Co-variation of depressive mood and spontaneous physical activity evaluated by ecological momentary assessment in major depressive disorder

The objective evaluation of depressive mood is thought to be useful for the diagnosis and treatment of depressive disorders. Thus, we investigated psychobehavioral correlates, particularly the statistical associations between momentary depressive mood and behavioral dynamics measured objectively, in patients with major depressive disorder (MDD). Patients with MDD (n = 14) wore a watch-type computer device and rated their momentary symptoms using ecological momentary assessment. Spontaneous physical activity in daily life, referred to as locomotor activity, was also continuously measured by an activity monitor built into the device. A multilevel modeling approach was used to model the associations between changes in depressive mood scores and the local statistics of locomotor activity simultaneously measured. The statistical model constructed indicated that worsening of depressive mood was associated with increased intermittency of locomotor activity, as characterized by a lower mean and higher skewness. Our findings suggest the presence of associations between momentary depressive mood and behavioral dynamics in patients with depression, which may lead to the continuous monitoring of the pathological states of MDD.