Public stigma and prejudice toward people with psychiatric conditions is highly prevalent and damaging. Explanations for the origins of mental illness can influence attitudes toward people with these conditions. To date, studies exploring the effects of explanations for the origins of mental illness have focused on genetic or environmental explanations, and the impact of evidence-based multifactorial explanations for psychiatric illness on public attitudes remains unknown. Participants were recruited through Amazon Mechanical Turk to watch a 4-min video about the "mental illness jar model"-an evidence-based analogy that explains the complex interactions between genes and environment in the development of mental illness. Participants provided demographic information and completed questions regarding knowledge about the causes of mental illness, and the Prejudice towards People with Mental Illness (PPMI) scale both before and after watching the video. A total of 106 eligible participants completed the study. Watching the video had no significant effect on participants' knowledge about the causes of mental illness (p = 0.06), but there was a significant decrease in prejudicial attitudes toward mental illness (p = 0.0003), the effect size was small (-0.15). The use of this brief video (available at cogastudy.org) is a promising tool to decrease prejudicial attitudes toward mental illness that warrants further study.