I was particularly excited to sit down with one of my long term colleagues, psychiatrist Dr. James Greenblatt for an exploration of his new book "Finally Hopeful subtitle". Dr. Greenblatt is one of the pioneers of functional and integrative psychiatry, and it's his fourth interview with the MindHealth360 Show. His first three were about suicide, ADHD and Eating Disorders. This one was about the biological root causes of depression – and why identifying them could fundamentally change the way we diagnose and treat mental illness.
Dr. Greenblatt argues that depression is not one uniform condition: ten people with the same diagnosis may have ten different underlying drivers. From vitamin D and B12 deficiencies, amino acids, thyroid and hormone imbalances, to low cholesterol, impaired digestion and chronic infections, he explains why common and measurable biological factors can contribute to depressive symptoms – and why testing for root causes should often come before treatment.
But this is not a conversation about replacing antidepressants with supplements. Dr. Greenblatt is equally critical of functional medicine approaches that focus on tests and large supplement protocols without understanding the individual patient. We explore his mantra to "treat patients, not tests", and examine why trauma and chronic stress can impair digestion and nutrient absorption, and why nervous-system regulation, and an understanding of psycho-social factors and relationships must sit alongside biochemical treatment.
In this episode, you'll learn:
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Why ten people with depression may have ten completely different underlying causes.
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Why clinicians should investigate factors including thyroid function, iron, B12, zinc and vitamin D before automatically reaching for an antidepressant.
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Why vitamin D deficiency is associated with depression, anxiety and suicide risk – and why testing matters more than simply giving everyone vitamin D.
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How trauma and chronic stress can suppress stomach acid and digestion, leaving people low in amino acids even when they eat adequate protein.
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Why commonly accepted B12 "normal" ranges may miss deficiencies relevant to brain and mental health.
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Why very low cholesterol levels may be an overlooked biological factor in depression, addiction and suicide risk.
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What new research tells us about lithium orotate and brain health, and why lithium is being reconsidered by mainstream psychiatry.
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Why "treat patients, not tests" has become one of Dr. Greenblatt's central principles – and why more supplements do not necessarily mean better treatment.
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Why he considers somatic therapies particularly important for patients whose stress and trauma are held in the body.
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Why ketogenic diets and psychedelics can be powerful tools, but may still become sophisticated "Band-Aids" if basic biological deficiencies are overlooked.
Take the conversation further at IMMH 2026
At this year's Integrative Medicine for Mental Health (IMMH) Conference, Dr. James Greenblatt will take several of the ideas explored in this episode into greater clinical depth across two sessions:
Amino Acids as Precursors for Neurotransmitters – exploring how amino acid deficiencies can affect neurotransmitter production, and how targeted testing and repletion may support more personalised approaches to depression.
Functional Medicine for Obsessive Compulsive Disorder – examining evidence-based nutritional approaches to OCD, including inositol, NAC and 5-HTP, alongside nutrigenomic testing to inform individualised treatment.
Join Dr. Greenblatt and more than 50 leading clinicians, researchers and thought leaders at IMMH 2026, October 8–11 in San Diego.
Early Bird ticket prices – available until August 31
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In-person ticket: $1,045
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Virtual ticket: $495
Get tickets here: https://www.immh.org/immh-2026/
