In this Substack post, Dr. Martin Picard lays out the conceptual groundwork for understanding mental illness as a disorder of cellular energy metabolism rather than solely a problem of neurotransmitters or psychology. Drawing on his work in mitochondrial biology and psychobiology, Picard explains how brain function, mood, and behavior are inseparable from how cells generate, distribute, and regulate energy. He connects stress, inflammation, trauma, and environmental inputs to metabolic signaling pathways—particularly those involving mitochondria—that shape neural function over time. The post does not argue a specific treatment or intervention, but instead provides a unifying framework that helps explain why mental illness so often overlaps with metabolic, inflammatory, and systemic disease.