ObjectivesBipolar and unipolar depressions have a similar clinical picture, but different neurological and psychological mechanisms. These misleading similarities can lead to overdiagnosis and increased suicide risk. Recent studies show that gait is a sensitive objective marker for distinguishing the type of depression. The present study aims to compare psychomotor reactivity disorders and gait activity in unipolar and bipolar depression.MethodsA total of 636 people aged 40.7 ± 11.2 years are studied with an ultrasound cranio-corpo-graph. They are divided into three groups - patients with unipolar depression, with bipolar depression and healthy controls. Each person performs three psychomotor tasks - a classic Unterberger task, a simplified version with open eyes and a complex version with an additional cognitive task.ResultsWe find significant differences in psychomotor activity and reactivity between the three groups. Bipolar patients have more inhibited psychomotor skills than unipolar and they are both more inhibited than the norms. The simplified variant of the equilibriometric task is the most sensitive one and psychomotor reactivity is a more precise marker than psychomotor activity.ConclusionBoth psychomotor activity and reactivity in gait could be sensitive markers for distinguishing similar psychiatric conditions. The application of the cranio-corpo-graph and the possible development of similar devices could lead to new diagnostic and therapeutic approaches, including early detection and prediction of the type of depression.