Effects of carbamazepine vs valproate on cognitive functioning in patients with previously unmedicated epilepsy were evaluated in a prospective, randomized, double-blind Veterans Affairs multicenter study. Patients with seizures showed deficits relative to a normal control group prior to AED therapy. No significant decline from baseline levels of neuropsychological performance was detected over 6- or 12-month treatment intervals for either drug. Patients with high serum VPA levels (mean, 94 mcg/mL) performed less well than controls on measures of concentration and memory. Subtle compromises of cognitive functioning following treatment with VPA or CBZ were suggested by absence of practice effects. 
COMMENT. Carbamazepine and valproate monotherapies have subtle effects on cognitive functioning, when studies are well controlled.