This systematic review examined available evidence linking exposure to GLP‑1 receptor agonists (GLP‑1 RAs) and dual GIP/GLP‑1 receptor agonists to a range of neuropsychiatric outcomes. These incretin‑based medications are widely prescribed for type 2 diabetes mellitus and obesity and have demonstrated cardiometabolic benefits. Given rapidly expanding population exposure and emergent post‑marketing reports, the authors evaluated whether observed associations with neuropsychiatric events meet criteria for causal inference.
The review applied the Bradford Hill criteria as a structured framework for causal assessment. To inform this evaluation, the authors integrated data from multiple streams: receptor pharmacology studies, preclinical neuroscience investigations, randomized controlled trials (RCTs), observational research, and pharmacovigilance/post‑marketing surveillance reports. The goal was to weigh strength, consistency, biological plausibility, and experimental support for reported associations across neuropsychiatric endpoints.
GLP‑1 RAs and dual GIP/GLP‑1 RAs act on incretin pathways to improve glycemic control and promote weight loss. Several individual agents are mentioned in the review’s keywords and discussion, including liraglutide, semaglutide, dulaglutide, tirzepatide (a dual GIP/GLP‑1 RA), and retatrutide. The review situates these agents’ peripheral metabolic effects alongside evidence that incretin signaling can influence central nervous system (CNS) function, providing a mechanistic basis to examine potential psychopharmacological and neuropsychiatric consequences.
Preclinical neuroscience data and receptor pharmacology were considered to evaluate biological plausibility. These lines of evidence indicate that incretin receptors and downstream signaling pathways can modulate CNS processes relevant to mood, reward, cognition, and sensory function. The review integrates these translational findings as foundational mechanistic support for potential neuropsychiatric effects, while acknowledging limits in extrapolating animal or molecular models directly to clinical outcomes.
The authors reviewed RCTs and observational studies that have reported neuropsychiatric outcomes in patients treated with GLP‑1 and dual GIP/GLP‑1 RAs. Such clinical studies provide experimental and real‑world data but vary in design, outcome ascertainment, duration, and population. Overall, the review indicates that current clinical evidence is mixed and that many studies were not primarily designed to assess neuropsychiatric endpoints, limiting causal inference.
Post‑marketing surveillance and pharmacovigilance reports have raised questions about possible central nervous system adverse events associated with incretin‑based therapies. The review incorporated these safety signals alongside controlled and observational data to assess consistency and temporal relationships. While such reports contribute to signal detection, the authors note that pharmacovigilance data alone are insufficient to confirm causal relationships.
Using the Bradford Hill framework, the review found that some criteria—particularly biological plausibility and limited experimental support—are met to an extent. However, evidence for other criteria, including consistent strength of association and specificity across studies, is generally insufficient. The authors concluded that the overall body of evidence does not yet satisfy the threshold for establishing causality for most neuropsychiatric outcomes.
The review systematically assessed reported associations across several domains:
Depression and anxiety: Investigated across pharmacology, preclinical models, RCTs, and observational reports; biological plausibility exists but evidence is inconsistent.
Suicidality: Considered in safety surveillance and clinical datasets; current evidence does not establish causal links.
Reward‑related behaviour: Preclinical and mechanistic data suggest possible modulation, but clinical confirmation is lacking.
Cognitive effects: Some translational rationale and limited clinical data exist; conclusive evidence of harm or benefit is absent.
Retinal/ocular disturbances: Reported in some post‑marketing contexts; evidence remains insufficient to determine causality.
Across these domains the review emphasizes that plausibility and signals are present but that definitive causal attribution is not supported by current data.
Given the established cardiometabolic benefits of GLP‑1 and dual GIP/GLP‑1 RAs and rapidly increasing therapeutic use, the authors underscore the need for careful clinical risk–benefit assessment with attention to potential neuropsychiatric outcomes. They recommend that clinicians remain vigilant for emergent CNS adverse events and consider individual patient risk factors when prescribing these agents. However, the review does not provide prescriptive clinical guidance beyond highlighting the need for further evidence.
The principal recommendation is the need for prospective, mechanism‑informed clinical studies specifically designed to evaluate neuropsychiatric endpoints. Such studies should prospectively capture mood, anxiety, suicidality, reward‑related behaviours, cognition, and ocular outcomes with appropriate duration and population sampling to address current limitations in causality assessment.
The authors declared no competing interests in the conflict‑of‑interest statement.
(Report based exclusively on the abstract and bibliographic information provided in the source. No additional study details, numerical results, or unpublished data were reported in the source abstract.)