I thought getting the black dog is getting down for a period of time ( not depression - certainly not as serious as that)
However, its used by some mental health groups in a metaphorical sort of way - The term describes a state of depression characterized by sadness or lack of will, including the loss of desire to partake in activities you once loved. This metaphor can be helpful for adults and children living with depression and those with loved ones experiencing symptoms. The image of a large, intrusive black dog may more clearly identify the often difficult-to-see aspects of depression. (that bit comes from the betterhelp web site )
...on the other hand
The wikipedia bit ....The Black Dog is a supernatural or demonic hellhound originating from English folklore, and also present in folklore throughout Europe and the Americas. It is usually unnaturally large with glowing red or yellow eyes, is often connected with the Devil (as an English incarnation of the hellhound), and is sometimes an omen of death. It is sometimes associated with electrical storms(such as Black Shuck's appearance at Bungay, Suffolk). and also with crossroads, barrows(as a type of fairy hound), places of executionand ancient pathways.
Black dogs are generally regarded as sinister or malevolent, and a few (such as the Barghestand Shuck) are said to be directly harmful.Some black dogs, however, such as the Gurt Dog in Somerset, are said to behave benevolently as guardian black dogs, guiding travellers at night onto the right path or protecting them from danger.The black dog is a recognised folkloric motif.
,, and finally . We have just got a black puppy ( with two white paws and a white chest - OK not really a black dog) .. and he's not depressed at all , ever ,,, he'll lick you to death if gets a chance. I may have mentioned him before - he's called Woody.
This is a re-mix of a tune from November 2023.
