So, it is not quite like learning that the sun is not carried on the back of a turtle but seeing the sun continue to rise, but it is similar.
Over the years patients have come to me saying they think they have or have been told they have a chemical imbalance of neurotransmitters. I would try not to roll my eyes but when really irritated I would ask which neurotransmitter was out of balance and how was it measured. In reality, it was a metaphor and not a biological assay, and although they did not know the details of how this worked, it at least gave it a medical, biological reason they were depressed instead of it being due to poor choices and moral ineptitude. They were referring to what is called the serotonin hypothesis of depression that has been around for 50 years based on the observation that when medications, like the old antihypertensive medicine reserpine, depleted amines in the brain, depression ensued. Later, tricyclic antidepressants and monoamine oxidase inhibitors were found to increase the effects of serotonin and other monoamines in the space where two cells communicate, the synapse, and the theory has been that depression can be caused by a decrease in serotonin and depression can be treated by medicines that increase serotonin.