Cognitive disorders are now considered a core feature of the clinical picture of depression 

” In the past, little or no attention was paid to cognitive disorders associated with depression (a condition sometimes termed pseudodementia)………...It is now recognized, on the basis of observations and scientific evidence, that cognitive disorders are a core feature of the clinical picture of depression and should not be considered merely secondary to it; moreover, they are among the main causes of functional impairment in depressed patients. Cognitive symptoms should therefore be regarded as a partially independent dimension of MDD, and an important target of any treatment that is initiated ……………………………………………………………………….

……….Differential diagnosis: the neurologist’s perspective

In clinical practice, it is extremely difficult to distinguish, early on, between cognitive impairment (degenerative or vascular) that is destined to advance and depression-related cognitive impairment that can be reversed. Although various features have been identified to help support this differential diagnostic process (Table 1), on their own they are insufficient. ……….

Table 1

Anamnestic and clinical features distinguishing dementia from cognitive impairment associated with major depressive disorder (MDD) (“pseudodementia”)

Dementia	Cognitive impairment associated with MDD
Gradual onset	Sudden onset
Slow progression	Rapid progression
Patient has no insight	Patient has insight
Confabulations	Memory disorders
Patient minimizes the impairment	Patient emphasizes the impairment
Behavior consistent with the extent of the impairment	Behavior often inconsistent with the extent of the impairment
Frequent failure to respond	Non-specific answers (eg, “I don’t know”)
Nocturnal exacerbation of symptoms	No nocturnal changes
Incongruous mood	Depressed mood
Rare vegetative symptoms	Frequent vegetative symptoms
Infrequent previous psychiatric history	Frequent previous psychiatric history
Low risk of suicide	High risk of suicide

Cognitive impairment in depression: recent advances and novel treatments Giulia Perini,^1,2Matteo Cotta Ramusino,^1,2Elena Sinforiani,¹Sara Bernini,¹Roberto Petrachi,³ and  Alfredo Costa^1,2 Neuropsychiatr Dis Treat. 2019; 15: 1249–1258. Published online 2019 May 10. doi: 10.2147/NDT.S199746

The research on the cognitive impairment of major or bipolar depressive disorders [and of mania] is just beginning.

I hope that …to be continued…