The teen years are a time of enormous change, and a certain amount of emotional upheaval is to be expected. But how do you know what’s normal and what’s not?

Experts say to watch out for these red flags:

• Sleeping far too much or too little
• Loss of interest in favorite pastimes
• Unexpected or dramatic decline in academic performance
• Weight loss and lack of appetite
• Personality changes, such as unusual aggressiveness and anger

These changes could signal depression, substance abuse, an eating disorder or other mental illness. The good news is mental illness can be treated. Your doctor or a counselor at your child’s school can help you decide what steps to take next.