Premature greying of hair is a complex process, caused due to different reasons in different individuals and needs a thorough history and work up to know the exact cause in your case, but even after that many a times cause can be unknown.
Next Steps
Pl connect to know what all tests need to be taken and the treatment will be based upon that.
Health Tips
Management of stress through meditation, mindfulness, yoga, healthy diet, proper sleep might help with reducing the progress.