Comment by hirvi74
3 days ago
Both chemical explanations are highly oversimplified, and to my knowledge, are still completely hypothetical.
3 days ago
Both chemical explanations are highly oversimplified, and to my knowledge, are still completely hypothetical.
It's certainly true that simply explaining it in terms of "neurotransmitter levels" is an oversimplification. ADHD is a neurodevelopmental disorder which is predominantly genetic in origin. In other words, ADHD is not just a matter of the brain's state at the time of diagnosis, but the development of the brain from the very beginning. Brain structure is heavily involved here. It's been shown that prefrontal cortex is significantly smaller in ADHD, along with certain other brain regions, like the hippocampus.
But the implication of neurotransmitters in causing ADHD is not merely hypothetical. ADHD is polygenic, i.e involving many sifferent genes. But in genetic studies, many of the genes found to he most correlated with ADHD were directly involved in monoamine neurotransmission, and many of those relate to dopamine. These include the genes for the D4 and D5 receptors, the dopamine transporter(DAT), which is responsible for dopamine reuptake(and also one of the targets for ritalin), TAAR1, which regulates synaptic monoamine release(this is targeted by amphetamine), and various enzymes involved in monoamine metabolism or synthesis(MAO-A, COMT, DBH).
There's also some involvement of serotonin and noradrenaline related genes like SERT, the serotonin 1b receptor(which, big surprise, is involved in mediating dopamine in PFC), the adrenergic alpha 2a receptor(which is targeted by the adhd meds clonidine and guanfacine), and some more enzymes.
So the genetic evidence for the involvement of dopamine is quite strong. There's also some evidence from brain imaging studies, showing that long-term treatment with central stimulants(which primarily act on dopamine and noradrenaline) leads to reduced abnormalities in brain structure. In addition there's mountains of evidence for the effectiveness of stimulants in managing the symptoms of ADHD.
In conclusion, the role of dopamine ADHD is backed up by a lot of empirical data. Doesn't make it the only factor involved, but it's certainly an important one, and not merely hypothetical.
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