The right side of the brain pertains to creativity, music, intuition, non-verbal memories, and spatial/social awareness. It’s the place in the brain where it sees the “big picture”. When it is overactivated, this is when your mind can go down a rabbit hole of “what if” type anxiety symptoms.
The left side of the brain pertains to logical thinking, math, problem solving, verbal memory, and language abilities. With depression there is typically a reward deficiency. This detail oriented side being so under activated and under rewarded is where symptoms of depression start to arise.