ISTDP Hub · Research
The Evidence Base for ISTDP
ISTDP has a larger and more rigorous body of evidence than most psychodynamic approaches. The findings are particularly strong in the areas where other therapies most often fall short.
How the Evidence Compares
ISTDP sits within the experiential-dynamic tradition, which has historically been under-researched compared to CBT. Over the past two decades that has changed significantly. The approach now has multiple RCTs, systematic reviews, and meta-analyses — across a range of clinical presentations.
A 2012 meta-analysis published in the Harvard Review of Psychiatry (Abbass et al.) reviewed 33 studies and over 2,000 patients. The findings showed large effect sizes for depression, anxiety, and somatic disorders — with effects maintained and sometimes increased at follow-up. This is unusual in the psychotherapy literature.
Key Studies in Plain Language
Meta-Analysis · 2012
Abbass, Town & Driessen — Harvard Review of Psychiatry
The most-cited ISTDP meta-analysis. 33 controlled studies, 2,173 patients. Large effect sizes for depression, anxiety, somatic disorders, and medically unexplained symptoms. Effects maintained or increased at follow-up — suggesting continued processing after therapy ends.
Read the study →RCT · Treatment-Resistant Depression
Abbass et al. — ISTDP for Treatment-Resistant Depression
In the Halifax Depression Study, a randomized controlled trial of 60 patients with treatment-resistant depression, those who received ISTDP showed significantly greater symptom reduction than usual care (Cohen's d of 0.75-0.85 on depression measures), with 36% reaching remission at 6 months compared with 3.7% in the usual-care group. The findings support ISTDP as a credible option for complex and treatment-resistant presentations rather than a last resort.
Read the study →Meta-Analysis · Medically Unexplained Symptoms
Short-Term Psychodynamic Therapy for Functional Somatic Disorders
A 2020 meta-analysis of randomized controlled trials found that short-term psychodynamic approaches (of which ISTDP is a leading model) reduced unexplained physical symptoms — including fibromyalgia, chronic pain, and IBS — consistent with the model's account of how anxiety reroutes into the body when emotional processing is blocked.
Read the study →Cost-Effectiveness · Healthcare Systems
Reduced Healthcare Utilization After ISTDP
Follow-up data from the Halifax Depression Study and an independent tertiary-care cost study found that ISTDP reduced healthcare utilization in the Canadian system significantly — with an average reduction of over $12,000 in healthcare costs per case over 3 years, and fewer GP visits, specialist referrals, and medication use after treatment. The approach tends to be cost-effective precisely because it works at the level of underlying cause rather than symptom management.
Read the study →Online Delivery · What the Evidence Actually Shows
ISTDP Online vs In-Person — A Mixed Picture, Honestly Reported
We want to represent this evidence accurately rather than overstate it. The one randomized controlled trial directly comparing the two (for patients with medically unexplained pain) found that in-person ISTDP produced significantly better outcomes than internet-delivered ISTDP on pain, depression, anxiety and emotion regulation, both immediately after treatment and at 12-month follow-up. Online delivery still has real value — it remains credible and engaging to patients, and is often the only realistic option for those outside a therapist's city — but for this specific presentation, in-person delivery currently has the stronger evidence.
Read the study →The evidence base for online ISTDP is still developing. Many patients find online sessions effective and convenient, and it is often the most realistic option for those outside a therapist's city — even where in-person delivery currently has a stronger evidence base for specific presentations.
Online Sessions →The ISTDP Evidence in Context
ISTDP is not the best-evidenced therapy for every presentation. Where it stands apart is in complex, chronic, and treatment-resistant cases — the patients most likely to have tried other approaches and found them insufficient. For these presentations, the evidence is genuinely strong.
If you want to read more, Allan Abbass's book Reaching Through Resistance provides both the clinical framework and the evidence base in accessible form. It is listed on the reading page.
Explore the ISTDP Hub
Each part of the ISTDP framework connects to the others. These pages take the next step.
Anxiety
Understand Your Anxiety Pathway
Anxiety in ISTDP is a signal, not a disorder. It always points toward something — a feeling that hasn't reached awareness yet. This page maps the three distinct ways anxiety discharges through the body, and includes an interactive tool to help you identify which pathway is most active for you.
Explore anxiety →Defenses
Recognise Your Defense Mechanisms
Defenses are intelligent strategies — built in childhood, still running in adulthood. They keep the anxiety manageable and the feelings at bay. But they come at a cost. This page explains the ten most common patterns and includes a self-reflection quiz to help you spot which ones dominate for you.
Explore defenses →Emotions
Why Feelings Matter — Core Emotions Wheel
Anxiety is always a response to a feeling that hasn't surfaced. But what exactly is a core feeling, and how do you distinguish it from a thought, a mood, or a narrative? This page introduces the primary emotional landscape, with an interactive wheel of core emotions and a plain explanation of why access to them — not just understanding — is what produces change.
Explore emotions →Attachment
Your Attachment Style and the Patterns It Created
The anxiety-defense pattern you carry today was built inside your earliest relationships. Depending on how caregivers responded to your feelings, you developed a characteristic way of managing closeness and emotional expression. This page explains the four attachment styles and includes a self-reflection tool to help identify which patterns feel familiar.
Explore attachment →Ready to Try What the Evidence Supports?
The research is one part of the picture. The other is your own experience of what's been missing. A first session brings both together.
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