Naga Venkatesha Murthy, P.J., Gangadhar, B.N., Janakiramaiah, N., Subbakrishna, D.K. (1997). Normalization of P300 Amplitude following Treatment in Dysthymia. Biological Psychiatry, 42, 740-743. 

Studies in major depression have revealed “state” dependent smaller amplitude of P300 event related potential (ERP) (Blackwood et al 1987; Gangadhar et al 1993). Whether it is true in dysthymia remains untested. In the study by Shagass et al (1985), neurotic patients were vaguely assumed to have a dysthymic disorder and the study included evoked potentials but not cognitive ERPs. Giese-Davis and Miller (1987) studied mismatched negativity in dysthymics (DYs), whereas Yee and Miller (1988) studied the emotional information processing with respect to modulation of fear, and did not address the P300 ERP abnormalities per se in DYs. Likewise, Yee et al (1992) have studied in DYs ERP components earlier to P300. Bruder et al (1995) found reduced amplitude and hemispheric asymmetry of P300, using dichotic complex tone test, in 44 depressives (five DYs dysthymics). In the present study we compared the P300 ERP in DYs, depressives with melancholic features (DMs), normal controls, and included a follow-up to examine if P300 abnormalities persist upon improvement.