Final answer:
PMS symptoms can occur before a woman's menstrual period and can vary in severity. The symptoms are commonly experienced during the late teens and early twenties when hormone levels are fluctuating.
Step-by-step explanation:
PMS stands for premenstrual syndrome, which refers to a group of physical and emotional symptoms experienced by some women before their menstrual period. The severity of PMS symptoms can vary from person to person and can also change over time. While there isn't a specific age at which PMS symptoms are worse, they commonly occur during the late teens and early twenties, when a woman's menstrual cycle is often irregular and hormone levels are fluctuating.