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Objectives: A vast amount of studies demonstrates the presence of psychomotor slowing in schizophrenia. The objective of the present study was to investigate whether this overall psychomotor slowing can be divided into distinct processes that differentially affect cognitive functioning in schizophrenia., Methods: The pen-tip movements of 30 schizophrenic inpatients and 30 matched controls were digitally recorded during performance of the Symbol Digit Substitution Test (SDST) and analysed to differentiate matching time and writing time, representing the cognitive and sensorimotor component of slowing, respectively. In addition, the results were compared to each other and to the scores of traditional neuropsychological tests that assess domains such as memory and attention., Results: Both matching time and writing time were longer in the schizophrenic patients relative to the controls but did not correlate. Only matching time correlated significantly with the conventional neuropsychological test results., Conclusions: Although schizophrenic patients display both sensorimotor and cognitive slowing, the two processes are unrelated. Furthermore, only the cognitive component was associated with most of the cognitive deficits as measured by traditional neuropsychological tests.

Few studies examining psychomotor retardation (PR) in patients with major depressive disorder (MDD) included medication-free patients. The purpose of this study was (1) to examine whether unmedicated patients with MDD would exhibit PR, (2) to determine whether this retardation, if present, was more cognitive or motor in nature, and (3) to investigate whether any differences in PR could be established between melancholic and nonmelancholic depressed patients. Thirty-eight unmedicated inpatients with severe MDD (20 melancholic and 18 nonmelancholic patients) and 38 matched controls were compared on figure-copying tasks in which the cognitive task difficulty was manipulated. In addition, a simple motor task and the symbol digit substitution task (SDST) were administered. As a group, the patients were significantly slower performing all tasks and both initiation times (IT) and movement times (MT) were prolonged. However, when a distinction was made between the two subtypes, only the melancholic patients showed prolonged MTs compared to the controls. Furthermore, the melancholic patients differed significantly from the controls in IT in all tasks. The nonmelancholic patients had significantly longer ITs than the controls in two copying tasks. It can be concluded that there was clear cognitive and motor slowing in this group of unmedicated inpatients with MDD. The melancholic patients were more severely affected than the nonmelancholic patients and showed a slowing of cognitive as well as motor processes. Differences in psychomotor functioning between melancholic and nonmelancholic depressed patients could imply different underlying neurobiological disturbances in these subtypes of major depression.

Schizophrenia and depression have an overlap in symptomatology, namely a slowing in both motor and mental activities, denoted in depression as 'psychomotor retardation' and in schizophrenia as 'psychomotor poverty'. By means of a new technique that allows the measurement of psychomotor speed and the computerized analysis of writing movements recorded during the performance of the Digit Symbol Test, it indeed proved to be possible to observe a slowing in both disorders. In addition, a different structure of slowing in the two patient groups could be identified.