Comparative neurocognitive effects of 5 psychotropic anticonvulsants and lithium

Many of the new antiepileptic drugs have psychiatric indications, and most are prescribed by psychiatrists for patients with mood disorders, even when a specific indication is absent. Epileptic drugs as a whole, even the newer ones, are known to affect cognition, sometimes in untoward ways. Research on the neurocognitive effects of antiepileptic drugs, however, has been done exclusively in normal volunteers and in patients with seizure disorders.

A naturalistic, cross-sectional study was conducted on patients who were taking 1 of 5 different antiepileptic drugs or lithium (LIT). Cognitive status was measured by a computerized neurocognitive screening battery, CNS Vital Signs (CNSVS).

One hundred fifty-nine patients with bipolar disorder, aged 18-70 years, were treated with carbamazepine (CBZ) (N = 16), lamotrigine (LMTG) (N = 38), oxcarbazepine (OCBZ) (N = 19), topiramate (TPM) (N = 19), and valproic acid (VPA) (N = 37); 30 bipolar patients were treated with LIT.

Significant group differences were detected in tests of memory, psychomotor speed, processing speed, reaction time, cognitive flexibility, and attention. Rank-order analysis indicated superiority for LMTG (1.8) followed by OCBZ (2.1), LIT(3.3), TPM (4.3), VPA (4.5), and CBZ (5.0).

The relative neurocognitive effects of the various psychotropic antiepileptic drugs in patients with bipolar disorder were concordant with those described in the seminal literature in normal volunteers and patients with epilepsy. LMTG and OCBZ had the least neurotoxicity, and TPM, VPA, and CBZ had the most. LIT effects on neurocognition were intermediate. Choosing a mood-stabilizing drug with minimal neurocognitive effects may enhance patient compliance over the long term.