This is nonsense. I mean, it makes sense if you want to analyze it logically. Vit D deficiency (ergo-cholecalciferal) creates muscle and bone weakness in adults and rickets in infants. Dealing with ongoing pain and fractures because of the deficiency makes one be more depressed. So the assumption may be correct but the above “evidence” is quite scant.
Bump
I say this is just the reason we needed to run around naked in the sunlight.
“Moreover, poor vitamin D status causes an increase in serum parathyroid hormone levels.” Overactive parathyroid glands are frequently accompanied by symptoms of depression that disappear after treatment of the condition.”
Makes sense to me.