Response to commentary on the multimodal treatment study of ADHD (MTA): mining the meaning of the MTA

In the December 2000 issue of the Journal of Abnormal Child Psychology, we published a set of papers presenting secondary analyses of the Multimodal Treatment Study of ADHD (MTA), and R. A. Barkley (2000) provided a commentary. A critique of the design of the study (MTA Cooperative Group, 1999) was presented based on a theoretical perspective of a behavioral inhibition deficit that has been hypothesized as the core deficit of ADHD (R. A. Barkley, 1997). The commentary questioned the design and analysis of the MTA in terms of (1) the empirical criteria for selection of components of behavioral (Beh) intervention, (2) the effectiveness of the Beh intervention, (3) the methods for analyses at the group and individual level, (4) implications of the MTA findings for clinical practice, (5) the role of genetics in response to treatment, and (6) the lack of a nontreatment control group. In this response, we relate the content of the papers to the commentary, (1) by reviewing the selection criteria for the Beh treatment, as outlined by K. C. Wells, W. E. Pelham, et al. (2000), (2) by addressing the myth that the MTA Beh treatment was ineffective (Pelham, 1999), (3) by describing the use of analyses at the level of the individual participant, as presented by J. S. March et al. (2000) and W. E. Pelham et al. (2000) as well as elsewhere by J. M. Swanson et al. (2001) and C. K. Conners et al. (2001), (4) by relating some of the suggestions from the secondary analyses about clinically relevant factors such as comorbidity (as presented by J. S. March et al., 2000) and family and parental characteristics (as presented by B. Hoza et al., 2000, S. P. Hinshaw et al., 2000, and K. C. Wells, J. N. Epstein, et al., 2000), (5) by discussing the statistical concept of heritability and the lack of a significant difference in the presence of ADHD symptoms in parents of the MTA families compared to parents in the classmate-control families (as presented by J. N. Epstein, et al., 2000), and (6) by acknowledging that an ethically necessary weakness of the MTA design is that it did not include a no-treatment control group. We discuss the use of secondary analyses to suggest how, when, and for what subgroups effectiveness of the Beh treatment may have been manifested. Finally, we invite others to use the large and rich data set that will soon be available in the public domain, to perform secondary analyses to mine the meaning of the MTA and to evaluate theories of ADHD and response to treatments.     

Personality and the genetic risk for alcohol dependence

The extent to which the genetic risk for alcohol dependence (AD) and conduct disorder (CD) and their common genetic risk overlap with genetic factors contributing to variation in dimensions of personality was examined in a study of 6,453 individuals from 3,383 adult male and female same-sex and unlike-sex twin pairs from the Australian Twin Registry. The associations between the personality dimensions of positive emotionality, negative emotionality, and AD and CD risk were modest, whereas the associations between behavioral undercontrol and AD and CD risk were substantially higher. Genetic influences contributing to variation in behavioral undercontrol accounted for about 40% of the genetic variation in AD and CD risk and about 90% of the common genetic risk for AD and CD. These results suggest that genetic factors contributing to variation in dimensions of personality, particularly behavioral undercontrol, account for a substantial proportion of the genetic diathesis for AD and most of the common genetic diathesis for AD and CD among both men and women.     

Neurophysiological markers of vulnerability to schizophrenia: sensitivity and specificity of specific quantitative eye movement measures

Eye-tracking deficits in schizophrenic patients and relatives have generated interest in using eye movements to mark schizophrenia liability. Efforts to develop specific quantitative measures have provided insight into the nature of the deficit and suggested what underlying neurophysiological mechanisms are involved. This study used receiver operating characteristic curve analyses to evaluate and compare the sensitivity, specificity, and overall accuracy of predicting disease liability using single and combined specific and global quantitative measures. Results indicate that measures of predictive pursuit and leading saccades significantly increased predictive accuracy compared with traditional global measures. Combining specific measures provided greater predictive accuracy compared with single measures. Implications for the use of specific eye movement measures to define schizophrenia-related phenotypes in genetic studies are discussed.     

Hand-scoring error rates in psychological testing

Despite the comprehensive treatment of test validity in most technical manuals, test authors appear to routinely assume that clients and professionals will score their instruments without error. Recently Allard and Faust challenged this assumption by suggesting that error rates "may not be rare or benign" and demonstrated that tests with more complex scoring procedures were associated with a greater number of scoring errors. This study investigated error rates that resulted from hand scoring seven psychometric tests commonly employed in psychological practice. Significant and serious error rates were identified for both psychologist and client scorers across all tests investigated. Scoring complexity was found to predict the base rate of scorer errors. The findings suggest that greater development in and attention to test-scoring procedures is required to restrict the likelihood of scorer error.     

Dyadic short forms of the Wechsler Adult Intelligence Scale-III

Various short forms of the Wechsler Adult Intelligence Scale (WAIS)/WAIS-R have been developed to obtain estimates of overall intellectual level, although little research of WAIS-III short forms has been published to date. Full Scale IQ (FSIQ) estimatesfromfour WAIS-III dyadic short forms were obtained by entering selected subtest scores from a mixed neurologic/ psychiatric sample (n = 196) into regression equations. Results were cross validated on a second sample (n = 57). Within both samples, WAIS-III FSIQ scores were highly correlated (r = .90-.92, p < .001) with estimated FSIQ scores. Estimated FSIQ fell within 5 points of actual FSIQ in 49% to 74% of cross-validation cases and within 10 points of actual FSIQ in 81% to 93% of the sample. Comparable to findings from previous short-form investigations, actual and estimated FSIQ classification levels agreed in 46% to 67% of cases in the cross-validation sample. These dyadic WAIS-III forms appear appropriate for obtaining gross estimates of FSIQ in similar populations, although caution is recommended in interpreting estimated IQ scores.