Lithium and Valproate May Affect Motor and Sensory Speed in Patients with Bipolar Disorder

Objective: Although many studies have found a negative effect of lithium (Li) on the motor system in bipolar disorder, there is a lack of evidence about the effects of valproate (VP) on motor and sensory speed. We aimed to compare the effects of Li and VP on motor and sensory speed in medication-free bipolar patients (MF) and healthy controls (HCs). Methods: Euthymic patients with bipolar disorder according to the DSM-IV on Li monotherapy (n=22), VP monotherapy (n=21), MF (n=18) and HCs (n=37) were enrolled. The finger-tapping test, Pegboard Test, visual and auditory reaction time tests, Montreal Cognitive Assessment and Edinburgh Handedness Inventory were the measures. Results: The Li group was significantly slower than the HC and MF groups in the right hand trial of the Pegboard Test. The Li group scored significantly lower in the right and left hand trials of the finger-tapping test in comparison to the HC and MF groups. All patient groups (MF, Li and VP) had slower visual reaction time scores than the HC group. The Li and VP groups had significantly slower auditory reaction time scores than the HC group. Conclusion: Lithium may impair sensory and motor speed more than VP. Medication-free patients differed from healthy controls only in the visual reaction time test. Lithium may disturb movement systems by affecting the complex integration of the brain structures serving motor coordination. These results may also suggest that in the euthymic phase of bipolar disorder, disturbance of psychomotor functions may be related to medications.