Is psychotic depression a mental illness?

The term psychotic depression is not a primary diagnosis but is widely used to describe Major Depression with psychotic features*. The psychotic features may be delusions or hallucinations. The condition is a diagnostic subtype of depression, therefore classed as a mood disorder and is not related to an underlying psychosis.

It is a “mental illness” to the same extent as major depression... Largely dependent on your understanding of the term.

*Diagnostic and Statistical Manual (DSM-IV-TR, Sec. 296.24 and 296.34) Is also applicable to bipolar disorder.

Yes phsycotic depression

Found this on another site: Psychotic major depression (PMD) is a type of depression that can include symptoms and treatments that are different from those of non-psychotic major depressive disorder. Many people with psychotic depression experience delusions, which are beliefs or feelings that are untrue or unsupported. PMD is sometimes mistaken for NPMD, schizoaffective disorder, schizophrenia or other psychotic disorders. Bipolar patients may experience PMD during depressed states. PMD is usually episodic, lasting for a defined amount of time, but in some cases can be chronic. PMD has unique biological features, which have led to innovative treatments. While PMD is often treated with a combination of antidepressants and antipsychotics, researchers have been developing new treatments that address the pathophysiology of PMD more directly.

So I think it is but you would have to get the evaluation from a psychologist.