A pooled analysis of 4,056 participants from the SURMOUNT weight loss trials found tirzepatide did not increase depression or suicidal ideation compared to placebo — and depression scores actually improved slightly more with the drug.
Depression scores lower with tirzepatide (p < 0.001)After 72 weeks, tirzepatide-treated participants had a PHQ-9 score of 1.9 vs. 2.4 for placebo, and were significantly less likely to shift to a more severe depression category (18.2% vs. 24.3%).
What the researchers found
In 4,056 adults with obesity and no known major psychopathology from the SURMOUNT trials, tirzepatide was not associated with increased depression risk compared to placebo. At week 72, tirzepatide-treated participants had significantly lower PHQ-9 depression scores (1.9 vs. 2.4; treatment difference -0.6; p < 0.001) and were less likely to shift to a more severe depression category (18.2% vs. 24.3%; p < 0.001). Suicidal ideation was reported by 0.6% in both groups, and suicidal behavior (nonfatal) occurred in 0.1% on tirzepatide vs. 0% on placebo. Psychiatric adverse events were similar between groups.
Why it matters
With tirzepatide rapidly becoming one of the most widely prescribed weight loss drugs worldwide, understanding its psychiatric safety profile is critical. Regulatory agencies and the public have raised concerns about potential links between incretin-based therapies and depression or suicidality. This large-scale analysis from three pivotal trials provides reassuring evidence that tirzepatide does not increase depression risk — and may even slightly improve depressive symptoms — in people without pre-existing psychiatric conditions.
How the study worked
Post hoc analysis pooling data from three SURMOUNT clinical trials (SURMOUNT-1, -2, -3). Participants (N = 4,056) with overweight/obesity and no known major psychopathology received tirzepatide (5/10/15 mg or maximum tolerated dose) or placebo. Depression was measured using the Patient Health Questionnaire-9 (PHQ-9) and suicidal ideation/behavior using the Columbia-Suicide Severity Rating Scale (C-SSRS) over 72 weeks. Adverse events related to nervous system and psychiatric disorders were also collected.
Who was studied
4,056 adults with overweight/obesity and no known major psychopathology from the SURMOUNT-1, -2, and -3 clinical trials
What this study cannot tell us
This is a post hoc analysis, not a prospectively designed psychiatric safety study. Participants with known major psychopathology were excluded from the SURMOUNT trials, so results cannot be generalized to people with depression, bipolar disorder, or other psychiatric conditions. The 0.1% suicidal behavior rate in the tirzepatide group (vs. 0% placebo) is based on very small numbers and cannot be conclusively interpreted. Follow-up was limited to 72 weeks.
How to read the evidence
This is a post hoc analysis of three large, double-blind, placebo-controlled randomized trials (SURMOUNT-1, -2, -3). While the SURMOUNT trials are high-quality RCTs, the psychiatric analysis was not the primary endpoint, and the exclusion of participants with major psychopathology limits generalizability. Post hoc analyses are considered hypothesis-generating rather than definitive.
When this study was published
Published in 2026, this is extremely current and directly addresses ongoing safety concerns about tirzepatide and mental health that are actively debated by regulators and the public.
The bigger picture
This analysis addresses one of the most pressing safety questions in the GLP-1/GIP agonist era: do these drugs cause psychiatric harm? Combined with recent systematic reviews finding no confirmed causal link between incretin-based therapies and suicidality, this data strengthens the case that tirzepatide is psychiatrically safe in people without pre-existing mental illness. However, the field recognizes that the millions of people now taking these drugs include many with psychiatric comorbidities who were excluded from these trials.
Questions still open
- Is the slight improvement in depression scores with tirzepatide a direct pharmacological effect, or is it secondary to weight loss and improved quality of life?
- What is the psychiatric safety profile of tirzepatide in people with pre-existing depression, anxiety, or other major psychiatric conditions?
- Do the very low rates of suicidal behavior (0.1% vs. 0%) become more meaningful with larger sample sizes and longer follow-up?
Common questions
Can tirzepatide (Mounjaro/Zepbound) cause depression or suicidal thoughts?
Why did depression scores actually improve with tirzepatide?
Read the original research
Psychiatric Safety of Tirzepatide in People With Obesity and No Known Major Psychopathology: A Post Hoc Analysis of SURMOUNT.
Obesity (Silver Spring, Md.), 34(3), 565-578
Citation
Wadden, Thomas A; Oquendo, Maria A; Kushner, Robert F; Cao, Dachuang; Karanikas, Chrisanthi A; Kechter, Afton; Murphy, Madhumita A. (2026). Psychiatric Safety of Tirzepatide in People With Obesity and No Known Major Psychopathology: A Post Hoc Analysis of SURMOUNT.. Obesity (Silver Spring, Md.), 34(3), 565-578. https://doi.org/10.1002/oby.70122