Background and aims: Social media increasingly shapes body image by promoting often unattainable beauty ideals. Concurrently, targeted online marketing of image- and performance-enhancing drugs (IPEDs) exploits these vulnerabilities, intensifying anxiety and fostering maladaptive behaviours such as problematic usage of the internet (PUI), compulsive exercise, and IPEDs consumption. This study explores these behaviours across nine countries and examines how PUI, excessive exercise, and IPEDs use predict appearance anxiety, aiming to inform targeted prevention strategies for at-risk populations. Methods: A total of 3,514 participants from nine countries completed a web-based survey assessing sociodemographic data, appearance anxiety (AAI), problematic internet use (PIUQ-9), excessive exercise (EAI-R), and IPEDs intake. Results: Appearance-related anxiety was observed in 12% of the participants, with the highest prevalence in Mexico (20.7%), Japan (13.8%) and Italy (13.6%). Median PUI scores were highest in Mexico (22.57) and Singapore (21.59). Excessive exercise was reported by 3.6% with no significant country differences. IPEDs use was reported by 28.3% of the sample, with the highest rates in Japan (60.6%). Logistic regression analyses revealed that PUI, excessive exercise and IPEDs use were significant predictors of appearance-related anxiety. Discussion and conclusions: The strong associations between PUI, excessive exercise, IPEDs use, and appearance anxiety underscore the complex interplay between online exposure, body image concerns and mental health. Cross-country differences suggest that socio-cultural factors influence appearance-related anxiety. These findings highlight the need for culturally sensitive interventions and policy measures that address the impact of digital media on body image, particularly to protect vulnerable populations.