May 25, 2006

Ritalin Causes Cancer?

An eye-opening study from some Texans.

18  kids, newly diagnosed with ADHD, started the study, only 12 finished.  They showed up on day 1, and blood was taken.  The kids were then given Ritalin (methylphenidate) 20-54mg/d, as part of ordinary treatment, for three weeks.  At the end of three weeks, another blood sample was taken.  The bloods were evaluated for cytogenetic abnormalities. 

In every single case, the frequency of chromosomal aberrations, sister chromatid exchanges (SCE), micronuclei, and nucleoplasmic bridges were all dramatically higher than at baseline.  Not a little higher-- massively higher.

Cytogenetic Abnormalities due to ritalin

The authors had, in their introduction, summarized the absence of substantial evidence (or actually even studies) for carcinogenicity or mutagenicity, except one long term (2 year) high dose study in rodents-- it gave them hepatocellular carcinoma.  But there has been nothing done in humans.

There are some problems with the study, beyond the obvious small sample size.

First, there's no control group.  The assumption is that the only new factor over the three months of the study was the taking of Ritalin, so that is the likely culprit.  Of course, it is certainly possible that something else occurred during those three months that could have caused this effect, such as a new illness, new meds, taking up smoking, etc.  In all twelve people.  At the same time.  Sure, it's possible.

Second, the pretreatment group actually had less sister chromatid exhcanges than are expected on average.  In a follow-up letter letter , the authors indicate that the known average frequencies of SCE are actually based on adults, not kids.  Do kids have lower frequencies in general?  Maybe.

The authors in that same letter also observe that despite the perception that there has not yet been on observed link between Ritalin and carcinogenicity, in fact

"the national toxicology program (NTP)—CERHR expert panel report on the reproductive and developmental toxicity of methylphenidate, indicate that only one study addressed the carcinogenic risk of methylphenidate treatment in humans... conducted by screening pharmacy and medical records, indicated that there was no increase in reports of cancer in a small number of patients taking methylphenidate (only 529 patients)."


I looked up the cytogenetic effects of amphetamines.

One study found methamphetamine exposure correlated to frequency of  micronuclei and SCEs in humans (though, in hamsters, this effect was due exclusively to methamphetamine itself, and not its metabolites; and free radical scavengers also reduced this effect).

An old 2 year rodent study found decreases in number of neoplasms when given dl-amphetamine.  Another study found a similar reduction, especially in pheochromocytomas, pituitary adenomas, and breast adenomas.

But again, these are rare studies, and this one here is the first done, prospectively, in humans.

What is astounding to me, apart from the obvious, is that no one knows this article.  It has not been referenced in any subsequent articles.  I can't find one psychiatrist, academic or otherwise, who has even heard this.  They all look at me blankly: "Really?"

Yet, simultaneously, psychiatrists live with complete confidence that Ritalin is safe.  They've never checked the known information before, of course, so what allows them to be so confident I have no idea; and they certainly don't run Medline once a month "just to keep up with all of science"-- but they're sure of what they know.  Not even an empty patronizing nod to "but of course, our knowledge base is expanding..."

The point is not that Ritalin is unsafe.  This study could be a load of crap, for all we know.  But shouldn't psychiatry have at least heard of this study?  What is the mechanism to disseminate this kind of information?  How long does it take for something like this to hit the psychiatric press?  In other words, given psychiatrists' arrogant confidence, how do they believe they would be informed of new developments?  They don't really read psychiatry journals.  They certainly aren't going to read cancer journals. 

9/5/06 Update Further info suggests this may be a fluke.