The link between depression and performance on the Symbol Digit Modalities Test: Mechanisms and clinical significance

Abstract

Objective:

To determine the mechanism and clinical significance of depression-related differences in performance on the Symbol Digit Modalities Test (SDMT).

Methods:

The influence of depression on two versions of a computerized SDMT (i.e. fixed versus variable code) was assessed. Both versions involve processing speed, but the fixed c-SDMT also encompasses incidental visual memory.

Results:

Depression was associated with a 19.06% slowing on the variable (p = 0.002) and an 8.10% slowing on the fixed (p = 0.219) c-SDMT.

Conclusion:

Depression-associated differences in performance on the SDMT appear linked more to a reduction in processing speed than a decline in incidental visual memory and exceed the 10% threshold considered clinically significant.

Keywords

Multiple sclerosis depression cognition

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