The vividness of mental imagery has a key role in the development and continuation of intrusive memories, so for those with PTSD, having hyperphantasia is a substantial risk factor. Both schizophrenia and Parkinson's disease also may be aggravated by hyperphantasia, as high levels of vivid imagery predict the severity of visual hallucinations. In fact, it is possible that hyperphantasia is a ‘trait maker’ for schizophrenia, with both disorders being associated with a smaller primary visual cortex. Individuals with schizophrenia have a 25% volume reduction of their primary visual cortex (V1) and its total number of neurons.
