The finding:
Adult ADHD is independently associated with an increased risk of Lewy Body Dementia (LBD), any dementia (Alzheimer’s and vascular), and non-amnestic-Mild Cognitive Impairment. Patients with LBD and ADHD were more likely to have cognitive fluctuations, parkinsonism, hyposmia and visual hallucinations. Incidence of depression was significantly higher in the ADHD group.

Strength and weaknesses:
This was a prospective study with a decade long follow-up, thorough initial assessments, strict exclusion criteria (improved specificity), used standardized diagnostic tools and attention to interrater consistency. At the same time, the study included patients who sought treatment for cognitive difficulties (selection bias), did not take vascular risk factors into account and did not include confirmatory pathological studies. Strict exclusion criteria (substance use, pharmacological treatment of ADHD symptoms, evidence of any brain disorder or mental illness) improved specificity but decreased the generalizability of the findings.

Relevance:
Diagnosis of adult ADHD is becoming increasingly more common. There is building evidence connecting adult ADHD symptoms with future risk for neurodegenerative disorders. Given the overlap of symptoms between these two disorders, and the traditional view that these are found in very different age groups, it is important to be acutely aware of their comorbid status. Other comorbidities that accompany ADHD, such as lifestyle choices, reward-seeking behaviors, substance use, and depression, are individual risk factors for dementia. ADHD may be a risk factor, a pre morbid condition or a comorbidity of dementia.