There is no question that PAE engenders the symptoms described in ND-PAE. The construction of these symptoms into a coherent neurobehavioral profile has been problematic, however. This study of ND-PAE criteria appears to be the first to utilize a prospective sample that integrates norm-referenced data with clinical interpretation of impairment and dysfunction in identification of symptoms. Consistent with previous research, results of this study continue to highlight the restrictive nature of the ND-PAE Adaptive Functioning domain. Apart from impairment in Daily Living Skills, impairment in Adaptive Functioning symptoms was relatively common (with Communication Deficit identified fourth most frequently overall and Social Communication and Interaction and Motor Skills tied for fifth). It is the organizational structure of ND-PAE and its domains, however that create restrictions on identification of impairment in Adaptive Functioning. Specifically, this requires endorsement of at least one of Communication Deficit or Social Communication and Interaction Impairment, and endorsement of a second symptom within the construct. Under these criteria, a patient without communication or social interaction impairments would not receive a diagnosis regardless of the neurocognitive, self-regulation, or adaptive functioning impairments that may be present. In essence, these criteria imply communication and social interaction as foundational characteristics of ND-PAE. This is problematic, however, because the PAE neurobehavioral profile is still in question [4] and these two areas of deficit have not been identified as foundational above other areas. Should the Adaptive Functioning domain and its symptoms remain intact, revisions to the number or types of symptoms for domain endorsement are needed.
Results of this study were mixed with regard to convergence of symptoms within domains. There was convergence between some symptoms under their shared domains (i.e. Global Intellectual Performance, Social Communication and Interaction), whereas other symptoms had associations with shared symptoms that were weak or absent (i.e. Executive Functioning, Learning). Internal consistency was acceptable for Neurocognitive and Adaptive Functioning domains but below the acceptable range in the case of Self-Regulation. Individual symptoms of Attention Deficit and Motor Skills adversely affected internal consistency within their respective domains. Likewise, results were mixed in assessing divergence between domains. Overall associations between domains themselves were relatively low suggesting divergence. There was, however, a considerable number of strong associations of symptoms across domains suggesting lack of divergence among symptoms.
There were some symptoms (Executive Functioning and Motor Skills) that were neither associated with symptoms within its shared domain nor other domains. Research has demonstrated clear evidence that PAE can result in Executive Functioning and Motor Skill deficits [20, 21], however, they may not be meaningfully categorized with other symptoms under a larger domain in a diagnostic model such as ND-PAE.
An exploratory factor analytic approach was undertaken to assess the factorial validity of ND-PAE. As such, results of the factor analysis should not be overestimated. These results, however, provide a glimpse into which symptoms may cluster similarly to, and differently from, ND-PAE domains, and provide means to assess relative contributions of symptoms within those factors (see Fig. 2).
Factor 1 consisted of symptoms from the Neurocognitive and Adaptive Functioning domains (Global Intellectual Performance, Executive Functioning, Memory, Visual-Spatial Reasoning, Social Communication and Interaction, and Daily Living Skills).
Adaptive behavior refers to skills needed to function effectively and independently for the self, in response to others, and in the larger social environment [22]. The construct of adaptive behavior developed in tandem with the construct of Intellectual Disability and is now integral in its diagnosis. The importance of adaptive behavior in this diagnosis is highlighted in that severity of Intellectual Disability is no longer defined by IQ score, but by degree of adaptive behavior deficits [14]. Definitions of adaptive behavior have developed over time based on assumptions of social competency and adjustment, adaptability to the environment, and managing everyday life demands. Research in the 1970s and 1980s identified common elements between its definitions and subsequent research examined the factor structure of adaptive behavior, consistently identifying four skill areas: conceptual, social, practical, and motor/physical competence. Contemporary assessment of adaptive behavior evaluates the first three domains, with evidence suggesting the motor/physical competence factor may not persist across the lifespan [23].
Various standardized interviews/questionnaires (i.e. VAB3, ABS, ABAS-3, SIB-R) are used to assess adaptive behavior under this general model consisting of conceptual, social, and practical skills. First, conceptual skills refer to competence in areas such as memory, language, problem solving, judgment, and time/money concepts. Second, social skills include interpersonal communication skills, social participation, social problem solving, and social reasoning. Third, the practical domain includes skills associated with health and safety, personal care, following routines, and maintaining household chores [14, 23]. The symptoms comprising Factor 1 appear to generally fit this conceptual (intellect/memory), social (social communication and interaction), and practical (daily living skills) model of adaptive behavior, though this hypothesis requires further validation.
Research has shown an association between PAE and adaptive behavior [24]. Adaptive behavior, adaptive skills, and adaptive functioning, however, has been integrated inconsistently between FASD diagnostic guidelines [7,8,9]. A standard definition of adaptive behavior is needed in the context of ND-PAE assessment, which should draw on adaptive behavior research already conducted over the past 50 years to lay its foundation rather than beginning anew.
Factor 2 consists of skills acquired through experience and learning. Communication deficits such as receptive or expressive language disorders are relatively common co-morbidities [25], as are learning disorders and deficits in academic achievement, mathematics in particular [15]. Caregiving environments for children with FASD may be variable and/or suboptimal [26], however, and can contribute to delays in development or academic skill acquisition, necessitating differential diagnosis [27]. Delays in academic skills may not manifest until adolescence as course content becomes more complex and classroom expectations increase. While the symptoms of Communication Deficit and Learning are well differentiated from other Factors and symptoms in this study, there is insufficient data to suggest they should be categorized as a stand-alone construct.
Factor 3 consists predominantly of Attention Deficit and Impulse Control, with relatively weak contribution of Motor Skills. Attention Deficit/Hyperactivity Disorder (ADHD) is frequently co-morbid with FASD [28]. These areas are often identified in clinical assessment even in the absence of other deficits. Research has shown neurocognitive differences between ADHD and FASD. For example, children with FASD show problems in underlying cognitive skills and more complex forms of attention (such as shift and encoding), whereas children with ADHD show greater difficulties with sustained and focused attention [29], and the severity of FASD tends to be greater than ADHD [30]. Factor 3 does not speak to external validity of ND-PAE, however, only that set of symptoms are differentiated from other sets of symptoms. Presence of ADHD symptoms may increase risk of false positive identification of ND-PAE and should be interpreted cautiously as central traits in clinical assessment (given that diagnoses of ADHD are relatively commonplace in some countries [31] and may be subject to increased probability of referral).
Factor 4 consists of a sole symptom, Mood and Behavioral Regulation. Many diagnostic systems for FASD do not include mental health assessment. While PAE may be a primary cause of mood and behavioral regulation problems, individuals with PAE at higher risk levels are more likely to experience a range of adversities that can also affect mental health [32].
Among these Factors, only Factors 1 and 2 were associated as clusters with FASD diagnosis. Further, symptoms of Executive Functioning and Motor Skills were weakly associated with their respective factors. While there is evidence from previous research that all ND-PAE symptoms can be adversely impacted by PAE, some areas such as Attention Deficit and Executive Functioning, may have weak differentiating power given that these problems may be commonly present in comorbid issues. Motor Skills shared relatively little association with other symptoms in this study, including those within its shared domain. There is considerable research, however, that PAE is associated with motor skill deficits [21, 33]. Continued assessment of motor skills is needed as it may identify functional impairment or serve as a neurological sign of adverse effects of PAE.
Recommendations
Future study of ND-PAE is needed and serves two important functions. First, this research can help to elucidate a coherent neurobehavioral profile caused by PAE. Much research to date has identified series’ of deficits associated with PAE [4, 29, 34, 35] but a specific neurobehavioral pattern or combination of symptoms caused by PAE that reliably distinguishes it from other conditions, should one exist, remains elusive. Unlike most mental disorders that are defined by its clusters of symptoms, ND-PAE, FASD, and the like are defined by its cause: PAE. Given the wide ranging effects of PAE on the central nervous system, plus the variable effects of dose, timing, and pattern of PAE, in addition to the compounding effects of other adverse prenatal and postnatal experiences [36], defining a clear neurobehavioral pattern of PAE is formidable. Future research on ND-PAE may clarify patterns of deficit that may lead to identification of central or distinguishing features that may be defined within our current conceptualizations of symptoms (which largely draws from individual standardized assessment) or other theoretical approaches to describing human behavior.
Second, an efficient, descriptive approach to screening and assessment is worth pursuing. FASD diagnosis over the past 20 years has increasingly emphasized the cognitive and behavioral deficits associated with PAE through comprehensive multidisciplinary team assessment [37]. Although this process continues to be important for accurate diagnosis, resource-efficient methods of identification and screening and, eventually, diagnosis are needed. Screening tools for FASD have been developed in the past [19, 38, 39] but this process requires further validation. In addition, a shared language is needed in order to provide equitable supports and treatment and to expedite research. ND-PAE, with its presence in an international taxonomy and its grounding in neurobehavioral evidence, provides opportunity to develop this approach.
Of the factors derived, impairment in Factors 1 and 2 were strongly associated with FASD diagnosis. These Factors should garner particular attention when further developing diagnostic criteria for ND-PAE, elucidating its behavioral patterns, and in constructing its neurobehavioral profile. Additional work is needed in distinguishing the central characteristics of PAE from those that cut across other disorders in order to ensure assessment approaches maintain high specificity. Notwithstanding, all symptoms are grounded in PAE research and could contribute to its diagnostic profile.
Limitations
The procedure to ND-PAE classification was non-blinded to clients and diagnosis and immediately followed a multidisciplinary assessment meeting where a different set of guidelines were used in determining an FASD diagnosis. Further, the approach is subject to acquiescence bias by clinic team members. There is limited generalizability given that this is a clinical sample from one FASD diagnostic clinic with little variation in team members from the onset of this study. There was low power given the relatively small sample size, therefore, factors derived should be used as a guidepost to future research and not the basis for clinical assessment. This sample does not include non-clinical participants exposed to PAE, however, ND-PAE and its criteria were under evaluation.
