Deficit in verbal learning in schizotypal personality disorder

Abstract

Further study of neuropsychological function in schizotypal personality disorder (SPD) is important for advancing our understanding of the cognitive and clinical features of SPD and its relationship to schizophrenia (SZ). The few studies of neuropsychological function in schizotypy (nunpsychotic individuals thought to be vulnerable to SZ) have suggested deficits similar to, but less severe than, those found in SZ. However, in previous studies, subjects generally have not met full diagnostic criteria for SPD, and few neuropsychological measures have been employed, so that the nature of cognitive dysfunction in SPD remains unclear. In the current study, we examined a wide array of neuropsychological functions in ! ! right-handed males who met DSM-lli-R criteria for SPD and ! 1 right-handed male control subjects. Functions measured included abstraction, verbal and spatial intelligence, memory and learning, language, attention, and motor skills. Compared to controls, SPD subjects showed a striking decrement in performance on the California Verbal Learning Test (CVLT), a word-list learning measure which requires clustering for more effic~,e,~g performance. This deficit was seen against a background of relatively normal performance, and was nearly as severe as those of many schizophrenic samples reported in the literature. SPDs also showed a reduction in performance on the Wisconsin Card Sort Test (WCST), a measure requiting concept formation, abstraction and mental flexibility. The results suggest neuropsychological dysfunction in SPD, and are consistent with current hypotheses of left-temporal and prefrontal brain dysfunction in SZ. Consistently, preliminary MRI data from one SPD subject showed evidence of structural abnormalities in medial temporal lobe regions. sary to reach the conventional SP of 0.80 was very high 1.6. Lower ES such as 0.5 or 1.0 resulted in unacceptably low SP of 0.14, and 0.45 respectively. The number of subjects required to achieve a SP of 0.80 with ES of 0.5 or 1.0 were 93 and 25 respectively. Even if each of the studies reviewed here had tested only one hypothesis then in order to achieve a SP of 0.80 the ES should have been at least 1.0. In conclusion, given their design, most studies reviewed here could identify only very large effect sizes. For the identification of moderate treatment effect sizes (F.S-0.5) much larger numbers of subjects would be necessary. Even limitation to one single hypothesis per study would not ensure satisfactory power with these sample sizes.