A meta-analysis of fear appeal effectiveness and theories was conducted, including 127 studies (9% unpublished) with 248 independent samples (N=27,372) from diverse populations. The results showed a positive effect of fear appeals on attitudes, intentions, and behaviors, with an average effect size of d=0.29 (random-effects). Moderation analyses based on prominent fear appeal theories showed that the effectiveness of fear appeals increased when messages included efficacy statements, depicted high susceptibility and severity, recommended one-time behaviors, and targeted audiences with a larger percentage of female recipients. The study concluded that fear appeals are effective at positively influencing attitudes, intentions, and behaviors, with very few circumstances where they are not effective, and no identified circumstances where they backfire and lead to undesirable outcomes. The meta-analysis tested predictions from multiple theories, including the linear and curvilinear models, the health belief model, the parallel process model, and the stage model. The results showed that fear appeals with high depicted fear were more effective than those with moderate fear, and that efficacy statements increased effectiveness. The study also found that fear appeals recommending one-time behaviors were more effective than those recommending repeated behaviors, and that detection behaviors were more effective than prevention/promotion behaviors. The study also examined the impact of gender, culture, and the stage of behavior change on fear appeal effectiveness. Overall, the study found that fear appeals were generally effective across various contexts and populations.A meta-analysis of fear appeal effectiveness and theories was conducted, including 127 studies (9% unpublished) with 248 independent samples (N=27,372) from diverse populations. The results showed a positive effect of fear appeals on attitudes, intentions, and behaviors, with an average effect size of d=0.29 (random-effects). Moderation analyses based on prominent fear appeal theories showed that the effectiveness of fear appeals increased when messages included efficacy statements, depicted high susceptibility and severity, recommended one-time behaviors, and targeted audiences with a larger percentage of female recipients. The study concluded that fear appeals are effective at positively influencing attitudes, intentions, and behaviors, with very few circumstances where they are not effective, and no identified circumstances where they backfire and lead to undesirable outcomes. The meta-analysis tested predictions from multiple theories, including the linear and curvilinear models, the health belief model, the parallel process model, and the stage model. The results showed that fear appeals with high depicted fear were more effective than those with moderate fear, and that efficacy statements increased effectiveness. The study also found that fear appeals recommending one-time behaviors were more effective than those recommending repeated behaviors, and that detection behaviors were more effective than prevention/promotion behaviors. The study also examined the impact of gender, culture, and the stage of behavior change on fear appeal effectiveness. Overall, the study found that fear appeals were generally effective across various contexts and populations.