What causes headaches?

In terms of what causes headaches, it's again coming back to primary headaches and secondary headaches. In terms of primary headaches, the cause often is genetic, at least we think in the majority of the so-called primary headaches, where we think what someone has done is inherited a set of genes that has made their pain system prone to being dysfunctional periodically or on a continuous basis. So there's nothing wrong on the outside. There's no structural lesion that one can find. It is all a problem of function within the brain. For the secondary headaches, it is a multitude of reasons. It can be a brain tumour. It can be high pressure in the brain. It can be low pressure in the brain. It can be a multitude of lesions within the brain. It can also be things that are outside of the brain itself that can make you more prone to having these headaches.