The results of a recent study (see reference below) indicate that the severity of psychotic depression (PD) can be divided into the following categories based on the PDAS totalscore:

Remission of PD: PDAS totalscore <8

Mild PD: PDAS totalscore from 8 to 15

Moderate PD: PDAS totalscore from 16 to 23

Severe PD: PDAS totalscore >23

Reference: Ostergaard SD, Rothschild AJ, Flint AJ, Mulsant BH, Whyte EM, Vermeulen T, Bech P, Meyers BS. 2015. Establishing the cut-off score for remission and severity-ranges on the Psychotic Depression Assessment Scale (PDAS). J Affect Disord. http://www.ncbi.nlm.nih.gov/pubmed/26496016