A recent study carried out in Finland and Germany - Use of Antiepileptic Drugs and Dementia Risk—an Analysis of Finnish Health Register and German Health Insurance Data - concluded that although some antiepileptic drugs did correlate with an increased risk of dementia, gabapentin did not.
I'm been taking gabapentin for neuropathic pain for nearly 10 years. Currently I'm on 2,400 mg daily (800 mg 3 x a day) - the recommended maximum dosage is 1,800 mg daily, with an absolute maximum of 3,600 mg. For me it takes the edge off the pain, although not always as much as I would like. *
* Consider that an example of British understatement.