What causes teenagers to make choices that could destroy their future, and

why do they give in to peer pressure?

Dr. Phil gives a wake-up call to 16-year-old Chris and 19-year-old Brett, two young men whose days are spent smoking dope, drinking and engaging in petty criminal acts. Could your child be headed down a dangerous path? Heed the following warning signs.

#1 Teen warning sign: Isolates from the family.
If your once social child starts spending an inordinate amount of time away from home or locked in his or her room, Dr. Phil says this is a red flag. If your teen starts withdrawing from you or your spouse, there's a reason. As a parent, it's your responsibility to identify what's behind the change.

#2 Teen warning sign: An extreme shift in mood.
Is your child garrulous and friendly one moment, then taciturn and angry the next? Don't just chalk it up to growing pains. Dr. Phil says he or she may be hanging out with the wrong crowd, or experiencing changes " hormonally, neurologically or socially.

"One thing to do is not to let it just go," Dr. Phil warns, "because they get bigger, they get stronger, they get more rebellious. It's never too late."

In the case of Chris and Brett, both teens started experimenting with drugs and/or alcohol, unbeknownst to their folks. Chris' parents found a baggie of marijuana in his room, and Brett crashed three cars, resulting in two DUIs. If you suspect your child is using drugs, click here for signs to look for.

#4 Teen warning sign: Family history of alcoholism and drug abuse.
Brett's mother, Janene, admits that she was hooked on methamphetamine for 12 or 13 years. Now five years sober, the mom believes her dalliance with drugs is fueling her son's alcohol abuse.

"There clearly is a higher incidence with teens, if they've had this history in their family," Dr. Phil says. "Maybe it's genetic; maybe it's not. Maybe it's just that the modeling is there."

Click here for a list of alcohol addiction resources.

#5 Teen warning sign: Taking risks.
Don't chalk your child's truancy, vandalism or petty theft up to "teens being teens."

"When your teen just seems to throw caution to the wind, not care about consequences " all around bad sign," Dr. Phil warns. "It indicates a number of things, one of which is that they don't have the ability to connect their choices with their consequences."

Other warning signs to look out for are: declining grades, using street or drug language, a diminished interest in hobbies and a lack of appreciation for family values.

"You can't be in denial about what's going on. Don't kid yourself that these bad things just happen to other people's kids. Know what's going on with your child. Make sure they understand the consequences of their actions," Dr. Phil says. "Make sure they're living consistent with the values you hold so important."

Top Five Warning Signs that Your Child is in Trouble

From the Show