Understanding Depression in 2026: From Symptoms to Precision Psychiatry

By Joao L. de Quevedo, MD, PhD, Director, Center for Interventional Psychiatry UTHealth Houston
May 4, 2026

photos of a man sitting with his head down in sadness

Why We Still Don’t Fully Understand Depression

Depression is one of the most common and disabling conditions worldwide—affecting approximately one in six individuals over a lifetime. Yet despite decades of research, it remains one of the most complex and heterogeneous disorders in medicine.

A newly released volume, Understanding Depression: Contemporary Issues and Dilemmas (Second Edition), brings together global experts to address one central question:

Why is depression so difficult to diagnose, understand, and treat effectively?

I had the privilege of contributing to this work alongside international collaborators, reflecting a shared effort to rethink how we conceptualize and treat this condition.

The Problem: One Diagnosis, Many Diseases

Current diagnostic systems, such as DSM-5, rely on symptom clusters.

  • Patients need 5 out of 9 symptoms
  • There are over 200 possible symptom combinations

This means that two patients with the same diagnosis may have very different underlying biology

This heterogeneity is not just theoretical—it has real consequences:

  • Variable treatment response
  • High rates of treatment resistance
  • Difficulty predicting outcomes

Beyond Symptoms: A Biological Perspective

The book highlights that depression is not a single disorder, but rather a collection of biologically distinct conditions.

Key systems involved include:

  • Neurotransmitter dysfunction
  • Brain circuit abnormalities
  • Neuroendocrine stress responses
  • Chronic inflammation

In fact:

Up to 30% of patients show neuroinflammatory abnormalities, which may explain poor response to standard treatments

The Rise of Precision Psychiatry

A central theme of the book is the shift toward precision psychiatry:

Moving from “trial-and-error” treatment
Toward biologically informed, individualized care

This approach integrates:

  • Genetics
  • Biomarkers
  • Neuroimaging
  • Clinical phenotypes

Emerging research has already identified:

Multiple biological subtypes of depression, each with distinct symptoms and treatment responses

The Role of Environment and Epigenetics

Depression does not arise from biology alone.

It reflects a dynamic interaction between:

  • Genetic vulnerability
  • Environmental stress
  • Early-life experiences

Epigenetics provides a powerful framework to understand this interaction:

How life experiences can modify gene expression without changing DNA

This helps explain:

  • Why trauma increases depression risk
  • Why individuals respond differently to stress

Treatment: Where We Are—and Where We Are Going

Despite advances, approximately:

30% of patients remain treatment-resistant

However, the therapeutic landscape is rapidly evolving.

Current and Emerging Options:

  • Antidepressants
  • Esketamine (SPRAVATO®)
  • Transcranial Magnetic Stimulation (TMS)
  • Electroconvulsive Therapy (ECT)
  • Vagus Nerve Stimulation (VNS)

Future directions include:

  • Psychedelic therapies
  • Glutamate-based treatments
  • Biomarker-guided interventions

A Critical Insight: Rapid-Acting Treatments

One of the most important advances discussed is the emergence of rapid-acting therapies, particularly ketamine.

These treatments:

  • Target glutamate pathways
  • Enhance neuroplasticity
  • Can reduce symptoms within hours to days

This represents a paradigm shift—especially for patients with severe or suicidal depression

UTHealth Houston Perspective

At the Center for Interventional Psychiatry at UTHealth Houston, our approach reflects many of the principles outlined in this book:

  • Treating depression as a biologically complex condition
  • Integrating interventional therapies early when appropriate
  • Moving toward personalized treatment strategies

Our goal is to bridge:

Science → Clinical care → Real-world outcomes

The Bigger Message

This book reinforces a critical shift in psychiatry:

Depression is not a single disease—it is a spectrum of disorders with distinct biological drivers

And with that comes a new responsibility:

  • To improve diagnostic precision
  • To tailor treatments
  • To move beyond symptom-based frameworks

Final Thoughts

We are entering a new era in psychiatry.

An era where:

  • Biology informs diagnosis
  • Data guides treatment
  • Patients receive more precise, effective care

But we are not there yet.

The challenge ahead is not just scientific—it is clinical, educational, and systemic.

Understanding depression is no longer just about identifying symptoms.

It is about decoding complexity—and translating it into better care

Reference

Kim Y-K (Ed.). Understanding Depression: Contemporary Issues and Dilemmas (Second Edition).
Advances in Experimental Medicine and Biology, Vol. 1502. Springer, 2026.

Contact

Request for Second Opinion Form – https://Go.uth.edu/CIPIntake (external link)
Phone – (713) 486-2621
Fax – (713) 500-2728
E-mail – [email protected]
Website – https://go.uth.edu/CIP (external link)

Disclaimer

This article was created with the assistance of artificial intelligence (AI) to help organize and refine the presentation of scientific information. All medical and scientific content has been reviewed and approved by Joao L. de Quevedo, MD, PhD, Executive Director of the Center for Interventional Psychiatry at the John S. Dunn Behavioral Sciences Center at UTHealth Houston. The content is intended for educational and informational purposes only and does not substitute for professional medical advice.