The World Health Organization (WHO) defines mental health not merely as the absence of disorder, but as a state of well-being that enables individuals to cope with life’s stresses, work productively, and contribute to their community. Climate change threatens this capacity in ways that the empirical literature has increasingly documented, although often through small and geographically biased samples. This systematic review aimed to synthesize the evidence on the impact of climate change on mental health. The review was conducted in accordance with the PRISMA 2020 guidelines. The search was con-ducted in September 2024 across five databases – Web of Science (WoS), Scopus, PubMed, SciELO, and Google Scholar – using nine search queries combined with AND/OR operators. Of 436 records identified, 213 met the inclusion criteria. The direction of evidence was classified into four categories. The methodological quality of the 42 eligible secondary studies was assessed using AMSTAR-2. 59.2% of studies reported positive associations. Positive convergence was highest for suicid-al behavior (80%), post-traumatic stress disorder (PTSD) (75.7%), and cognitive outcomes (71.9%). 40.5% of secondary stud-ies reached high or moderate confidence on AMSTAR-2. The association exists but is not uniform. Suicidal behavior, PTSD, and cognitive deterioration show high convergence and identifiable mechanisms; eco-anxiety and well-being show moderate convergence and a conceptual complexity that is not adequately captured. Radical behaviorism provides a functional frame-work for understanding how climate-related mental health deterioration may occur through the extinction or suppression of adaptive behavioral repertoires and chronic negative reinforcement, while also informing potential intervention targets be-yond symptom-focused treatment.