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Freakonomic Mental Health

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.

A Tale of Two Studies: abortion and mental health

17 Dec, 08 | by Steven Reid, Evidence-Based Mental Health

I came across both of these statements in the medical press last week:

  1. Abortion does not cause mental health problems, says large review
  2. Abortion is bad for your mental health

Which one to believe? The first was a news headline in the BMJ, referring to a recently-published systematic review published in Contraception, a journal dealing with matters related to…contraception. The second is the editorial summing-up of a cohort study in the current issue of the British Journal of Psychiatry. In the hotly-contested battle over abortion and choice these contradictory findings will be welcomed as further ammunition by both sides.

Have a look at the two papers though, and it’s not so clear that their findings really are in such stark opposition. The systematic review summarises 21 studies looking at elective abortion and long-term mental health outcomes. As is usually the case with observational research poor quality studies found the biggest differences. The highest quality studies (using better methods) found few, if any, differences in psychological outcomes between women who had abortions and the comparison groups. The second study is an analysis of data from a birth cohort in New Zealand – it arrived too late for inclusion in the systematic review but would clearly be considered good quality. Here some differences were found: abortion was associated with a small increase in risk. Women who had an abortion were 30% more like to have subsequent mental health problems (depression, anxiety, or drug misuse) when compared to other pregnancy outcomes.

You can try and explain this positive finding by looking at the differences in methods and comparison groups, as well as differing abortion legislation in the UK, US and New Zealand, but it’s difficult to argue with the authors’ comment that “for a minority of women abortion is a highly stressful life event which evokes distress, guilt and other negative feelings that may last for years.” That seems pretty obvious to me and raises the question of whether in this instance more research really is needed.

So do these studies inform the debate on abortion? I’m not convinced that they will add much to what are primarily moral arguments but one consistent finding is the lack of evidence that abortions reduce the risk of mental health problems for women with an unwanted pregnancy. Despite this, over 90% of abortions in the UK are undertaken on the grounds that to proceed with the pregnancy would pose a serious threat to the mental health of the woman. Isn’t it time that the law acknowledged reality: that access to abortions in the UK is largely unrestricted?

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