There's so many different kinds of depression (trauma, stress & chemical to list a few) & the appropriate diagnosis needs to be done to figure out treatment. More energy isn't a fix-it.
The form I'm familiar with is labeled clinical depression. It's electro-chemical. The example my MD gave me was that there are 3 brain chemicals in action when the synapses fire, transmit & receive. With the right med the brain fixes itself. If any of them aren't up to par then thinking is muddled & problematic because the juice isn't flowing & there's an equipment failure.
In my experience when the works are clogged i also get anxiety from fear. I have to back away & deal with the fear before i can deal with the clog, so i need space & time to find the brain's route around the blocked circuit. It's slow going.
The things I appreciate from people is patience & it helps when someone's willing to repeat the same thing 2-3 times without
. Don't try to "fix" someone's depression - it adds anxiety from failure to respond to good intentions. Acceptance (this is how it is for now) & reassurance (it's temporary) are welcome. And don't be afraid to say stop the pity party if you see your friend is self-absorbed. It helps break the cycle.
Best wishes to you both.