Should the U.S. Legalize Marijuana?

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The 2002 edition of the respected British Medical Journal, reading “Marijuana and psychiatric illness: the link grows stronger” was a turning point in the medical literature regarding the connection between marijuana use and mental illness. In that issue, Zammit and colleagues looked at 50,087 Swedish conscripts, to conclude that marijuana use in adolescence is a risk factor for schizophrenia, independent of the effects of other drugs or social personality traits (Zammit et al 2002).

An established link between marijuana and psychosis and schizophrenia has emerged in other respected research journals (Ashton 2001; Hall and Solowij 1998; Jha 2002; Johns 2001; Patton 2002). In a New Zealand study, Arseneault and colleagues discovered that using marijuana as an adolescent increases your risk for schizophrenia even after adjustment for pre-existing childhood psychoses (Arseneault et al 2002). Meta-analyses have found that eliminating marijuana use could reduce incidence of schizophrenia by 8% among a nation’s population (Arseneault et al 2004). In the U.S. that means that stopping marijuana use could reduce schizophrenia by more than 19,000 people.

Additionally, heavy marijuana use also can lead to psychosis. Murray concluded that those who smoked marijuana at age 18 and 15 were 60% and 450% more likely to achieve psychosis, respectively (Jha 2004). Psychosis has even been linked with oral – not smoked – marijuana administration, leading Favrat and colleagues to conclude that “while the oral route of administration achieves only limited blood concentrations, significant psychotic reactions may occur” (Favrat et al 2005). Marijuana use is also linked with depression (Patton et al 2002). These dire statistics about the link between mental illness and marijuana use have officials worldwide worried. Based on these recent assessments, Australian public health officials, once neutral on marijuana’s role in mental illness, called their high levels of use a “ticking time bomb.”