Communication, specifically the elements crucial for normal social interaction, can be significantly affected in psychiatric illness, especially depression. Of specific importance are prosody (an aspect of speech that carries emotional valence) and formulaic language (non-novel linguistic segments that are prevalent in naturalistic conversation). The goal of this study was to examine elements of prosody (through acoustic analysis and listener perceptions) and formulaic language in the naturalistic, conversational speech of individuals with treatment-resistant depression pre- and post-deep brain stimulation of the subcallosal cingulate white matter. In support of the literature, prosodic elements were reduced in depression as measured acoustically and via listener perception. Listeners distinguished healthy adults from those with depression and rated persons with depression as sounding more sad and bored. Listeners perceived differences in pre- and post-operative prosody, but acoustic measures did not detect these. There were fewer conversational speech formulas produced for those with depression. More non-nuanced formulas were produced post-operatively. This study provided insight into the importance of listener perceptions in prosody research, a first look at the production of formulaic language in depression, and a foundation for further study into the pragmatic components of communication, to address the often-reported diminished social connectedness in depression. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]