No psychomotor slowing in fine motor tasks in dysthymia

Few studies using objective and sensitive measuring techniques have investigated whether psychomotor retardation (PR), an important symptom of a major depressive disorder (MDD), is also present in dysthymic patients. In this study, the following questions were addressed: (1) is PR also prevalent in dysthymia? (2) If so, is the PR cognitive or motor in nature? And (3) does the nature and degree of the PR in patients with dysthymia differ from the PR in MDD patients found in earlier studies?

PR was measured by comparing the, digitally recorded, fine motor performance of 20 unmedicated dysthymic inpatients (mean age: 33) and 32 controls on copying and drawing tasks. In addition, the performance of the dysthymic patients was compared to the performance results of 32 unmedicated MDD inpatients collected in an earlier study.

The dysthymic patients were not slower than the controls in performing the fine motor tasks: neither initiation time (IT) nor movement time (MT) were prolonged. As expected, the MDD patients did show significantly longer ITs and MTs in all tasks compared to the controls. On the clinical Salpetriere Retardation Rating Scale (SRRS), the dysthymic patients had high scores on mainly subjective cognitive items like concentration and memory complaints.

The dysthymic patients had significantly less severe forms of depression compared to the MDD patients. As dysthymia, by definition, is a less severe form of depression we could not examine whether PR would manifest itself in severely depressed dysthymic patients, as is the case in certain MDD patients.

In this study, no objective evidence was found for PR in dysthymic patients during fine motor tasks. PR may be used to differentiate between dysthymia and MDD.