Monoamine hypothesis

The Monoamine Hypothesis suggests that depression is linked to imbalances in certain brain chemicals called monoamines—mainly serotonin, norepinephrine, and dopamine. These chemicals help regulate mood, motivation, and emotional well-being. When their levels are too low or their function is impaired, it can contribute to feelings of sadness, hopelessness, and other depression symptoms. Many antidepressant medications work by increasing the availability of these chemicals in the brain, aiming to restore balance and improve mood. This hypothesis has guided much of depression treatment, though ongoing research continues to deepen our understanding of the condition.