Hi and welcome.
Noone knows what could be going after narcotics consumation. Its side effects arent investigated good enough yet but many bad consequences are reported including coma
and death. It is questionable are his symptoms related to this consumation. I suggest to do gastroscopy and lung xray to evaluate his condition. It can be sign of anxiety
but also a sign of some organic pathology suc has GERD, hiatus hernia
or esophageal strictures. WIsh you good health.