1 Oct, 09 | by Steven Reid, Evidence-Based Mental Health
More antidepressants please…and bump up the Ritalin too. That seems to be the suggestion from this study published by the National Bureau of Economic Research in the US, making a link between new drug treatments for depression and ADHD and falling crime rates (Hat tip: The Economist).
Since the 1990s violent crime rates have declined markedly (no, it’s true, really), especially in the US. Criminologists have struggled to explain the trends as the usual suspects seem to have had little impact. So enter the economists with their alternative explanations, such as Steven Levitt (he of Freakonomics fame) presenting evidence that legalizing abortion in the 1970s led to a decline in the number of young people at risk of criminality, thus reducing crime rates.
In their provocative paper, A Cure for Crime?, Dave Marcotte and Sara Markowitz use data on international drug sales and crime rates as well as more detailed US data from the National Comorbidity Study (showing that in those with a mental disorder the percentage receiving treatment has increased from 20 to 33%) and national prescribing rates to show that ‘the countries with the largest declines in crime rates in the 1990s were almost exclusively those with the fastest growth in SSRI sales’. Details of the analysis are in an ungated preliminary version of the paper here. To control for overall improvements in health care they also looked at the impact of the non-psychotropic medicines, statins and COX-2 inhibitors which have also seen a rapid growth in prescriptions, but here there was no effect. They found that that increased prescribing of psychiatric drugs, notably SSRIs and stimulants (Ritalin), were associated with a reduction in violent crime and go on to conclude:
“Our evidence suggests that, in particular, sales of new generation antidepressants and stimulants used to treat ADHD are associated with rates of violent crime, with weaker evidence that anti-psychotic medications played a role in declining crime rates. The magnitude of the elasticities estimated here are clearly small. We estimate that a one percent increase in the total prescription rate is associated with a 0.051 percent decrease in violent crimes. To put this in perspective, doubling the prescription rate would reduce violent crimes by 5 percent, or by about 27 crimes per 100,000, at the average rate of 518 crimes per 100,000 population. While doubling the prescription rate seems like a large change, it has been estimated that 28 percent of the U.S. adult population in any year has a diagnosable mental or addictive disorder, yet only 8 percent seeks treatment (USDHHS 1999). Doubling the treatment rate would still leave a substantial portion of the ill untreated.
From the beginning to end of our panel, prescriptions per visit increased by 41 percent. Our elasticity estimates imply that this would reduce the total number of violent crimes committed by about 35,000. In fact, the total number of violent crimes reported to police declined by 300,000 during the period. Our estimates imply that just under 12 percent was due to expanded mental health treatment.”
Medical journals tend be dismissive of natural experiments and ecological studies such as this, considering them pretty weak evidence. But given that questions like this are never going to be answered by randomized controlled trials, if the methods are robust some freakonomic epidemiology may be just what we need.