By Jonathan Purtle

Earlier this month, Pennsylvania State Sen. Daylin Leach (D., Montgomery-Delaware) announced plans to introduce a bill that would legalize marijuana —  not just for medical purposes, as New Jersey recently did, but also for recreational use.  The substance would be regulated by the state in a way similar to alcohol and tobacco.  As Leach describes on his website, the bill is founded on the idea that marijuana is no more harmful, and less addictive (this is debatable), than both these substances and that the financial costs of keeping marijuana illegal are enormous. Citing data from the White House Office of National Drug Control Policy, Leach points out that 24,685 marijuana arrests were made in Pennsylvania in 2006 — translating into $325 million in criminal justice costs.

Leach's proposal follows referendums in Colorado and Washington that recently gave those states the green light for recreational marijuana use.  And while  the Pennsylvania bill will likely go up in smoke — Gov.  Corbett has vowed to veto the bill if it reaches his desk — it seems high time to explore the potential pros and cons of legalizing marijuana from a public health perspective.

First the cons.

Let's assume that marijuana is 100 percent bad for the mind and body and that legalization would lead to increased consumption. While the notion that marijuana is all harm and no good is debatable — advocates of medical marijuana tout its therapeutic benefits — evidence of its adverse health impacts is strong. A White House document entitled "The Public Health Consequences of Marijuana Legalization" synthesizes some of this research. Outcomes include respiratory problems (smoke is never good for lungs) and cognitive impairment.

The science says that the less marijuana a population consumes the better.  But would legalization actually result in more people toking up more often? The answer is hazy. Economists at RAND, the non-partisan think tank, crunched the numbers and concluded that marijuana consumption would probably increase with legalization, but they had little idea how large the increase would be.

Now the pros.

The most clear-cut public health benefits of marijuana legalization would likely result from reductions in incarceration. While there are many ways in which incarceration negatively impacts public health — by disrupting monogamous sexual partnerships, for example, which increases the number of sexual partners that  people have, and thus the spread of sexual transmitted diseases — let's just focus on the financial costs of putting people behind bars for weed. As Senator Leach notes, Pennsylvania taxpayers spend around $325 million annually on marijuana-related arrests. While not all of this goes to incarceration, legalization would free up a lot of public money that could be invested in health.

As described in a previous post, research has documented a link between increases in public health spending and improvements in population health.  A large, multisite study found that a 10 percent increase in local public health department spending was associated with a 6.9 percent decrease in infant mortality, a 3.2 percent decrease in deaths from cardiovascular disease, a 1.4 percent decrease in deaths from diabetes, and a 1.1 decrease in deaths from cancer.  The Philadelphia Department of Public Health's budget would double if the state took $200 million of marijuana-related criminal justice savings and invested it in the city's health. This would translate into a substantial number of lives saved. Exactly how many? We can only speculate.

Data from the 2010-2011 National Survey on Drug Use and Health indicate that an estimated 10.82 percent of Pennsylvanians over the age of 12 used marijuana in the past month — as did nearly one-third (31.16 percent) of residents between the ages of 18-25. The estimates are similar for New Jersey — 10.73 percent and 31.79 percent, respectively. While uncertainty abounds regarding the public health costs and benefits of legalizing marijuana, one thing is for sure — people are using it, legal or not.

Read more about The Public's Health.