People become very engaged with the lives of celebrities because of all kinds of reasons. One idea that is popular is that we need to pay attention to the powerful people in society because they can have a lot of influence on our lives. While that’s not actually really true when it comes to most celebrities, the argument goes that the human brain evolved to deal with much smaller groups of people – just some hundreds – where everyone you knew were people you met, and the powerful people had power directly over you. So you needed to know what the score was with the boss man or woman in your tribe. Celebrities are argued to fill that role for some. But if you go as far as actually believing you have a relationship with someone you don’t, that’s going an extra step into a full on delusion – there is something seriously wrong with your brain, which could be caused by anything from a neuro-chemistry imbalance to a brain tumour to a terrible experience. You need the combination of celebrity obsession and that delusional state for this to happen.