Processing speed and its influence on psychometric intelligence in adolescents suffering from Multiple Sclerosis

Processing speed (PS) is frequently reduced in adult and adolescent patients suffering from Multiple Sclerosis (MS). Reduced PS also leads to impaired working memory in adult MS patients. Less is known about the interplay of cognitive deficits in adolescent MS patients. In the present study, therefore, we investigated whether PS is reduced in adolescent MS patients compared to healthy controls (HC) and whether reduced PS might explain potential differences in psychometric intelligence between MS patients and HC. Twenty-one adolescent MS patients and 21 HC completed a reaction time (RT) task and Cattell’s Culture-Fair-Test (CFT 20-R). MS patients had slower RT and lower intelligence scores than HC. An analysis of covariance revealed that group differences in intelligence could be completely explained by PS differences. The results support DeLuca et al.’s (2004) relative consequence model of cognitive deficits in MS stating that slower PS leads to impaired higher-order information processing.