the assessment process, including the interdisciplinary, developmental, and multigenerational elements. The infant's attachment; temperament; and social, emotional, cognitive, physical, and language development, are characterized. Relative strengths and weaknesses are clarified. Risk factors, protective factors, socio-cultural experience, and biological factors are components of the discussion. The discussion of findings, diagnostic formulation, and recommendations may require more than one session. The parents' and other caregivers' explicit and implicit expectations help guide selection of treatments. An individualized treatment plan is designed to capitalize on the strengths of the child, the parents, and the extended environmental context. Further assessments, treatment referrals, and communication of findings to outside sources should be discussed as part of the treatment planning process. Sharing the findings with other providers, including pediatricians, day care workers, social service personnel, or parents' mental health providers, helps coordinate the complex environmental support system young children need.
Figure 1. INFANT AND TODDLER MENTAL STATUS EXAM
1. Appearance: Size; level of nourishment; dress and hygiene; apparent maturity compared to age; dysmorphic features, e.g., facies, eye and ear shape and placement, epicanthal folds, digits etc., abnormal head size; cutaneous lesions. 2. Apparent Reaction to Situation (Note where evaluation takes place and with whom.) A. Initial reaction to setting and to strangers: Explores; freezes; cries; hides face; acts curious, excited, apathetic, or anxious (describe). B. Adaptation 1. Exploration: When and how child begins exploring faces, toys, stranger. 2. Reaction to transitions: From unstructured to structured activity; when examiner begins to play with infant; cleaning up; leaving. 3. Self-Regulation A. State regulation: An infant's state of consciousness ranges from deep sleep through alert stages to intense crying. Predominant state and range of states observed during session; patterns of transition, e.g., smooth vs. abrupt; capacity for being soothed and self-soothing; capacity for quiet alert state. (Some of these categories also apply to toddlers.) B. Sensory regulation: Reaction to sounds, sights, smells, light and firm touch; hyper- or hypo-responsiveness (if observed) and type of response, including apathy, withdrawal, avoidance, fearfulness, excitability, aggression or marked behavioral change; excessive seeking of particular sensory input. C. Unusual behaviors: Mouthing after 1 year of age; head banging; smelling objects; spinning; twirling; hand-flapping; finger-flicking; rocking; toe walking; staring at lights or spinning objects; repetitive, perseverative or bizarre verbalizations or behaviors with objects or people; hair pulling; ruminating; or breath-holding. D. Activity level: Overall level and variability (Note that toddlers often incorrectly are called hyperactive.) Describe behavior, e.g., squirming constantly in parent's arms; sitting quietly on floor or in infant seat; constantly on the go; climbing on desk and cabinets; exploring the room; pausing to play with each of 6 to 8 toys. E. Attention span: Capacity to maintain attentiveness to an activity or interaction; longest and average length of sustained attention to a given toy or activity; distractibility. Infants: Visual fixing and following at 1 month; tracking at 2 to 3 months; attention to own hands or feet and faces; duration of exploration of object with hands or mouth. F. Frustration tolerance: Ability to persist in a difficult task, despite failure; capacity to delay reaction if easily frustrated, e.g., aggression, crying, tantrums, withdrawal, avoidance. G. Aggression: Modes of expression; degree of control of or preoccupation with aggression; appropriate assertiveness. 4. Motor Muscle tone and strength; mobility in different positions; unusual motor pattern, e.g., tics, seizure activity; intactness of cranial nerves, e.g., movement of face, mouth, tongue, and eyes, including feeding, swallowing, and gaze (Note excessive drooling.) A. Gross motor coordination Infants: Pushing up; head control; rolling; sitting; standing. Toddlers: Walking; running; jumping; climbing; hopping; kicking; throwing and catching a ball (It is useful to have something for child to climb on, such as a chair.) B. Fine motor coordination Infants: Grasping and releasing; transferring from hand to hand; using pincer grasp; banging; throwing. Toddlers: Using pincer grasp; stacking; scribbling; cutting. Both fine motor and visual-motor coordination can be screened by observing how child handles puzzles, shape boxes, a ball and hammer toy, small cars, and toys with connecting parts.
5. Speech and Language A. Vocalization and speech production: Quality, rate, rhythm, intonation, articulation, volume. B. Receptive language: Comprehension of others' speech as seen in verbal or behavioral response, e.g., follows commands; points in response to "where is" questions; understands prepositions and pronouns (Include estimate of hearing, especially in child with language delay, e.g., response to loud sounds and voice; ability to localize sound.) C. Expressive language: Level of complexity, e.g., vocalization, jargon, number of single words, short phrases, full sentences; over generalization, e.g., uses "kitty" to refer to all animals; pronoun use including reversal; echolalia, either immediate or delayed; unusual or bizarre verbalizations. Preverbal children: Communicative intent, e.g., vocalizations, babbling, imitation, gestures, such as head shaking and pointing; caregiver's ability to understand infant's communication; child's effectiveness in communication. 6. Thought The usual categories for thought disorder almost never apply in young children. Primary process thinking, as evidenced in verbalizations or play, is expected in this age group. The line between fantasy and reality is often blurred. Bizarre ideation; perseveration; apparent loose associations; and the persistence of pronoun reversals, jargon, and echolalia in an older toddler or preschooler may be noted in a variety of psychiatric disorders, including pervasive developmental disorders. A. Specific fears: Feared object; worry about being lost or separated from parent. B. Dreams and nightmares: Content is sometimes obtainable in children aged 2 to 3 years. Child does not always perceive it as a dream, e.g., "A monster came in the front door." C. Dissociative state: Sudden episodes of withdrawal and inattention; eyes glazed; "tuned out"; failure to track ongoing social interaction. Dissociative state may be difficult to differentiate from an absence seizure, depression, autism, or deafness. The context may be helpful, e.g., child with a history of neglect freezes in a dissociative state as mother leaves room. Neurologic or audiologic evaluation may be warranted. D. Hallucinations: Extremely rare, except in the context of a toxic or organic disorder, then usually visual or tactile. 7. Affect and Mood The assessment of mood and affect may be more difficult in young children because of limited language; lack of vocabulary for emotions; and use of withdrawal in response to a variety of emotions from shyness and boredom to anxiety and depression. A. Modes of expression: Facial; verbal; body tone and positioning. B. Range of expressed emotions: Affect, especially in parent-child relationship. C. Responsiveness: To situation; content of discussion; play; and interpersonal engagement. D. Duration of emotional state: Need history or multiple observations. E. Intensity of expressed emotions: Affect, especially in parent--child relationship. 8. Play Play is a primary mode of information gathering for all sections of the ITMSE. In very young children, play is especially useful in the evaluation of the child's cognitive and symbolic functioning, relatedness, and expression of affect. Themes of play are helpful in assessing older toddlers. The management and expression of aggression is assessed in play as in other areas of behavior. Play may be with toys or with child's own or another's body, e.g., peek-a-boo, roughhousing; verbal, e.g., sound imitation games between mother and infant; interactional or solitary. It is important to note how the child's play varies with different familiar caregivers and with parents versus the examiner. A. Structure of play (ages approximate) 1. Sensorimotor play a. (0-12 months): Mouthing, banging, dropping and throwing toys or other objects. b. (6-12 months): Exploring characteristics of objects, e.g., moving parts, poking, pulling. 2. Functional play a. (12 to 18 months): Child's use of objects shows understanding and exploration of their use or function, e.g., pushes car, touches comb to hair, puts telephone to ear. 3. Early symbolic play a. (18 months and older): Child pretends with increasing complexity; pretends with own body to eat or sleep, pretends with objects or other people, e.g., "feeds" mother; child uses one object to represent another, e.g., a block becomes a car; child pretends a sequence of activities, e.g., cooking and eating. 4. Complex symbolic play a. (30 months and older): Child plans and acts out dramatic play sequences, uses imaginary objects. Later, child incorporates others into play with assigned roles. 5. Imitation, turn-taking, and problem-solving as part of play. B. Content of Play The toddler's choice and use of toys often reflect emotional themes. It is desirable to have on hand toys that tap different developmental and emotional domains. An overfull playroom may be overwhelming or overstimulating and reduce meaningful observations. Young toddlers of both sexes often gravitate to dolls, dishes, animals, and moving toys, such as cars. The examiner's choice of specific materials may facilitate the expression of pertinent emotional themes. For example, a child traumatized by a dog bite may more likely reenact the trauma if a dog and doll figures are available. The child's reaction to scary toys, such as sharks, dinosaurs, or guns, should be noted, especially if they are avoided or dominate the session. Does aggressive pretend play become "real" and physically hurtful? By age 2½ to 3, a child's animal or doll play can reveal important themes about family life, including reactions to separation, parent--child and sibling relationships, experiences at day care, quality of nurturance and discipline, and physical or sexual abuse. The examiner must use caution in interpreting play, viewing it as a possible combination of reenactment, fears, and fantasy. 9. Cognition Using information from all above areas, especially play, verbal and symbolic functioning, and problem-solving, roughly assess child's cognitive level in terms of developmental intactness, delays or precocity. 10. Relatedness A. To parents: How "in tune" do the child and parent seem? Does the child make and maintain eye, verbal, or physical contact? Is there active avoidance by child? Note infant's level of comfort and relaxation being held, fed, "molding" into caregiver's body. Does toddler move away from caregiver and check back or bring toys to show, to put into his or her lap, to play with together or near caregiver? Comment on physical or verbal affection, hostility, reaction to separation and reunion, and use of transitional objects (blanket, toy, caregiver's possession). Describe differences in relating if more than one caregiver is present. B. To examiner: Young children normally show some hesitancy to engage with a stranger, especially after 6 to 8 months of age. Appropriate wariness in young children may result in a period of watching the examiner; staying physically close to a familiar caregiver before engaging; or showing some constriction of affect, vocalization or play. After initial wariness, does the child relate? Does the child engage too soon or not at all? How does relatedness with a stranger compare to that with a parent? Is the child friendly versus indiscriminately attention-seeking, guarded versus overanxious? Can examiner engage the child in play or structured activities to a degree not seen with caregiver? Does the child show pleasure in successes if the examiner shows approval? C. Attachment behaviors: Observe for showing affection, comfort-seeking, asking for and accepting help, cooperating, exploring, controlling behavior, and reunion responses. Describe age-related disturbances in these normative behaviors. Disturbances are often seen in abused and neglected children, e.g., fearfulness, clinginess, over compliance, hypervigilance, impulsive overactivity, and defiance; restricted or hyperactive and distractible exploratory behavior; and restricted or indiscriminate affection and comfort-seeking.
by Anne Benham, M.D.
REFERENCES
American Academy of Child and Adolescent Psychiatry (1997), Practice Parameters for the Psychiatric Assessment of Infants and Toddlers. J Am Acad Child Adolesc Psychiatry 36(10suppl)
American Psychiatric Association (1994), Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Washington, DC: American Psychiatric Press, Inc
National Center for Clinical Infant Programs (1994), Zero to three: Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood. Arlington, VA: Publisher
World Health Organization (1992), International Classification of Diseases, 10th Revision. Geneva: World Health Organization
