If the mental/emotional symptoms seem severe or long-lasting or reoccur often, then it might be time to seek help.
Mental illness is complicated. Brains are complicated. Teens are complicated. The three together are a challenge.
Depression and anxiety are two sides of the same coin and often appear together.
A common first sign of an issue is a sudden and then ongoing drop in grades and/or a drop in interest in favorite activities.
Insomnia (not falling asleep or waking up often) can also be a concern.
Excessive worrying about little (or big) things that doesn't go away is also a concern.