The overwhelming consensus is that depression arises because of something called the monoamine hypothesis. That is, people with depression have a shortage of two particular chemicals, serotonin and norepinephrine. Therefore, it makes sense that the vast majority of treatment options focus on fixing this imbalance.
The problem is that it doesn't always work.
"Thirty percent of people on these drugs do not experience an effect," Yumiko Saito and Yuki Kobayashi, neuroscientists at HU’s Graduate School of Integrated Arts and Sciences, said in a statement.
"Obviously, we need a new drug! We need another explanation for what could cause depression."
And that is what they have found. The results of a new study have been published in the journal Neuroscience.
It comes down to a very specific protein called RGS8, which is involved in movement and mood regulation and is responsible for controlling the hormone receptor MCHR1. When MCHR1 is active and working as it should, it helps regulate sleep, feeding, and emotional responses.
Previous studies have suggested that low levels of RGS8 can increase depressive behavior but until now, this theory has not been tested on living organisms. So the researchers had mice complete a forced swim test, which is a method often used to test depressive behavior in animals. They worked out each critter's total immobility time, ie the amount of time they spent not swimming.