Effects of Δ9-tetrahydrocannabinol on affiliative social behaviour: A systematic review of rodent studies.

Ahmed M.; Pereira C.; Best L.; Mahmood R.; George T.; Le Foll B.; Boileau I.; Kloiber S. · Journal of psychopharmacology (Oxford, England) · 2026

**Background & Methods** This systematic review examined 49 preclinical studies (146 experiments) investigating THC's effects on affiliative social behavior in rodents, including both wild-type animals and rodent models of social impairment. Studies were identified through MEDLINE and PsycINFO searches, with risk of bias assessed using SYRCLE's tool. **Key Findings** • In wild-type rodents, THC generally reduced affiliative social behavior, with effects most pronounced following acute or adolescent exposure at moderate-to-high doses. • In rodent social impairment models, findings were mixed: low-dose THC sometimes improved social behavior in schizophrenia-related models, while higher doses frequently worsened deficits or produced no effect. • THC's effects on social behavior were substantially influenced by dose, biological sex, developmental timing of exposure, and the specific experimental model used, indicating complex dose-response relationships. **Dosage & Administration** The review included studies examining variable dose ranges and timing protocols. Distinction was made between acute dosing and adolescent developmental exposure. Specific dose parameters and routes of administration were not systematically summarized in the abstract, though the review emphasizes that moderate-to-high doses produced more consistent social behavioral reductions than low doses. **Safety & Adverse Effects** Not reported. The abstract focuses on social behavioral outcomes rather than systemic safety or adverse effects profiles. **Evidence Quality** This systematic review demonstrates moderate limitations in the existing preclinical literature. Risk of bias assessment revealed insufficient reporting in nearly half of included studies, compromising methodological transparency. The authors highlight suboptimal reporting quality as a major obstacle to replicability and generalizability across the literature. Additionally, sex-balanced study design was inadequately represented in prior research. The heterogeneity in outcomes across different experimental models, doses, and developmental periods suggests that current evidence, while extensive in volume, lacks standardization necessary for robust translational validity. The authors conclude that more rigorous preclinical research with stringent methodological standards and transparent reporting frameworks is essential to support clinical translation of ECS-targeted therapeutic strategies for psychiatric disorders.

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