Attitude toward marijuana should take consequences, real or possible, into consideration (copy)

In a past column, I reviewed the acknowledged medical uses of marijuana from the mainstream medical literature. There’s no question that marijuana has medical benefits for specific conditions.

In researching its adverse effects in the same manner, I found the subject very controversial, and many studies have conflicting results. Although it’s recognized that marijuana causes some adverse effects, other untoward effects can be attributed only by association without adequate evidence of causation.

Definite adverse effects:

About 9 percent of those who use marijuana become psychologically addicted; the number increases to 16 percent when use begins as a teenager.

Physical dependence can develop with regular use. The withdrawal is much like that of nicotine with irritability, insomnia, craving and anxiety.

Acute effects may include paranoia and dysphoria in naïve users.

Driving ability is impaired with reduced attention, reaction time and psychomotor control. The accident risk after marijuana use doubles. Driving impairment from alcohol is considered much more dangerous.

Regular marijuana smokers are at higher risk of respiratory symptoms and chronic bronchitis similar to tobacco smokers; the lung effects of modest use do not appear significant.

Cognitive impairment definitely occurs. School performance may suffer. Long-term cognitive impairment is less clear, but evidence suggests difficulties with memory, attention and intellectual function with regular and heavy use particularly when use begins in adolescence. After abstinence from marijuana, the effects are largely reversible but subtle deficits may remain if use is initiated in adolescence.

Adverse effects less clear or unproven as causative:

Regular use can be associated with anxiety and depression. Marijuana is associated with schizophrenia and psychosis but it’s likely that it only exacerbates or reveals existing illness. Many confounding factors may predispose someone to both marijuana use and emotional illness.

Although there is an association with other drug use, there is no evidence marijuana is any more an adolescent gateway to other illicit drugs than alcohol or nicotine. Alternatively, individuals predisposed to drug use may start with these drugs because of easy access. Interestingly, studies demonstrate lower numbers of opioid prescriptions and opioid overdose deaths in medical marijuana states.

Possible adverse effects on brain development are largely theoretical based on non-clinical evidence of changes in brain physiology and neural connectivity that may occur with adolescent use. However, the association of these specific brain changes to higher risk of future addictive behaviors or lower intellectual functioning is unclear.

Marijuana is linked to lower educational attainment and socioeconomic success. However, causality cannot be consistently established since there are so many shared factors that predispose to both drug use and poor life performance.

Although it would be expected that smoked marijuana (much like tobacco) should increase the risk of lung cancer, no consistent evidence exists, at least yet, that it does. The same is true for heart disease.

There is an association with low-birth weight with use in pregnancy. No convincing evidence of increase in fetal loss or birth defects exists.

Attitudes toward marijuana are rapidly changing and its acceptance, for better or worse, is swiftly progressing across America. Nine states and the District of Columbia have legalized marijuana recreationally and 30 states have legalized medical marijuana. Twelve percent of Americans over the age of 12 report use in the past year with considerably higher use in youth.

Marijuana is far from a harmless substance, particularly for youth. The question now is if America, much like with the repeal of Prohibition or its forbearance of tobacco, is willing to accept marijuana as a legal substance and tolerate its adverse effects.

Richard Feldman, M.D., is an Indianapolis family physician and the former Indiana State Health commissioner. Send comments to [email protected].