In many cases, asthma and GERD may coexist in the same patient. Some experts may disagree on whether asthma causes GERD or results from GERD; however , we do know that at least half of all patients with asthma suffer from GERD. One possible cause could be the medication that asthmatics take, which can slow down the muscles of the esophagus and stomach. Another possible cause could be the extreme coughing and wheezing that asthmatics frequently suffer, which place a burden on the upper gastrointestinal system.

It is also possible that GERD causes asthma. This may happen in one of two ways. First, the aspiration of small amounts of acid into the lung causes spasm of the air passages. Second, acid causes bronchospasm by stimulating esophago-bronchial reflexes.