Speech as an objective measure of psychomotor dysfunction in major depressive disorder: validation from non-speech motor measures.

Psychomotor dysfunction, which can manifest as slowing (psychomotor retardation; PmR) and jerkiness or restlessness (psychomotor agitation; PmA) often occurs in individuals with major depressive disorder (MDD). As psychomotor dysfunction predicts a worse treatment response, accurately measuring and tracking PmR and PmA may improve outcomes. Traditionally, psychomotor dysfunction has been assessed using self-report or observer-based methods, which are often insensitive to subtle but potentially relevant movement abnormalities. Instrumental probes often require specialized equipment. Speech presents a promising option as it requires a significant motor component and is easy to collect. This study serves as a preliminary test of the association between speech indicators of PmR and PmA and manual motor tasks (handwriting velocity and force variability). Participants with current MDD (n = 36) and remitted MDD (n = 78) completed a diadochokinetic speech task, quickly repeating syllables in a sequence ("pataka" and "katapa"), as well as a test of handwriting velocity while drawing loops (PmR) and a test of variability in force applied to a transducer (PmA). Velocity of speech production and speech rate variability were automatically measured. For current MDD individuals, speech velocity was positively associated with the manual PmR measure (t(29) = 2.59, p < 0.05), and speech rate variability was positively associated with the manual PmA measure (t(33) = 2.952, p < 0.01). Effects were not significant for remitted MDD individuals, suggesting that this method may detect PmR/PmA only in those with acute depressive symptoms. These results suggest that diadochokinetic speech is a promising, objective measure of psychomotor dysfunction.