However these same changes can occur with anxiety, depression other mental health disorders or stress. It is important to observe your teenager closely for other changes. If they are eating less, avoiding normal activities or gatherings with friends, having trouble sleeping or seem sadder than normal then you should be concerned.
Teenagers have stressors that many parents dont quite understand especially on social media. If the behaviors are disruptive to your family dynamic or seem to last longer than you expect, then speak with your child's physician.