The chemical dopamine plays a critical role in Parkinson’s disease.
It is also involved with the condition Attention deficit hyperactivity disorder, and recently researchers have been looking at whether there are any links between the two.
In today’s post we will look at what Attention deficit hyperactivity disorder is, how it relates to Parkinson’s disease, and what new research means for the community.
Source: Huffington Post
We really have little idea about how Parkinson’s disease actually develops.
It could be kicked off by a virus or environmental factors or genetics…or perhaps a combination of these. We really don’t know, and it could vary from person to person.
There is a lot of speculation, however, as to what additional conditions could make one susceptible to Parkinson’s disease, even those conditions with early developmental onsets, such as autism (which we have previously written about – click here to see that post).
Recently researchers in Germany have asked if there is any connections between Parkinson’s and ADHD?
What is ADHD?
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental condition that begins in childhood and persists into adulthood in 60% of affected individuals.
It is classically characterised in the media by hyperactive children who struggle to concentrate and stay focused on what they are doing. They are often treated with drugs such as Methylphenidate (also known as ritalin). Methylphenidate acts by blocking a protein called the dopamine transporter, which is involved with reabsorbing the chemical dopamine back into the cell after it has performed it’s function.
Ritalin. Source: Wikipedia
So are there any connections between ADHD and Parkinson’s disease?
This is an interesting question.
While there have been no reported findings of increased (or decreased) frequency of Parkinson’s disease in people with ADHD (to our knowledge), there are actually several bits of evidence suggesting a connection between the two conditions, such as abnormalities in the substantia nigra:
Title: Structural abnormality of the substantia nigra in children with attention-deficit hyperactivity disorder
Authors: Romanos M, Weise D, Schliesser M, Schecklmann M, Löffler J, Warnke A, Gerlach M, Classen J, Mehler-Wex C.
Journal: J Psychiatry Neurosci. 2010 Jan;35(1):55-8.
PMID: 20040247 (This article is OPEN ACCESS if you would like to read it)
The substantia nigra is a structure in the brain where the dopamine neurons reside. In Parkinson’s disease, the dopamine neurons of the substantia nigra start to degenerate – 50% are lost by the time a person is diagnosed with the condition.
In this study, the researchers used a technique called echogenicity to examine the substantia nigra of 22 children with ADHD and 22 healthy controls. Echogenicity is the ‘ability to bounce an echo’. This sort of assessment measures the return of an ultrasound signal that is aimed at a structure.
The researchers found that the ADHD subjects had a larger substantia nigra area than the healthy controls – which apparently indicates dopamine dysfunction. This finding is similar to results that have been observed in Parkinson’s disease (Click here to read more regarding that study).
Another connection between the two conditions was recent research has shown that genetic variations in the PARK2 gene (also known as Parkin) contribute to the genetic susceptibility to ADHD.
Title: Genome-wide analysis of rare copy number variations reveals PARK2 as a candidate gene for attention-deficit/hyperactivity disorder.
Authors: Jarick I, Volckmar AL, Pütter C, Pechlivanis S, Nguyen TT, Dauvermann MR, Beck S, Albayrak Ö, Scherag S, Gilsbach S, Cichon S, Hoffmann P, Degenhardt F, Nöthen MM, Schreiber S, Wichmann HE, Jöckel KH, Heinrich J, Tiesler CM, Faraone SV, Walitza S, Sinzig J, Freitag C, Meyer J, Herpertz-Dahlmann B, Lehmkuhl G, Renner TJ, Warnke A, Romanos M, Lesch KP, Reif A, Schimmelmann BG, Hebebrand J, Scherag A, Hinney A.
Journal: Mol Psychiatry. 2014 Jan;19(1):115-21.
PMID: 23164820 (This article is OPEN ACCESS if you would like to read it)
There are about 20 genes that have been associated with Parkinson’s disease, and they are referred to as the PARK genes. Approximately 10-20% of people with Parkinson’s disease have a genetic variation in one or more of these PARK genes (we have discussed these before – click here to read that post). PARK2 is a gene called Parkin. Mutations in Parkin can result in an early-onset form of Parkinson’s disease. The Parkin gene produces a protein which plays an important role in removing old or sick mitochondria (we discussed this in our previous post – click here to read that post).
In this report, the researchers conducted a genetic sequencing study on 489 young subjects with ADHD (average age 11 years old) and 1285 control individuals. They replicated the study with a similar sized population of people affected by ADHD and control subjects, and in both studies they found that certain deletions and replications in the Parkin gene influences susceptibility to ADHD – two of the genetic variations were found in 335 of the ADHD cases and none in 2026 healthy controls (from both sets of studies).
So there are are some interesting possible connections between ADHD and Parkinson’s disease.
And what has the recent research from the German scientists found?
In this study, the researchers have looked at additional genetic variations that have been suggested to infer susceptibility to ADHD.
Title: No genetic association between attention-deficit/hyperactivity disorder (ADHD) and Parkinson’s disease in nine ADHD candidate SNPs
Authors: Geissler JM; International Parkinson Disease Genomics Consortium members., Romanos M, Gerlach M, Berg D, Schulte C.
Journal: Atten Defic Hyperact Disord. 2017 Feb 7. doi: 10.1007/s12402-017-0219-8. [Epub ahead of print]
PMID: 28176268
The researchers analysed nine genetic variations in seven genes:
- one variant in the gene synaptosomal-associated protein, 25kDa1 (SNAP25)
- one variant in the gene dopamine transporter (DAT; also known as SLC6A3)
- one variant in the gene dopamine receptor D4 (DRD4)
- one variant in the gene serotonin receptor 1B (HTR1B)
- three mutations in cadherin 13 (CDH13)
- one mutation located within the gene tryptophan hydroxylase 2 (TPH2)
- one mutation located within the gene noradrenaline transporter (SLC6A2)
These genetic variations were assessed in 5333 cases of Parkinson’s disease and 12,019 healthy controls. The researchers found no association between any of the genetic variants and Parkinson’s disease. This finding lead the investigators to conclude that these genetic alterations associated with ADHD do not play a substantial role in increasing the risk of developing Parkinson’s disease.
Have ADHD medications ever been tested in Parkinson’s disease?
Yes.
Given the association of both ADHD and Parkinson’s disease with altered dopamine processing in the brain, a clinical trial of ritalin in Parkinson’s disease was set up and run in 2006 (Click here to read more about that trial). The results of the trial were published in 2007:
Title: Effects of methylphenidate on response to oral levodopa: a double-blind clinical trial.
Authors: Nutt JG, Carter JH, Carlson NE.
Journal: Arch Neurol. 2007 Mar;64(3):319-23.
PMID: 17353373 (This article is OPEN ACCESS if you would like to read it)
In this study, the researchers recruited 12 people with Parkinson’s disease and examined their response to 0.4 mg/kg of ritalin – given 3 times per day – in conjunction with their normal anti-Parkinsonian medication (L-dopa). They then tested the subjects with either ritalin or a placebo control and failed to find any clinically significant augmentation of L-dopa treatment from the co-administration of ritalin.
What does it all mean?
So summing up: both Attention deficit hyperactivity disorder (ADHD) and Parkinson’s disease are associated with changes in the processing of the brain chemical dopamine. There are loose connections between the two conditions, but nothing definitive.
It will be interesting to follow up some of the individuals affected by ADHD, to determine if they ultimately go on to develop Parkinson’s (particularly those with Parkin mutations/genetic variants). But until then, the connection between these two conditions is speculative at best.
The banner for today’s post was sourced from Youtube
The Science of Parkinson's 
Finally, some articles for laymen linking these two conditions! I am a 38-year old female who was recently diagnosed with ADHD (which I suspect I inherited from my mom). My mom is showing some early possible signs of Parkinson’s disease now and I am worried (and I believe my mom is terrified) because her mother–my grandmother– suffered from Parkinson’s for almost 20 years before she passed away. after doing some research I suspected a possible link between ADHD and PD and brought this up to my doctor but he dismissed this idea. I found some schoarly article about a link but it seemed there is a long way to go to truly shed some light on how these two are linked. Thank you for this posting and the list of studies and summary. Greatly comforting. Hope more is found out soon.
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Have you and your mother submitted a DNA sample to 23andMe to determine if either of you carry a PARK mutation? My father had PD, and likely had undiagnosed ADHD. I had my DNA tested for both ancestry and health and learned (a month ago) I have the LRRK2 mutation and about 8 other risk factors for PD. Knowing that I am signing up for clinical trials funded by the Michael J Fox Foundation and doing all I can to reduce variable risk factors. Taking action driven by knowledge of my risk factors is very empowering.
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Hi Reni,
Thanks for your comment and well done for being aware & proactive. It is important to remember, however, that our understanding of the genetics of PD and ADHD is basic at best, and not too much should be read into it. The information we gain from DNA testing is ‘informative’, but in no way absolute. We have a lot of people with numerous LRRK2 genetic variants in the general population that do not go on to develop PD within their life times (even with affected individuals within their immediate family). It is good to be aware of these things, but it does not necessarily mean that one’s life course is already determined. While other neurodegenerative conditions (such as Huntington’s disease) can be pre-diagnosed with a genetic test, we are certainly not there yet (if we ever will be) with the genetics of Parkinson’s. In addition, there is a universe of knowledge awaiting us with regards to the ‘epigenetics’ (the non-genetic factors that influence the impact of our genetics) of Parkinson’s. We have only started to scratch the surface with regards to understanding of that.
All of that said, ‘Go you!’ for getting involved with the research. That is an attitude that I fully respect!
Kind regards,
Simon
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I would note that this study, which came out a couple of years after this article was posted, shows a strong relationship between ADHD and Parkinson’s, and an even stronger relationship between medications given for ADHD and the likelihood of developing Parkinson’s.
https://www.ajmc.com/view/new-research-finds-link-between-adhd-and-parkinson-disease
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Wow. This is crazy.
I recently turned 23 years old. I was diagnosed with severe ADHD 7 months ago.
My moms father had Parkinson’s disease.
My dad’s mother had Parkinson’s and her brother had it as well and just passed away this year after living with the disease for as long as I can remember.
And then I find out – my grandma and great uncle had another sister, and she had Parkinson’s as well.
After HOURS straight of reading about Parkinson’s and ADHD (it is 5:46Am) … I have convinced myself all too much that I’m destined to get this awful disease….
Everything I read on both PD and ADHD Differs. Apparently, no one knows what exactly ADHD is. Ironically, no one knows what exactly Parkinson’s is. The ONE thing that we’re *almost* sure of is that they both are caused by some sort of dopamine dysfunction.
I don’t even know what to think. I definitely don’t feel as sharp minded as I used to be. I religiously take my adderall during the week, yet I truly am not motivated like I once was. My hands have always been a smidge shaky but recently I have started to really notice it. In the last 2 months I have had at least 3 occurrences of half losing my balance for no good reason.
For a few years I have had an occasional random twitch that was not voluntary. I especially noticed it when I smoked weed. But if anything … isn’t weed supposed to suppress Parkinson’s symptoms?
Yes I know, I should clearly stop taking my adderall and see what happens. But also, how the hell am I supposed to focus at work?!?!?!
I have wanted to get my genes tested for some time now but what’s the point if there’s not even a cure? To depress me for the rest of my existance?
I’m stressed. Some insight would be much appreciated.
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Hi Rachel,
Thanks for your comment.
The first and most important thing to do is not to stress. Easier said than done I appreciate, but getting stressed out serves no constructive purpose. Next, it is important to understand that our understanding of the biology of both ADHD and Parkinson’s is still BASIC at best. There is a great deal that we do not know about both of these conditions. This does not mean, however, that we can’t stop//slow PD (we have been using vaccines for a very long time, but only recently have we worked out how they actually work).
Third, as I mentioned in a comment above, genetics and family history are NOT a determinant of future risk of developing either condition. In the case of Parkinson’s, we have numerous cases of individuals who ‘should’ have Parkinson’s according to the genetic variations in their DNA, but they don’t and we do not understand why. The best example of this is an elderly lady in Sydney (Australia) who has multiple PARKIN mutations which usually leads to very early onset PD, but she is yet to be diagnosed – and she is in her 80s (https://scienceofparkinsons.com/2017/10/07/nix/).
The best things to do are speak with your doctor or seek advice from a neurologist with expertise in this area. Next, learn as much as you can about yourself (you could even get involved with research if you like), exercise regularly/eat well, get good quality sleep, and don’t stress. The last one seems to be very important with PD as the case of identical twins suggests (https://scienceofparkinsons.com/2016/07/27/identical-twins-and-parkinsons-disease/). And, of course, stay proactive and informed. As we try to make people aware here on the website, a great deal of new experimental treatments are being developed for PD. And I for one am very optimistic about ability to slow/halt this condition in the near future.
I hope this helps – I am happy to discuss this further.
Kind regards,
Simon
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I would note that this study, which came out a couple of years after this article was posted, shows a strong relationship between ADHD and Parkinson’s, and an even stronger relationship between medications given for ADHD and the likelihood of developing Parkinson’s.
https://www.ajmc.com/view/new-research-finds-link-between-adhd-and-parkinson-disease
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Why does a clinical researcher look to a chemical solution and not a behavioral treatment. Gee it sure would be great it a little medication could cure ADHD and Parkinson’s Disease. It could also be very profitable to the pharma industry. What research has proven is that brain chemistry and structure in the PD patient is different for each patient. I have found that using a high intensity exercise routine 3 days a week have had significant positive results for my PD. I have not found that the attention disorder is a chronic behavioral issue that can be addressed best by following the directions of a “coach”. Unlike PD which is significantly mitigated by levo-dopa medications, the ADHD meds are not able to cure the typical symptoms of ADHD. However if taken in conjunction with a treatment plan of organizational behavioral therapy and long term conditioning, the ADHD can be mitigated. I haven’t heard of a clinical study for PD patients with ADHD. If anyone knows of such a trial or knows of a treatment for these combination of conditions please post.
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Hi Mijoon, Thanks for your message – sorry for taking sooo long to respond to it (not sure how we missed it!). Sorry to hear about your mum, has she seen anyone about it? We would be interested to know what other ‘scholarly articles’ you found regarding the possible connection between these two conditions. It is a very under researched area, and worthy of further investigation.
Glad you liked the post.
Kind regards,
Simon
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Thank you for your kind regards. My mom is decided against seeing a doctor for now, thinking the disruption of her routines and peace of mind outweigh the benefits. I hope I will be able to persuade her to get the help she need soon. With regard to the articles I have found, here are some.
(1) https://www.ncbi.nlm.nih.gov/pubmed/24911152
This paper reports of various scanning, experiments and treatments of a single patient, particularly on two mutations he has in dopamine transporters, one of which the researchers say linked to parkinsonism for the first time. What was interesting to me was how methylphenidate treatment for the patient produced “unacceptable side effects” and how the patient did not feel alleviation of his symptoms. This sounds rather like my own case, and I wonder if what is called ADHD is actually a set of slightly different disorders that should be treated with different drugs, and if one or more of them is more closely related to PD than the others.
(2)
https://www.ncbi.nlm.nih.gov/pubmed/17982908
https://www.ncbi.nlm.nih.gov/pubmed/22470460
These two studies combined made me think twice about what disorder I have and what drug I should take. They suggest that methylphenidate treatment could produce “neurodegenerative consequences and “may be a risk factor for the development of Parkinson’s disease”.
(3)
https://www.ncbi.nlm.nih.gov/pubmed/17197367
This study describes a loose connection between ADHD, PD and schizophrenia. One of my aunts (my mom’s elder sister) has had schizophrenia for almost 50 years, which I heard was triggered by domestic violence of her husband. I also heard that my grandmother was electrified while changing a bulb shortly before she exhibited first PD symptoms. None of her siblings are either alive or diagnosed with one yet, although my mom has stiff joints (comes and goes), slow walk as well as impairment of fine manual control. She can no longer peel apples and her handwriting is bigger and shaky than it was before.
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Hi Lawrence, thanks for your message.
“Why does a clinical researcher look to a chemical solution?” – I think it’s a case of a man with a hammer looks at every problem as a nail. All joking aside, I actually started out in behavioural psychology and still believe strongly in many of the laws of behavioural conditioning. I completely agree with you that a combination of treatment regimes is the best approach to PD and ADHD.
Regarding exercise: something sadly missing on this website is a few post regarding physical exercise, stretching, etc but I’m just not sure where to start. A particular drug is easy to research, but exercise regimes vary so much it is difficult to provide a focused story. If anyone has any ideas, we’d love to hear them.
I am only aware of one clinical trial currently ongoing for PD and attention deficit. It is being conducted by the University of Chicago and it will look at taking a “multidisciplinary approach to manage gait difficulty” in people with Parkinson’s disease. It appears to be focused on combinations of drugs that will hopefully help improve attention as well, but may also have a behavioural component. It could be worth investigating if interested (Click here to read more: https://clinicaltrials.gov/ct2/show/NCT02857244?).
In addition, I have found several other clinical trial results recently regarding ADHD and PD. Most notably (https://www.ncbi.nlm.nih.gov/pubmed/21464430?dopt=Abstract ; the article is available on OPEN ACCESS here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3068005/ ; for details regarding the trial click here: https://clinicaltrials.gov/ct2/show/NCT00526630? ). The investigators were looking at whether methylphenidate could improve gait impairment in PD. It did not. And unfortunately it tended to worsen measures of motor function, sleepiness, and quality of life (and this was a double blind study). So perhaps this treatment should be avoided in folks who think they have a combination of ADHD and PD. I will keep an eye out for any planned clinical trials for PD and ADHD.
I hope all of this helps.
Kind regards,
Simon
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I think it’s hilarious that behavioral practitioners talk about the profits that “big pharma” makes on ADHD drugs.
Where I live, the drugs are $35/month. Weekly therapy, on the other hand, would be over $500/month.
Who’s profiting more?
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Thank you for this explanation.
My Father-in-law has Parkinsons, my husband and daughter both have ADHD, OCD, & occupy some small space on the autism spectrum. My daughter also is showing symptoms of restless leg syndrome, and has an eating disorder. Even stranger, my best friend also has ADHD, and his dad has Parkinsons too.
Considering that dopamine ties Parkinsons, ADHD, and RLS together, I thought their *had* to be a connection somewhere. I wish there was a reliable brain scan that could tell us what was going on. 😦
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Hi XianJaneway,
Thank you for your comment – sorry to hear of your father-in-law’s diagnosis, I hope the medication is working well for him. Currently our understanding of all these conditions is still basic and in need of further research. That said, each week improvements are being made and major steps forward are being taken. It is important to be aware of this and to stay vigilant for signs of new developments. In the case of your husband and daughter having ADHD and OCD, this does not mean that they will go on to develop or have an increased risk of developing PD. There are some associations between the conditions, but only a small fraction of the ADHD community develop PD and only a small fraction of the PD community had ADHD. The information presented here is solely for educational purposes and it not intended to cause anyone one distress.
I hope this helps – happy to discuss further.
Kind regards,
Simon
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After studying what has been written on restless legs syndrome, my own working hypothesis is that it is caused by hypoxia of the leg tissues. There was a very good study of this that showed a strong association between hypoxia and RLS symptoms.
As for the dopamine connection, well, yes, dopamine agonists, by stimulating dopamine receptors in the vasculature, can dilate the vasculature of the legs, thus improving circulation. And improving circulation is one day to bring more oxygen to leg tissues that might otherwise be starving for it, all other things being equal.
But that is certainly not the only way to increase oxygenation of leg tissue. Something as simple as Vicks vaporub applied to the soles of the feet prior to bed time might help by dilating blood vessels local to the application, since eucalyptus, camphor and menthol are all known to have that effect. Or, if the patient has anemia, then remedies for anemia, such as iron supplementation, or B12 and folic acid supplementation, depending on the kind of anemia, might also help to bring more oxygen to the legs by increasing the carrying capacity of the blood for oxygen.
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Hello Simone,
A little background before getting to my main points. First I am currently a Pharm. D student with a bachelors in medicinal chemistry so do not worry about simplifying answers for me. Additionally 3 of the 5 members of my immediate family have been diagnosed with ADHD, 5-10 on my fathers side have been diagnosed with ADHD and 2-10 so far have been diagnosed with early onset parkinson’s, 1-10 has been diagnosed with epilepsy. I was wondering exercise has ever proven beneficial for PD because I know it has been proven benefical for ADHD. Additionally I was wondering if there are any studies which identify genes which correlate with both ADHD and PD. I am currently 25 and would like to do everything I can to prevent a PD diagnosis, and prolong the progression of the disease.
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Hi William,
Thanks for your comment. Sorry to hear about your family’s situation, I hope the treatment medication is helping. And well done for taking a proactive approach – I have a great deal of respect for that. Regarding exercise and PD, I am currently working on a post about this topic so stay tuned for that (it is a complicated topic that has taken longer than expected, but it is in the works). I will link it here when it becomes available, but the take home message of that post will be that exercise is good – there is certainly evidence that suggests particular types of exercise (such as high intensity) are beneficial for people with PD.
The genetic influence for both PD and ADHD is very low (heritability is high in ADHD, but the actual genetic variants determining this is not clear). We talk a lot about genetic variants in PD associated genes like LRRK2 on this blog, but only 1% of the PD affected community actually has a LRRK2 mutation. GBA1 is the most common gene associated with PD, with 10% of the PD community having a GBA1 mutation, but I have never seen any research indicating any link between GBA1 and ADHD.
It is really very difficult to provide information in situations like this, because a.) a lot of background info is missing, and b.) we are talking about two very heterogeneous conditions. While the evidence of what can prevent PD is very grey, there are certain foods that should be avoided (read: https://scienceofparkinsons.com/2017/09/18/food/). I hope this helps.
Kind regards,
Simon
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My dad has Parkinson’s and has recently begun to exhibit very hyper activity. He cannot sit still for very long. He is constantly walking through the house or standing in one spot, focused on something. It is not unusual for him to be on his feet for 5-6 hours without sitting down. While he is walking around the house, he often rummages through drawers, cabinets, etc. He is also getting up several times at night. Do you have any insight on these problems?
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Hi Leah,
Thanks for your message, but – apologies – I’m not a clinician. Just a research scientist. So I really can’t be speculating over the internet as to what could be happening with your father. I would simply recommend you have a chat with his doctor, as they will be aware of his full medical history.
Sorry I can’t help any further.
Kind regards,
Simon
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The University of Utah just released a study last month of possible link between stimulant use (eg, Ritalin for ADHD) and high chance of Parkinson’s. So maybe the genetic link may not be all the story–stimulant use could, too.
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Hi Current Resident,
Thanks for your comment. We have discsussed that study in a more recent post (https://scienceofparkinsons.com/2018/09/14/adhd/). If the association is real (and it needs to be replicated before we can really conclude anything), it appears to be affecting only a very small number of people with ADHD. So there is no need for everyone to panic.
Kind regards,
Simon
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Since this article was written, a study has confirmed the link between ADHD and Parkinson’s.
https://www.ajmc.com/view/new-research-finds-link-between-adhd-and-parkinson-disease
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Seems like a very unintelligent idea to study ritalin as a treatment for Parkinson’s, and I could not be less surprised that the trial failed to show any benefit.
The main symptoms of Parkinson’s stem from a decline in the population of dopamine neurons. Methylphenidate blocks the action of the dopamine transporter, preventing dopamine from being imported into the patient’s surviving dopamine neurons, from which it could then be released under the control of those neurons, which more closely mimics physiological conditions than having that same dopamine left in the inter-cellular space, where it ambiently stimulates dopamine receptors without the guidance offered by those remaining dopamine neurons, and without taking advantage of the ability of those remaining neurons to store and buffer dopamine produced in by the pulsatile dosing of levodopa, which would normally be a factor contributing to the smoothing of the peaks and troughs of the dosing cycle.
So methylphenidate would seem to offer only an additional impairment of normal physiological function. It is surprising that anyone would find it to be worthwhile to test this as a treatment for Parkinson’s.
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