 of development underlie working hypotheses about the sources of challenging behaviors and how these may represent manifestations of various mental disorders. This system is less often applied and often less useful in the presence of severe IDD, cerebral palsy, epilepsy and other neurological, genetic disorders (including recognizable behavioral phenotypes) (7, 15).
In the final analysis, it is a combination of these models with behavioral and neuropsychological data that help us integrate biology, past life experiences and psychological development into our understanding of aggression, self-injurious behavior (SIB), hyperactivity and stereotypies. The increased use of attachment and separation-individuation models are providing additional insights into how an individual with IDD adapts and responds to his psychosocial environment (16). In addition, ethology, neuro-ethology and behavioral pharmacology are becoming useful tools in understanding complex social behaviors such as aggression or avoidance behaviors. This information may be as valuable as measured intellectual abilities in explaining what initiates and maintains these behaviors.
Deficits in adaptive skills are more than meets the eye
Adaptive skills represent an amalgam of abilities associated with 1) behavioral flexibility, 2) experiential learning (“plastic” intelligence), 3) problem solving, 4) coping with novel settings 5) task demands (procedural learning) and 6) mastery of skills of daily living. Social intelligence is another subset of adaptive skills that do not seem directly tied to other forms of intelligence but play a key role in all forms of skill learning (14). This relative disconnect reinforces the importance of adaptive skills in the definition of IDD.
For example, individuals with mild IDD may have sufficient adaptive skills to “disappear” into the workday world after completing school. In general, their cognitive limitations are camouflaged by good communication and reasonable adaptive skills. Yet abuse/neglect, coexisting developmental disorders (e.g., autism spectrum disorder or cerebral palsy) and mental disorders can derail this more favorable developmental trajectory (15). From a neuropsychological perspective, early environmental insults can adversely affect behavior regulation, cognitive flexibility, stress management as well as lower the threshold for major mental disorders. For many supportive caregivers, positive learning experiences and the availability and utilization of individually-directed and designed programs can compensate for these psychosocial insults and improve outcome by enhancing resilience and coping skills.
Individuals with severe-profound IDD (SPIDD) present a different picture. These individuals may lack the intellectual or adaptive capacities to deal with many routine life experiences. The increased prevalence of genetic, neurological, medical and other developmental disorders limit the pace of learning and can produce less reversible ceiling effects on adaptive skills (15, 17). Yet individuals with SPIDD are more likely to respond to physiological and psychological distress by increases in the frequency or severity of either pre-existing or new patterns of challenging behaviors (baseline exaggeration). For example, changes in expected routine or caregiver can be highly stressful events. Because of limited communication skills, challenging behaviors become the primary mode of expressing distress or pain. Understanding and interpreting these behavioral responses can require a combination of provider familiarity and clinical savvy.
Problems arise when clinicians misattribute these transient or environmentally driven changes in behavior (baseline exaggerations, behavioral regression and cognitive disorganization) as a primary neuropsychiatric disorder. The reverse can also be true: the emergence of a primary psychiatric disorder may increase the individual’s vulnerability to that stress or be the cause of the reaction. Impaired adaptive skills can become a setting event, contributing factor, or an impediment to the n