Collective delusions are false beliefs that have been spread within societies and amplified in social groups. Collective delusions can have catastrophic social consequences. An example of a harmful collective delusion within society is the belief that climate change is a hoax perpetrated by scientists seeking personal advantage, this can decrease people's intentions to minimize their carbon footprint. Another example is the false belief that pharmaceutical companies hide data about harmful side effects of vaccines which in turn reduces people's intentions to get vaccinated.