Low blood flow in the brain is linked to depression symptoms and severity

A study this year-- https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2832270--found that cerebral blood flow is linked to depression. It's not just a matter of neurotransmitter chemicals. 

This landmark research demonstrates that functional brain changes—specifically decreased blood flow—are more accurate markers of depression than structural brain changes like cortical thinning, which have historically shown weak and inconsistent associations. Amen Clinics provided one of the largest and most clinically detailed datasets for the study, drawn from patients actively seeking help for depression.

"This is the strongest evidence to date that depression is not just a chemical imbalance—it's a brain imbalance you can see and measure," said Dr. Daniel Amen, founder of Amen Clinics and a co-author of the study. "We've been saying for decades that healthy blood flow is foundational to mental health. Now the science has caught up."

https://www.prnewswire.com/news-releases/new-landmark-study-reveals-brain-blood-flow-as-key-biomarker-in-depressionamen-clinics-plays-pivotal-role-302422322.html

"This validates what we've seen in over 260,000 scans: depression often involves poor brain perfusion, and when we improve blood flow, people feel and function better," said Dr. Amen.

https://www.biospace.com/press-releases/new-landmark-study-reveals-brain-blood-flow-as-key-biomarker-in-depression-amen-clinics-plays-pivotal-role

That means exercise that gets blood moving really does play a role in helping us feel better emotionally. This insight is needed in our too-often sedentary society.