Adolescent Cannabis Use: Changing Minds (For the Better? Or For the Worse?)
In light of widespread legislative efforts to legalize medicinal and recreational use of cannabis, we reviewed the scientific evidence pertinent to this issue, and published a review and synthesis of the findings in an article that appeared in the March/April 2012 issue of Missouri Medicine. The studies clearly demonstrated significant adverse effects of cannabis smoking on physical and mental health and on social and occupational functioning.
Evidence that cannabis use harms health continues to accumulate. In a prospective, longitudinal study of over 1000 individuals studied systematically over four decades, Meier et al (2012) found that persistent cannabis use in adolescence is associated with decline in cognitive function in midlife, evident as loss of eight (8) IQ points on average and as deficits in memory, attention, and mental processing. The findings were substantiated by interviews with collateral sources, a person who knew the subject well and judged the changes as conspicuous (i.e., “visible to the naked eye”). A second recent study (Zalesky A et al. 2012) utilized neuroimaging techniques and identified structural alterations affecting brain pathways in persistent cannabis users. This and other well documented structural impairments in both white and gray matter of the brain are likely pathological substrates underlying declines in cognitive function and increases in neurological and psychiatric disorders associated with cannabis use. The study authors’ conclusion that “long-term cannabis use is hazardous to the white matter of the developing brain” should serve as clear warning.
There is a perplexing disconnect of the general public and law-makers from scientific evidence of significant long-term harms related to persistent cannabis use, particularly in younger users. Activists in Missouri failed to obtain the signatures necessary to place a marijuana decriminalization initiative on the 2012 ballot. However, medical use of marijuana has been approved in 17 states, and Denver, Colorado currently has more medical marijuana dispensaries (204) than Starbucks and McDonald’s combined {http://www.cbsnews.com/2102-18560_162-57536827.html?tag=contentmain;contentbody}. Given that scientific evidence of damage and deficit from cannabis use has not been restricted to health professionals but has been disseminated in popular magazines and TV (including a recent 60 minutes segment), one must assume that other motives (economic, political, personal) besides public health are involved in the relentless pressure to legalize or decriminalize cannabis use. Ironically, lobbyists for the medical marijuana industry are among the most vocal opponents of cannabis decriminalization.
Results from recent national public health surveys indicate that marijuana use among teens continues to rise, while tobacco, cigarette and alcohol use are at historic lows among this group (O’Malley PM et al. 2012). More disturbingly, these surveys show a decline among teens in the perceived risk of harm from marijuana use. Clearly, there is a high price to be paid for ignoring scientific evidence against widespread use of cannabis. The most vulnerable population, our youth, will inevitably be hurt in terms of academic achievement, increased risk of mental illness, fatal traffic accidents, and other concerns summarized in our Mo Med paper. The challenge is to translate these findings to effective public health efforts in order to reduce exposure to harm and the costs to individuals and society that result.
Sincerely,
References:
Svrakic DM et al. Legalization, Decriminalization & Medicinal Use of Cannabis. Missouri Medicine 2012 109(2): 90-98)
Meier MH et al. Persistent Cannabis Users Show Neuropsychological Decline from Childhood to Midlife. Proc Natl Acad Sci doi: 10.1073/pnas.1206820109) .
Zalesky A et al. Effect of Long-term Cannabis on Axonal Fibre Connectivity. Brain 2012 135(7):2245-2255)
O’Malley PM et al. 2012 Monitoring the Future national results on adolescent drug use. Ann Arbor, MI: Institute for Social Research, University of Michigan).