To you and your GP, reducing stress is a good goal, whether it specifically causes grey hair or not. Unless you're writing code to stop an imminent killer asteroid, most jobs and tasks are not important enough or urgent enough to make you feel bad. If you feel stressed, long term, de-stress your job or change it.
There is some evidence for chronic stress causing premature achromotrichia,[24] but no definite link has been established. It is known that the stress hormone cortisol accumulates in human hair over time, but whether this has any effect on hair color has not yet been resolved.