Clock Drawing Test in patients with schizophrenia

Abstract 

Investigations of the usefulness of the Clock Drawing Test (CDT) in schizophrenia have focused primarily on institutionalized or elderly patients. The purpose of the present study was to compare CDT performance of patients with schizophrenia living in the community with that of normal controls. Fifty-three patients with schizophrenia were compared with 66 age- and gender-matched normal controls. The CDT (‘free-drawn’, ‘pre-drawn’ and three ‘examiner’ conditions) and the Mini-Mental State Examination (MMSE) were administered to all participants. In patients with schizophrenia, symptom severity was assessed with the Positive and Negative Syndrome Scale (PANSS). Patients with schizophrenia had significantly lower scores on the MMSE and the five CDT conditions than the control group. When MMSE scores and level of education were included in the comparisons as covariates, the differences between the two groups remained significant. MMSE scores of the patients with schizophrenia correlated significantly with four clock conditions: ‘free-drawn’ ‘pre-drawn’ and two of the ‘examiner’ conditions (11:10 and 8:20). Poorer performance on the CDT correlated with higher scores on the PANSS positive symptoms subscale. Qualitative analysis of the clocks that were drawn revealed specific errors in the schizophrenia group relating to frontal processes: difficulty placing numbers in the correct position, failure to indicate the minute targets, displacement of the minute hand from the minute number, and failure to draw a longer minute hand. The fact that the CDT is sensitive enough to detect the cognitive impairment inherent in schizophrenia, as well as being correlated with symptom severity, makes this test useful in roughly assessing cognitive state in schizophrenia.

Keywords: Clock drawing test, Schizophrenia, Cognition, Neuropsychology