Actigraphic registration of motor activity reveals a more structured behavioural pattern in schizophrenia than in major depression

Motor activity was recorded using wrist-worn actigraphs for periods of 2 weeks in patients with schizophrenia and major depression and compare them to healthy controls. Average motor activity was recorded and three non-parametric variables, interdaily stability (IS), intradaily variability (IV), and relative amplitude (RA) were calculated on the basis of these data. The motor activity was significantly lower both in patients with schizophrenia (153 ± 61, mean ± SD, p < 0.001) and depression (187 ± 84, p < 0.001), compared to controls (286 ± 80). The schizophrenic patients had higher IS and lower IV than the controls reflecting a more structured behavioural pattern. This pattern was particularly obvious in schizophrenic patients treated with clozapine and was not found in depressed patients.Motor activity was significantly reduced in both schizophrenic and depressed patients. However, schizophrenic patients differed from both depressed patients and controls, demonstrating motor activity patterns marked by less complexity and more structured behaviour. These findings may indicate that disturbances in motor activity reflect different pathophysiological mechanisms in schizophrenia compared to major depression.Assessing motor activity is essential in every psychiatric evaluation. Despite this, objective methods are rarely used in psychiatric clinical practice.It is well known that increased or decreased gross motor activity is often seen in patients with schizophrenia [1]. Altered motor activity is also an integral part of the clinical picture of depressive states [2], and is seen in seasonal affective disorder [3] and major depression in children and adolescents [4]. Depressed patients differ from normal and psychiatric comparison groups with regard to objectively quantified gross motor activity, body movements, speech, and motor reaction time [5]. Psychomotor retardation during depression may be measured by actigraph [2]. In major depressive disorder hypofrontality and