Behavioral Studies of Mental Retardation and Depression
William McIlvane

Funded by NICHD, R01 HD42807

It is increasingly being recognized that people with mental retardation may be prone to neuropsychiatric problems. Yet to be determined, however, is the degree to which all of the criteria specified in the DSM-IV for various disorders can be effectively operationalized for this population. The focus of the proposed project is clinical depression in people with mental retardation and limited language. Certain hallmarks of depression (changes in body weight, sleep problems, psychomotor agitation, etc.) can be detected readily via conventional observation techniques. However, other hallmarks (e.g., diminished motivation, behavioral impersistence, etc.) are less readily and reliably operationalized because (1) people with significant mental retardation cannot participate meaningfully in clinical interviews and (2) third-party reports (i.e., from normally capable informants) may be of questionable value in this case. To operationalize DSM-IV criteria pertinent to these more difficult constructs, we propose to adapt state-of-the-art behavioral testing methods developed under past NICHD sponsorship. Our working hypothesis is that such methods can be used to inform us about the cognitive functioning of persons with and without a clinical dual diagnosis of mental retardation and depression; specifically, we predict that persons with depression and mental retardation will perform less optimally on tests of attention, memory, executive functioning, behavioral momentum, and reinforcer sensitivity than comparable individuals without depression.

Should our hypothesis be confirmed, the results would demonstrate the feasibility of operationalizing DSM-IV criteria for laboratory study of persons with severe mental retardation and limited language. Screening necessary to pursue our primary objective and other methodological development efforts will have two secondary benefits. Our project will produce (1) data that may be useful in assessing the degree to which a major depressive disorder may limit inclusion possibilities and (2) methods that may prove useful for more sensitive assessment of the effects of pharmacological intervention and for ultimate study of the target population via bioimaging methods.