Psychomotor performance and monoamine function in bipolar and unipolar affective disorders

Affective disorders are associated with prominent psychomotor abnormalities that may be related to changes in arousal or motivation due to altered catecholamine function.

We investigated relationships between performance on psychomotor tests of motor speed (reaction time and tapping speed) and visual tracking (trail making and dot placement) and catecholamine system function including cerebrospinal fluid (CSF) or urinary concentrations of catecholamines or their metabolites. Subjects were medicine-free inpatients with unipolar depression or with manic, depressive, or mixed episodes of bipolar disorder, and healthy controls matched by gender and stratified by age.

Unipolar and bipolar depressed patients were impaired in motor speed, dexterity, and visual tracking, whereas manic and mixed patients did not differ from controls. Tapping speed correlated positively with CSF 3-methoxy-4-hydroxyphenylglycol in healthy controls and with CSF homovanillic acid in bipolar depressed subjects. Increased catecholamine function correlated with slowing in all other measures for patients with bipolar disorder. Relationships between catecholamines and psychomotor function were weaker in unipolar depressed subjects. Psychomotor function was related to severity of depression in bipolar, but not in unipolar, patients.

These data suggest that catecholamine systems are associated with increased arousal and psychomotor impairment in patients with bipolar disorder. Similar behavioral changes have different neurotransmitter relationships in unipolar disorder.