Definition*: Cognogen—Cog-no-gen: A belief that contributes to psychological or physical pathology*The term cognogen is a neologism. We are all familiar with the idea of diseases being caused by bacteria and viruses. We know that infectious disease can be transmitted person to person and across the population. However, misguided beliefs can be as dangerous and transmissible as a bacteria and virus! Dr Johanna Murphy presented a fascinating Morbidity and Mortality round at Queen’s University on this topic last week.