Depression often demonstrates itself in the cognitive profile with lower Performance than Verbal IQs (Gregory, 1987; Zimmerman & Woo-Sam, 1973). The reason for the higher Verbal IQ is generally believed to be due to impaired concentration, psychomotor retardation, anxiety, or low motivation. Indeed, some of the diagnostic signs of depression besides those of depressed mood include psychomotor retardation, fatigue, and diminished ability to concentrate or think (American Psychiatric Association, 1994). The size of the V-P pattern has not been consistent in the literature. This V > P pattern may be small, such as the 2.3-point difference on the WAIS for 21 patients with depression studied by Loro and Woodward (1976) or the 3.8-point difference on the WAIS-R for a sample of 62 adult patients with depression (Bornstein, Termeer, Longbrack, Heger, & North, 1989). However, it may average more than 15 points, as it did for Pernicano's (1986) sample of 12 male veterans hospitalized for depression who were administered the WAIS-R.
In a sample of unmedicated, medically healthy, middle-aged to elderly outpatients diagnosed with mild to moderate major depression, Boone et al. (1994) found a V > P pattern for three age groups from 46 to 85 years. Specifically, patients with depression ages 46-59 (N = 36), ages 60-69 (N = 23), and ages 70-85 (N = 14) were contrasted with patients who were not depressed in the same age range (Ns = 58, 54, and 41, respectively). All of the depressed samples showed a mean V > P pattern, with discrepancies of 3.3, 7.6, and 4.1 points, for the three respective age groups. The youngest two groups of controls (ages 46-59 and 60-69) also showed a V > P pattern, with discrepancies of 2.7 and 1.9 points, respectively. However, the 70 to 85-year-old controls showed the opposite pattern of P > V (3.3 points). Overall, the mean V > P difference for the depressed sample was 5 points and the corresponding difference for the controls was 0.5 points, which generally supports the association that is posited between depression and high Verbal IQ.
Inpatients and outpatients with bipolar disorder have also been shown to obtain a V > P pattern on the Wechsler tests (Hoff et al., 1990; Nair, Muller, Gutbrodt, Buffet, & Schwartz, 1979). A sample of 35 inpatients with bipolar disorder (46% male; mean age = 36.5 years; 29% not medicated, 71% on lithium or another medication) obtained a 5.8-point V > P profile (Hoff et al., 1990). Additionally, a sample of 21 outpatients with bipolar disorder (38% male, mean age = 50), all on lithium therapy, obtained an 11-point V > P profile (WAIS V-IQ = 97.7 and P-IQ = 86.9; Nair et al., 1979). The sample's worst performance was in Digit Symbol, although the most interesting finding was the significant negative correlation between Performance IQ and duration of lithium therapy (r = -.52). The lowest P-IQs were earned by patients with bipolar disorder who had been on lithium therapy for the longest time. Those on lithium for the longest time also tended to be characterized by mental slowness. This slowness, rather than diminished accuracy, may account for the depressed P-IQ (Judd, Hubbard, Janowsky, Huey, & Takashi, 1977). Nonetheless, evidence from animal behavior studies (Johnson & Barker, 1972) suggests that lithium's effects may emerge by "impairing central analysis of stimulus input whereby significance is attached to sensory information" (p. 666). Consistent with both proposed explanations are the significant negative correlations between length of lithium therapy and the success of patients with bipolar disorder on Picture Arrangement and Digit Symbol (Nair et al., 1979).
Because of the various hypotheses advanced for the relatively low P-IQs of patients with depression and bipolar disorder, for example, psychomotor retardation, fatigue, and mental slowness, the WAIS-III factor index profile on these samples of patients will be especially interesting to evaluate. Of particular interest will be the relationship of POI to PSI, and the relationship of each of these nonverbal scales to VCI.
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