Dear Doctor: Marijuana seems to be increasingly accepted in our country. But I worry about my kids using it. Is it addictive?

Dear Reader: You're right to be worried -- and not only because marijuana can indeed be addictive.

Marijuana has gained greater acceptance in this country, not in small part because its medical use can stimulate appetite, control nausea and control pain. One potential problem with this degree of acceptance is how adolescents view the drug.

In 2015, 70 percent of high school seniors viewed marijuana as not harmful, according to the National Institute on Drug Abuse's (NIDA) Monitoring the Future survey; in 1990, only 20 percent felt this way. Interestingly enough, the 2015 survey also found that 70 percent of 12th-graders disapprove of the regular use of marijuana.

Perhaps the biggest risk with marijuana is how it affects the adolescent brain. The endocannabinoid system, a vast system of receptors within the brain, spinal cord and smaller nerves, affects multiple brain and body functions. This system continues to develop in humans until the age of 21 or so.

If used frequently in adolescence, marijuana can rewire many of these nerve pathways. These changes aren't seen as much in the adult brain and, if they surface, can be easily reversed by stopping use. In adolescents, however, this rewiring of the nervous system may create addiction.

According to the NIDA, only 9 percent of people who try marijuana become addicted. However, this number increases to 16 percent among those who start using marijuana in adolescence. It increases further if marijuana is used daily in adolescence. In fact, 17 percent of admissions to publicly funded substance abuse programs are related to marijuana.

Some of my patients argue that alcohol is a much more addictive substance and can cause withdrawal symptoms that are life threatening. That is true. However, just because one substance has particularly bad effects doesn't mean another one is safe. There are problems with each.

Marijuana not only causes short-term memory loss, it also affects mental abilities for days after its use. That means a person's ability to plan, organize, solve problems and make decisions is impaired, which has significant ramifications for adolescents trying to retain information learned in school or trying to maintain good study habits.

Further, for those predisposed to schizophrenia, marijuana can induce psychosis and, in younger users, can decrease the age of schizophrenia's onset. People with a familial predisposition to schizophrenia should certainly avoid use.

However, marijuana has not been associated with depression or bipolar disorder, and while those with generalized anxiety are more likely to use marijuana, that connection may be linked more to a need to compensate than to causal effect.

I would advise high school students not to use alcohol or marijuana in adolescence, but the reality is that your child, like many others, may be exposed to these and other drugs in high school. As a parent, be sure to watch for signs of abuse or consistent use, and to note any psychological issues that could lead to frequent marijuana use.

With the greater acceptance of marijuana within our society, increased exposure and the likelihood of abuse are rising. Guide your teenager to hobbies, sports, outdoor activities or simply reading a book as a way to cope with the stressors of high school life. And, above all, keep an open line of communication.

(Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)

Dear Doctor: A woman in the mall near our home collapsed and wasn't breathing. A shopper performed CPR until the paramedics showed up. Later, my friends and I realized that none of us could have helped her. Should we get trained in CPR?

Dear Reader: Only a small percentage of the population in the United States knows how to perform CPR, so the woman you and your friends saw was lucky. As you can probably guess, our answer is yes; learning proper CPR technique is a very good idea.

More than 350,000 people per year in the U.S. suffer from sudden cardiac arrest, which is when the heart abruptly stops beating. Although heart arrhythmias and heart disease are the major causes of sudden cardiac arrest, heart function may also stop due to near drowning, smoke inhalation, asthma attack, poisoning or even a severe allergic reaction.

Cardiopulmonary resuscitation, or CPR, really does make a difference. It consists of two separate components -- chest compression and mouth-to-mouth rescue breathing. (According to the latest American Heart Association guidelines, only individuals who are trained in CPR should attempt rescue breathing.)

When someone goes into cardiac arrest and stops breathing, the first few minutes are critical. Studies show that the survival rate of someone in cardiac arrest can double or triple when prompt and high-quality CPR is performed.

So what happens when you perform CPR?

Your body needs oxygen to survive. When your heart suddenly stops beating, the biological chain of events that provides you with oxygen also stops. Without that oxygen, cells begin to die. Brain damage can occur in just 4 or 5 minutes, and death in 8 to 10 minutes.

The purpose of CPR is to keep oxygenated blood flowing to the victim's brain and other vital organs. This is done by chest compressions, in which you're essentially providing an artificial heartbeat. Although by itself CPR will not restart someone's heart, it can help the person survive until medical aid arrives.

When shown on TV or in films, CPR may look easy. However, where and how you place your hands on a victim's chest to perform compressions is very important. So is the rate and depth at which you press on the chest, as well as exactly how and for how long you release.

That's why it's critical to get certified training. Classes, which are offered throughout the nation, are interesting and easy. The American Red Cross offers classes, and the American Heart Association (AHA) has a list of other training centers.

You'll learn proper CPR technique and may also get trained in the use of an automated external defibrillator, or A.E.D.

Although attending in-person class with fellow students and a mannequin to practice on is optimal, a video on the AHA's updated method of hands-only CPR is available online.

A final thought: Between 70 and 80 percent of sudden cardiac arrests occur in or near the home. Why not make CPR certification a family, neighborhood or even community project? Everyone will be just that much safer.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)

Dear Doctor: I have been taking fish oil capsules daily over the last five years. Is there any benefit in doing this?

Dear Reader: The short answer is "maybe." Scientists have shown that societies with higher fish intake have lower rates of heart disease. The belief is that this benefit comes from fish oil. Fish oil contains substances known as long-chain fatty acids (omega-3 fatty acids), specifically DHA, DPA and EPA, with many health benefits. These fatty acids help lower blood triglyceride levels; lower blood pressure (by 1.5 to 4 points); and have an ability to help the heart relax so that blood flows more easily into its chambers. Furthermore, the omega-3 fatty acids in fish oil have also been linked to a slightly slower heart rate and to a decrease in inflammation.

Small studies have shown that fish oil may be linked to a slight reduction in the formation of plaque in the arteries that supply the heart, but evidence of its ability to reduce the rates of heart attack hasn't been as robust or as statistically significant.

One fish oil finding that was indeed statistically significant was from a large study published in the Journal of the American Medical Association in 2006. That study linked fish oil intake of 250 milligrams per day to a 36 percent reduction in rates of sudden cardiac death. That amount -- 250 mg of fish oil -- equals 1 to 2 servings of fish per week.

One other property that fish oil may have is an ability to reduce electrical excitability of the heart. That reduced excitability may decrease the heart's chances of going into an abnormal rhythm, which can lead to death. Furthermore, among people who have had a heart attack, 1 gram of fish oil per day has been linked to a significant decrease in death rates. The benefits of fish oil have been seen as early as four months after a heart attack and even as late as 36 months after a heart attack. Again, this appears to be related to fish oil's potential protective effect against abnormal heart rhythms after a heart attack.

Fish oil hasn't been shown to decrease the chance of a stroke. Nor has it been shown to decrease the risk or incidence of cancer. In fact, some studies have shown a correlation between fish oil and prostate cancer, but other studies have failed to support that connection.

In summary, fish oil does appear to decrease the chance of sudden cardiac death, but you don't need to take capsules to see this benefit. Eating fish twice a week can do that.

Before you turn to eating tuna fish from a can, keep in mind that tuna has much less omega-3 fatty acids than Atlantic salmon, mackerel or herring. If you don't care for fish, taking 1 gram of a fish oil supplement twice a week will likely yield a benefit. If you've had a heart attack, consider taking 1 gram of fish oil a day.

(Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)