Some people (like myself) suffer from functional dyspepsia, in which GERD-like symptoms are observed with no apparent cause. There's really no standard treatment: some people find relief from PPI's, H2 blockers, small doses of SSRI antidepressants, or changes in diet. Every doctor I've talked to (including one of the top gastric neurologists in the country) agrees that, given a choice between taking PPI's long-term or suffering from functional dyspepsia, they'd take the former every time.
References:
https://www.ncbi.nlm.nih.gov/pubmed/28271513 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4070655/