Regardless of the THC content, the amount of tar inhaled by marijuana smokers and the level of carbon monoxide absorbed are three to five times greater than among tobacco smokers. This may be due to marijuana users inhaling more deeply and holding the smoke in the lungs.
Research suggests that the use of marijuana and other drugs by other family members plays a strong role in whether children start using drugs. Parents, grandparents, and older brothers and sisters in the home are models for children to follow.
Researchers are examining the possibility that long-term marijuana use may create changes in the brain that make a person more at risk of becoming addicted to other drugs, such as alcohol or cocaine. Although many young people who use marijuana do not go on to use other drugs, further research is needed to determine who will be at greatest risk.
Researchers are not certain whether any effects of maternal marijuana use during pregnancy persist as the child grows up; however, because some parts of the brain continue to develop into adolescence, it is also possible that certain kinds of problems will become more evident as the child matures.