Furious Seasons

June 25, 2008

ADHD Gene Fails To Predict Response To Ritalin, Adderall

This will have to count as a setback for neuropsych researchers, who've been insisting for years that if they can find a central gene (or genes) tied up with a particular mental disorder, then they could predict response to drugs used to treat the disorder. New research is out today in Neuropsychopharmacology asserting that discovery of a gene polymorphism that seemed to predict the severity of ADHD symptoms has not lead to an ability to predict patient responses to Ritalin, Adderall and the other ADHD-treatin' stimulants. And that runs counter to what researchers had expected.

"'What we found is that the children who have two copies of the Val isoform had an even harder time orienting their goals than children who are homozygous for Met [that is, have two copies of the Met isoform] or even Val/Met,' [the researcher] said. Each person two copies of the COMT gene, one from each parent.
"Yet the researchers observed no correlation between the type of variant and response to methylphenidates; the drug reduced ADHD behavior in all individuals regardless of genotype.

"'We expected this polymorphism would also modulate response to medication, but it didn't,' said Joober. 'In other words, that means that whether you have the Val or Met allele, it will not change your level of response to medication with respect to task- or goal-oriented behavior.'"

Some researchers note that this is actually an opening door for more complex research into the neurology of ADHD and drug response.

I'll believe it when I see it.

Posted by Philip Dawdy at June 25, 2008 10:46 AM

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Comments

Philip, do you really believe there's no genetic component to mental illness? Simply because COMT isn't involved in ADD doesn't mean that no genes are. In fact, twin studies have shown that most mental illnesses show a highly significant genetic component, although the genes involved may be particularly hard to pin down.

Ritalin/Adderall primarily affect synaptic dopamine levels. Thus, the researchers here thought that COMT genotype, which also affects synaptic dopamine levels, might be involved in ADD, and this is exactly what they find. However, while they expected some interaction between COMT and drug response, they found that COMT did not affect the degree of improvement that Ritalin produced.

This is a two-part study. The first part, the demonstration of a link between COMT and ADD, is definitely a positive one. It shows that COMT is "tied up" in ADHD. The second part is disappointing because it suggests that one of the main practical applications of this research, the tailoring of treatment plans to individuals' genotypes, may not work out in this particular case.

However, this study adds to a growing body of evidence linking COMT to mental illness. Caspi et al., 2005, showed a significant link between the same val158met polymorphism discussed here and the probability of developing schizophrenia after adolescent cannabis use.

Posted by: Simon at June 25, 2008 05:11 PM

simon, can you show me where i said there wasn't in this post? or are you just trying to bait me?

Posted by: Philip Dawdy at June 25, 2008 06:19 PM

Sorry, I misread your post. What I said above may not be particularly relevant.

Posted by: Simon at June 25, 2008 09:16 PM

It is likely that ritalin, like antidepressants, can cause damage to mitochondria.

Posted by: Lilly NC at June 30, 2008 01:04 PM