ADHD & PD: The Basal Ganglia and Cerebellum Connection
All Science News articles summarize a research study and are not an official opinion, endorsement or position of the Parkinson’s Foundation’s.
Two parts within our brain require healthy dopamine regulation and transmission to do their jobs:
- The basal ganglia: messengers that sort out information for the spinal cord and cerebellum and are associated with various functions, including motor control, motor learning, executive functions and behaviors, and emotions.
- The cerebellum: involved in movement and coordination, walking, posture, reflexes, and eye and head movement; it also sends instructions to our muscles that adjusts our posture and keeps our bodies moving smoothly.
Adults with attention-deficit hyperactivity disorder (ADHD) have been shown to have damaged dopamine neurons in the basil ganglia, and, commonly have cerebellar abnormalities, much like people with Parkinson’s disease (PD). So, are ADHD and PD somehow connected? Perhaps.
A recently published study in the journal, Neuropsychopharmacology, sought to determine if having ADHD and/or its treatment, increases the risk of having basal ganglia and cerebellar diseases. In this 20-year follow-up retrospective cohort study, a total of 190,586 patient records (31,796 with ADHD and 158,790 without ADHD) from Utah were examined. People with no prior PD diagnosis or symptoms, no basal ganglia/cerebellar disease and those with a history of substance abuse were excluded from participating in the study.
- Overall, ADHD was associated with a 2.4-fold increased risk of basal ganglia and cerebellar (BG&C) diseases.
- Of the people diagnosed with a basal ganglia or cerebellar disease, 96 of non-ADHD (32.3%) and 56 of people with ADHD (33.7%) were diagnosed specifically with Parkinson’s.
- Though the numbers of people with PD in this study was small, a 2.6-fold increased risk of Parkinson’s was observed for people with ADHD compared with non-ADHD (consistent with risk overall of BG&C diseases).
- In people with ADHD who were prescribed stimulant medications, the risk of PD was 4-fold that of people who do not have ADHD.
- Lastly, the risk of young-onset BG&C diseases before age 50 years was increased in people with an ADHD history, particularly in those that were prescribed stimulants.
In terms of comparing people with ADHD to non-ADHD, (for all basal ganglia/cerebellar diseases, not just PD):
- People with ADHD prescribed stimulants were significantly more likely to have BG&C diseases compared to those without ADHD.
- People with ADHD prescribed stimulants were at greater risk of having BG&C diseases compared to than people with ADHD who were not prescribed stimulants.
What Does This Mean?
People with an ADHD diagnosis were shown to have more than 2-fold increased risk of a subsequent diagnosis of BG&C diseases — including and specifically PD — compared to people with no history of ADHD. That 2-fold increased risk includes BG&C diseases such as secondary parkinsonism, other degenerative diseases of the basal ganglia, and essential tremor.
Of particular note, for people on ADHD medication, their risk of PD doubled to 4-fold, compared to people without ADHD. Further, according to the most recent data available from the Centers for Disease Control and Prevention (CDC, 2018), approximately 9.4% of children 2-17 years of age (6.1 million) had ever been diagnosed with ADHD, and almost two thirds (62.0%) were taking medication (Danielson et al., 2018). While results from this study suggest people taking certain ADHD medications may be at an increased risk for earlier-onset BG&C diseases (including PD), this is just a single study, and results have not been replicated. In addition, even with an increase in risk, the overall risk in developing PD is still very small. Always talk to your doctor regarding any health concerns you may have.
The Parkinson’s Foundation believes in empowering the Parkinson’s community through education. Learn more about the connection between ADHD and Parkinson’s in the below Parkinson’s Foundation resources or by calling our free Helpline at 1-800-4PD-INFO (473-4636).