as well as availability and adequate resources for staff and educators. Finally, limitations on funding and access to an integrated system of comprehensive health and mental health care (26) are present in many states. The care of high service users such as those with dual diagnosis is especially vulnerable to these socio-political forces (8, 27–29). This unfortunate scenario may underlie the recent trends toward increasing use of psychotropic drugs (30, 31).
It is also important to recognize a selection bias inherent in most mental health referrals. Since referrals arise due to disruptive, destructive, self-injurious behaviors or irritable/aggressive behaviors we must maintain a high index of suspicion for unrecognized psychiatric or medical/neurological disorders. Sorting out these generic referrals is the function of differential diagnosis. The following steps are useful in this process:
Data collection and decision making: Collect medical, psychiatric and developmental histories—both indirect reports and direct observations—and data from available rating scales. Convert this information into a timeline to create a visual representation of behavioral or symptom change through time. Converting behavioral information into a graphic format permits the clinician to track both behavioral data but also to integrate syndrome change (e.g. bipolar disorder); severity and intensity measures; and findings from serial mental status and rating scales. The Assessment of Dual Diagnosis (ADD) (32), the Emotional Problems Scale: Behavior Ratings Scale (EPS-R) (33) and The Diagnostic Assessment for the Severely Handicapped-II (34) are informant–based rating scales that cross-walk with the DSM-IV TR. The ADD and EPS-R were developed for patients with mild to moderate IDD whereas the DASH-II was developed for patients with SPIDD. Treatment response can also fit into this scheme (15).
Management of medical/neurological and laboratory data: Include and integrate relevant baseline medical studies, available information on genetic and metabolic disorders, neurophysiological and neuroimaging studies. These data need to be formulated for each phase of this outline for differential diagnosis. Clinical screening and neuropsychological testing are useful when dementia is suspected (35, 36).
Integrate medical/psychiatric assessment with functional behavioral analysis: Missing from many functional behavioral analyses are information about temperament, level of emotional reactivity, neuroticism, patterns of attachment, preponderance of approach/avoidance behaviors, emotional regulation, and level of impulse control. These neurobiological traits can profoundly influence a patient’s vulnerability to specific antecedents or triggers (8). For example, individuals with a history of severe abuse may be hypersensitive to being left alone at night, or attempts to set limits (18, 37, 38). This data may help explain what appears to be a persistent, disproportionate and treatment resistant reaction. A similar expanded mode of analysis involves both motivational and sustaining factors. For example, state-related anhedonia in major depression can reduce the reinforcement efficacy of social contact or favored activity (39). Likewise negative emotional reactions to novel situations or new staff or fear noted above should determine the pace of changes in behavioral programming (35, 37, 40, 41).
Social context of behaviors: Aggression (42), self-injury and other target behaviors occur in a social context. For many patients with SPIDD, aggression or SIB can represent forms of social communication (43) or expressions of attachment, dominance and territorial disputes (e.g. whose chair is this?). Psychiatric disorders also occur within and affect social networks, families, school and in work settings. Formulating this data may be more useful than a simple Axis V number in treatment planning (8, 44).
The last step is developing a multiaxial, psychiatric diagnosis. In the past there was difficulty matching the patient to the diagnostic criteria that were not adapted to th