Method Review _1
Miranda Palmer Psychopharmacology May 16, 2004 Brief Written Abstract Article: Latent Class and Factor Analysis of DSM-IV ADHD: A Twin Study of Female Adolescents Factor analysis was used to determine whether the DSM-IV subtypes of inattention, hyperactivity, and combined type are appropriate. The computer program SAS was used to perform the factor analysis on data from the 1549 twin pairs. The researchers than used the computer program to perform an oblique promax rotation on the resulting factors. Two, three and four factor extractions were performed, however three or more factors did not lead to separate hyperactive and inattentive factors. The researchers concluded that two factors were appropriate, correlated at 0.51 best described as an inattention factor and a hyperactivity factor. Inattention Factor produced loadings of inattentive items ranged from .57 to .79 with low loadings, those below .017, in respect to hyperactive items. Hyperactivity factor had loadings of .55 to .63 regarding hyperactive items, with loadings below 0.14 on inattentive items. Factor analysis was an appropriate statistical analysis because the researchers wanted to find out if the psychological constructs being currently used to identify subtypes of ADHD were supported by data. Furthermore, the data set was numerical and included two or more variables. The researchers concluded that the factor analysis supported the current ADHD types of inattentive, hyperactive-impulsive, and combined type. This conclusion supported previous studies, and was also supported by additional analysis performed by this study’s researchers. Additionally, the researchers concluded that ADHD is undertreated and because behavioral symptoms yielded a 9.9% prevalence of ADHD in this sample of twin girls. Researches cited limitations of the study as maternal report, delayed reporting, single reporting source, biased gender sample, and a lack of consideration of comorbid conditions. Depression, anxiety disorders, and other behavior disorders are highly comorbid with ADHD. Furthermore, a diagnosis of ADHD requires that symptoms not occur primarily in the course of another axis I disorder. Additional limitations include that the researchers did not justify the reason for using a oblique rotation. Furthermore, it is concerning that the researchers had such a strong idea about how many factor would be a good fit before data exploration. Although the conclusions drawn regarding the factors relating to ADHD were not overstated, the clinical recommendations were. Recommendations based on the 9.9% prevalence rate found in the sample of girls. However, no discussion regarding the need to rule out other diagnosis before an accurate diagnosis was made.