Stress doubles the risk of a person's hair turning grey before they turn 30.
A study has found that anxiety and depression have a more significant impact on follicles compared to other factors such as diet and exercise.
The stress hormone cortisol and mental health medications can cause harmful scalp inflammation that removes the colour from someone's locks.
Data suggests that half of humans go grey by the time they have turned 50 but millions start the transition years and even decades beforehand.
A team at King Saud University in Saudi Arabia compared rates of greying among more than 1,000 people aged between 18 and 29.
Half found at least one grey hair during their 20s and the results show that anxiety increased the chance of greys by 2.24 times and depression by 2.56.
Turki Albinhar, author of the study, said: "Lifestyle changes such as quitting smoking, a balanced diet, and managing stress can help mitigate risk."