You have a 16-year-old patient who has been doing poorly in school. He has withdrawn from his social group and quit the sports in which he excelled. He admits to using marijuana “maybe once or twice a week.” But you and his parents suspect that it is much more often and contributing to the change in his behavior and school performance.
They would prefer he not use marijuana at all but could maybe be comfortable with some arrangement in which their son could demonstrate that his usage was indeed limited to once or twice on the weekends. They ask for your help with crafting a contract that might include “some urine or blood test” that would allow them to be sure their son was adhering to the contract.
Dr. William G. Wilkoff
You explain to them that there are hazards associated with setting up contracts such as the one they are proposing. One revolving around the issue of trust. Another being that he may be addicted to the point that a compromise that includes scaling back his usage is unlikely to succeed. And, finally, you tell them that because of marijuana’s pharmacokinetics, their son’s urine tests will always be positive and not reflective of the how much he is using or whether he is intoxicated.
Scenarios similar to this are increasingly common for those of us living in states that have legalized recreational cannabis use. The absence of a laboratory test that can determine when a person is impaired by marijuana has made life difficult for law enforcement officers accustomed to relying on breath and blood tests for alcohol to confirm their suspicion that a driver is under the influence.
In addition, because marijuana is still detectable days after it is used, many well-paying jobs go unfilled when potential applicants are hesitant to submit to a required drug test. The quirky pharmacokinetics of cannabis are well-known to the recreational users and they see no reason to risk failing a urine test regardless of how good the job may be.
This lack of a reliable indicator of cannabis intoxication has not gone unnoticed, and in a recent study published in the journal Neuropharmacology, researchers at Massachusetts General Hospital in Boston report some hopeful results using fNIRS brain scanning. The investigators observed an increase in the level of oxygenated hemoglobin concentration (HbO), which is a type of neural activity signature, in the prefrontal cortex region of the volunteers who reported being impaired.
While a brain scan may sound like an unwieldy tool to use on roadside sobriety stops, the researchers report that portable scanners – some using skull cap sensors – could be easily adapted for use by law enforcement in the field. This technology also could be used by employers on the job site to test truck drivers and heavy machine operators at the beginning of each shift, thereby allaying the fears of responsible cannabis users.
This technology might be helpful to you in advising the parents of the 16-year-old you suspect of heavy usage. It would certainly help in confirming the suspicion that he is using more often than he claims. However, the contract the parents propose still may not work. If this young man demonstrates on multiple attempts that his word can’t be trusted, technology isn’t going to be the answer.
Dr. Wilkoff practiced primary care pediatrics in Brunswick, Maine, for nearly 40 years. He has authored several books on behavioral pediatrics, including “How to Say No to Your Toddler.” Other than a Littman stethoscope he accepted as a first-year medical student in 1966, Dr. Wilkoff reports having nothing to disclose. Email him at pdnews@mdedge.com.