Final answer:
Stress can make individuals more susceptible to catching colds.
Step-by-step explanation:
Research has found that those who are suffering from stress are more susceptible to catching colds. This is because high levels of stress can weaken the immune system, making it harder for the body to fight off infections and illnesses.
For example, a study published in the Proceedings of the National Academy of Sciences found that stressed individuals had a higher chance of developing cold symptoms when exposed to the common cold virus.
Therefore, option d, 'more susceptible to catching colds,' is the correct answer.
Learn more about Effects of stress on immune system