Here is a paper that looks at whether there is a statistical connection between schizophrenia (specifically) and head injury. This is an extract from its conclusions:

“Overall, there was no association between either concussion or serious head injury, and schizophrenia (cases and controls were equally likely to have had an admission for these reasons)...The parsimonious interpretation of the reported findings is that there is no association between either concussion or head injury and the later onset of schizophrenia.”