A certain amount of change may be normal during the teen years, but too drastic or long-lasting a switch in personality or behavior may signal real trouble — the kind that needs professional help. Watch for one or more of these warning signs:
extreme weight gain or loss
sleep problems
rapid, drastic changes in personality
sudden change in friends
skipping school continually
falling grades
talk or even jokes about suicide
signs of tobacco, alcohol, or drug use
run-ins with the law