Does having adult ADHD increase dementia risk?

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common mental disorders of childhood, and symptoms include inattention, hyperactivity, and impulsivity. While some children with ADHD outgrow it, it often continues into adulthood. Also, some adults are newly diagnosed with ADHD because a diagnosis is missed during childhood. A recent large observational study reported that getting an ADHD diagnosis in adulthood may be associated with a higher risk of dementia [1].

These findings come from a cohort study including 109,218 people without an ADHD or dementia diagnosis at the start of the study (mean age, 57.7 years old), who were followed for 17.2 years. Information on ADHD and/or dementia diagnosis was collected from electronic health records held at the Meuhedet Healthcare Services, a nonprofit health maintenance organization that provides health care services with national coverage to 14% of the total population of Israel. Analyses were carried out after controlling for many variables that can affect outcomes, such as age, sex, socioeconomic status, smoking status, other health conditions, and the use of psychostimulant medication. 

During the follow-up period, 730 people received a diagnosis of ADHD, and 7,726 people received a diagnosis of dementia. Researchers found that diagnosis of ADHD as an adult was associated with a 2.77-fold higher dementia risk. Interestingly, dementia risk was not significantly higher in people who received an ADHD diagnosis as an adult who also received psychostimulant medications. 

The findings are in line with some of the other literature assessing the relationship between ADHD and dementia, though these types of studies are currently limited, and the extent of the associations are still unclear [2]. Also, because these studies are observational in nature, they are not designed to prove that having ADHD as an adult is a direct cause of dementia. The higher risk of dementia may be partly explained by other risk factors of dementia such as depression, which are more prevalent in people with ADHD than those without [3]. Researchers found that when the analysis was confined to shorter lag times, there was a higher association between ADHD diagnosis and dementia risk, suggesting that there may be some overlap in diagnosis. In other words, someone with undiagnosed dementia may receive an ADHD diagnosis shortly before receiving a dementia diagnosis due to some similarities in symptoms. People with childhood ADHD should not be alarmed, as the current study did not assess whether people who had ADHD in their childhood had elevated risks of developing dementia later in life, as anyone with prior diagnosis of ADHD were excluded from the study [1].

There are different interpretations to the results regarding psychostimulant medications. One possibility is that psychostimulant medications act as cognitive enhancers and reduce dementia risk. Another possibility is that psychostimulants are not directly affecting dementia risk, per se, but that people who are seeking medical treatments for ADHD may also be better managing other conditions that are associated with dementia risk, such as high blood pressure, type 2 diabetes, and depression [4]. A randomized placebo-controlled clinical trial is needed to conclusively determine whether psychostimulant medications may help lower the risk of dementia in people with adult ADHD.

1. Levine SZ, Rotstein A, Kodesh A et al. (2023) Adult Attention-Deficit/Hyperactivity Disorder and the Risk of Dementia. JAMA network open  6, e2338088.
2. Becker S, Chowdhury M, Tavilsup P et al. (2023) Risk of neurodegenerative disease or dementia in adults with attention-deficit/hyperactivity disorder: a systematic review. Frontiers in psychiatry  14, 1158546.
3. Katzman MA, Bilkey TS, Chokka PR et al. (2017) Adult ADHD and comorbid disorders: clinical implications of a dimensional approach. BMC psychiatry  17, 302.
4. Livingston G, Huntley J, Sommerlad A et al. (2020) Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. Lancet  396, 413-446.

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