Background. Motor slowing in depression may be associated with a relative dopaminergic (DA)
deficit. Bradykinesia in Parkinson's syndrome is associated with an abnormally short silent period
(SP) using transcranial magnetic stimulation (TMS). We hypothesized that depression would also
be associated with a short SP.
Methods. Sixteen patients with DSM-IV depression and 19 matched controls participated. SPs were
elicited by exercising the contralateral abductor policis brevis (APB) during TMS.
Results. The SP was significantly increased in the patient group. No correlation was found between
SP and depression score.
Conclusion. A long SP suggests increased motor cortical inhibition in depression. This finding is
inconsistent with the hypothesis of behavioural motor slowing in depression being associated with
Parkinsonian-like mechanisms including the dopaminergic deficit. There is a need for studies
incorporating larger patient groups to investigate potential correlations between SP and depression