56 Studies on the objective assessment of these features in relation to circadian rhythms have contributed to the understanding of the pathophysiology of affective illnesses. In the next section we discuss the psychomotor activity studies in affective disorder patients. Actigraphy studies Psychomotor activity and its temporal rhythms provide valuable,

quantitative and objective find more assessments of psychiatric patients, particularly with affective or attentional disorders.57,58 Such activity Inhibitors,research,lifescience,medical is conveniently recorded with wrist-worn piezoelectric actigraphic devices with microprocessors that provide objective, quantitative evaluation of motility levels and their Inhibitors,research,lifescience,medical dynamic changes over several days. Actigraphy also distinguishes sleep from waking, and can indicate specific sleep phases.57,59-62 Analyses of activity data document a substantial phaseadvance (earlier daily peak [acrophase]) of circadian activity cycles in bipolar disorder (BPD) patients,63,64 in contrast to a more likely phase-delay

(later acrophase) in unipolar major depressive disorder (MDD),65 seasonal affective disorder (SAD),66 Inhibitors,research,lifescience,medical and winter depression in BPD with seasonal pattern.57 Circadian activity phase-delay, estimated crudely with daily sleep logs and self-reports Inhibitors,research,lifescience,medical of morning versus evening activity levels, was associated with low winter mood in the general population and SAD patients.67-69 Circadian phase variation was addressed indirectly by evaluating a measure

based on individual preference for activities in the morning versus evening in BPD patients, who differed significantly from controls and schizophrenia or schizoaffective, patient-subjects.70 The preference of BPD patients for “eveningness” Inhibitors,research,lifescience,medical (including delayed sleep timing and difficult morning awakening) rather than “morningness” suggests a rather stable chronotype. However, this chronotype varies somewhat seasonally and with shorter light cycle duration during fall-winter phases.39 Actigraphy has also documented reduced total activity56,71-73 and blunted daily activity-amplitude in MDD subjects,74 nearly sometimes with circadian phase advances in subjects with endogenous depression.75 Such alterations have been particularly striking among subjects diagnosed with bipolar disorder during mania, depression, or shortly before or after acute episodes of illness, as well as in mild or subsyndromal morbid phases.76-82 Some changes persist after clinical recovery from depression or mania, and so may serve as biomarkers of stable traits, and not only as covariates of current mood states.