As your children become closer to age 18, they begin taking on responsibilities such as part-time jobs, college applications and driving. If you have preteens or young adults, be aware of dangerous behaviors that could affect their future, such as underage drinking.

Parents should know these common signs of teen substance abuse.

Strange behavior or mood

If your child had a few drinks or tried drugs during a night out with friends, he or she may behave unusually upon returning home. Look for clumsiness, falling, uncontrollable laughing, exhaustion, withdrawal, nausea and vomiting, unexplained appetite and other signs that something is off. In the long term, look for mood swings, aggression, anger and depression.

Poor personal hygiene

You may notice that your child smells of smoke, has soot or burn marks on the fingers or lips, or has generally poor hygiene and an unkempt appearance. Red eyes and alcohol on the breath also signify substance abuse.

Change in friends

If your teen hangs out with a new crowd that you have not yet met, he or she could be keeping these friends away from you for a reason. This is especially true if your child also withdraws from family events, other friends and previously loved activities and hobbies. He or she may be secretive and less willing than usual to share details about school and social life.

Unexplained absences

Does your teen unexpectedly disappear or fail to show up at home or school? Has the school contacted you about your child missing class? If home life and academic performance take a nosedive and your teen does not seem engaged or present, substance use could be a factor in this shift.

Although many parents attribute these signs to the moodiness and stress of teenaged years, you should talk to your child about substance use. Medical and/or psychological treatment helps many individuals with a history of drug or alcohol addiction move forward with a healthy lifestyle.