SCARBOROUGH — A recent story in the Portland Press Herald (“Legal pot foes fight perception problem,” Dec. 23) highlights the disturbing trend of young people to regard marijuana as harmless.

In the article, an important note of caution is raised by Scott Gagnon, director of the Maine chapter of SAM (Sensible Approach to Marijuana) about “the need to get more science-based information out there.”

He cites literature about the increased potency of marijuana available on the street today, and a variety of significant potential health risks by now familiar to clinicians and researchers but not widely recognized by the public.

Brain imaging studies show that the frequent early use of marijuana may affect the as-yet-not-fully-mature frontal lobes of teenagers’ brains. These regions are crucial for planning, judgment, risk assessment and other “executive functions” that make us fully human. In effect, they function as the brain’s CEO, or “conductor of the orchestra,” coordinating input from other parts of the brain.

Damage to these developing regions may ultimately impact many capabilities, including overall intelligence. A recent study from New Zealand demonstrates an average loss of several IQ points related to chronic early marijuana use. Ultimately, this may result in diminished educational success and vocational achievement with significant loss of earning capacity over a lifetime.

Another serious consequence of chronic marijuana use by young people is its role as an “accelerant” for the emergence of serious mental illnesses such as schizophrenia or bipolar disorder. This has been the disturbing clinical observation of “early intervention” programs both around the world and here in Portland (the Portland Identification and Early Referral Program) that attempt to identify and treat young people at high risk of developing a first psychotic episode.

Even when successful treatment has arrested or diminished the frightening auditory hallucinations or paranoid delusional fears precipitated by heavy use of marijuana, later use can cause these symptoms to reappear with a vengeance. Unsettling but hardly surprising, since pure tetrahydrocannabinol (the component responsible for marijuana’s “high” and other familiar effects) can cause similar psychotic symptoms to occur transiently even in normal research subjects.

The even more widespread use of the drug by young people that is certain to occur as efforts at legalization of marijuana move forward thus amounts to an ominous uncontrolled experiment in “public health in reverse.”

For some undetermined number of vulnerable young people among the many who are heavy marijuana users, the drug may prove to be anything but a harmless recreational experience. It may, instead, bring out into the open a latent psychiatric disorder that could profoundly affect that individual’s life.

Even before parents and peers, high school guidance counselors may be the first to recognize that deterioration in a student’s speaking or writing, odd uncharacteristic behavior, social isolation or any of a number of other changes should compel a professional evaluation. At other times, the onset of schizophrenia or another psychotic-level illness may not be obvious until a subtle progressive deterioration in functioning leads to a first psychiatric hospitalization.

Distinguishing between what changes in a young person’s thinking and behavior are temporary minor disturbances of adolescence, and which have more worrisome significance, isn’t always easy. Sometimes a clear-cut history of major mental illness in other family members may warn that suggestive symptoms in a young person need immediate careful assessment.

Strict avoidance of any further use of marijuana or another brain-altering substance may, for luckier individuals, cause symptoms to disappear. But often so-called “prodromal” symptoms intensify over time into diagnosable psychiatric illness.

Risks of marijuana addiction – as defined by an individual’s persistent uncontrollable seeking and use of the substance despite repeated harmful effects on his or her health, legal status and behavior – are recognized by professionals treating a growing number of such cases.

Respiratory damage from inhaled marijuana smoke is at least as damaging to small airways, drag for drag, as tobacco smoke, according to an expert in lung disease presenting a recent Grand Rounds at Maine Medical Center.

Regardless of what position one takes in this complex debate, informed opinion based on peer-reviewed scientific literature should be a part of the public discourse.

— Special to the Press Herald