Ketamine fades within days. A week of magnetic stimulation may hold it longer
STUDY: Su TP et al, Psychiatry and Clinical Neurosciences 2026
STUDY TYPE: Randomized, double-blind, sham-controlled trial
FUNDING: Kun-Po Soo Medical Foundation, Taiwan Ministry of Science and Technology
Background
Ketamine relieves treatment-resistant depression within hours, but relief usually fades in 3 to 14 days. Intermittent theta burst stimulation (iTBS), a form of transcranial magnetic stimulation (TMS) that delivers the magnetic pulse over a few minutes, may extend ketamine’s brief window of brain plasticity.
This study tested iTBS as a twice daily treatment for 5 days, delivered after response to two ketamine infusions in unipolar and bipolar depression.
The Study
- 45 adults in Taiwan with treatment-resistant unipolar or bipolar depression who responded to two ketamine infusions (0.5 mg/kg) in one week.
- 38 responders were randomized to active or sham iTBS over the left prefrontal cortex, twice daily for 5 days; 37 completed follow-up.
- The main outcome was change on the Depression scale (MADRS) through day 49.
Results
The active group had lower depression scores across follow-up, a small-to-moderate effect. The difference narrowed by weeks 6 and 7.
Remission rates were higher with active iTBS:
- Day 15: 87% versus 50%.
- Day 29: 81% versus 46%.
Patients on sham were more likely to lose their response (HR 4.18), though the survival curves didn’t clearly separate. Suicidal thoughts fell during ketamine and stayed low in both groups.
Side Effects
Some patients needed lower stimulation intensity because of scalp pain.
Limitations
- Small sample, and the remission comparisons weren’t planned in advance.
Practice Implications
- The idea makes biological sense, but this trial is small and preliminary.
- Psychotherapy is another way to extend ketamine’s benefits.
—Chris Aiken, MD
Director, Psych Partners
Editor in Chief, Carlat Psychiatry Report
