Causation, as one of the elements of tort law, has always been examined by lawyers. What has been studied in most legal writing is causation as a physical phenomenon. The discussion related to causation usually emphasizes the apparent act of the actor. Establishing causation due to the existence of psychological effects on individuals is among the topics that, through the judicial practice of European countries, have recently attracted the attention of legal doctrine, especially in Germany. Considering that individuals exhibit different reactions to psychological stimuli based on their personal characteristics and various situations, establishing the causation between the influencer factor and the occurrence of harm, as well as determining a standard for it, is difficult. This research, using a descriptive-analytical method and relying on library resources, seeks to answer the following questions: What specific criteria can be identified for establishing causation in the presence of psychological effects? How can causation be established in Iranian law when a psychological influencer factor exists? The findings show that the judicial practice of European countries distinguishes between intentional and unintentional actions of the influencer factor and provides primary and supplementary criteria, all of which smooth the path to establishing adequate causation. In Iranian law, in cases where an intervener unintentionally causes harm due to psychological influence, the responsible party can be determined through general rules governing adequate causation, the rule of fraud**, and the fault of the victim party.