Imagine a man accused of wrongdoing who cannot even remember his own name, or a woman in her fifties repeatedly violating traffic laws without realizing the seriousness of her actions. Should such cases be brought to court?
And how should society handle people who commit acts of aggression without truly intending harm?
These questions highlight a little-known but important issue: the link between dementia and criminal behavior.
Neurodegenerative diseases, such as Alzheimer’s disease, frontotemporal dementia, and Parkinson’s disease, affect different parts of the brain.
While Alzheimer’s is best known for memory loss, other forms can alter behavior, emotions, and even impulse control.
In some cases, changes in the brain may lead individuals to commit acts they never would have considered before, such as harassment, theft, property damage, or even aggression toward others. For families, these behaviors can be deeply distressing, and for society, they raise difficult legal and ethical questions.
To better understand this phenomenon, researchers Matthias Schroeter and Lena Szabo from the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) conducted a large meta-analysis, combining data from 14 studies involving more than 236,000 people across several countries, including the U.S., Sweden, Finland, Germany, and Japan.
Their findings, published in Translational Psychiatry, show that criminal risk behavior is more common in the early stages of dementia than in the general population—but tends to decline later in the disease as cognitive function deteriorates further.
The researchers noted that criminal behavior appearing for the first time in midlife could be an early warning sign of dementia, suggesting the need for rapid diagnosis and treatment.
They found that the risk of such behavior was highest in people with behavioral variant frontotemporal dementia (over 50%) and semantic variant primary progressive aphasia (40%).
By contrast, it was much lower in vascular dementia and Huntington’s disease (around 15%), in Alzheimer’s disease (10%), and lowest in Parkinsonian syndromes (under 10%).
In a second study, published in Human Brain Mapping, the team identified brain changes linked to criminal behavior in frontotemporal dementia. They found greater atrophy in the temporal lobe, a brain region involved in impulse control and decision-making. This suggests that “disinhibition”—the loss of normal social restraints—may drive impulsive or inappropriate behavior in these patients.
While the findings are striking, Schroeter cautions against overgeneralizing. Most offenses linked to dementia are minor, such as traffic violations, indecent behavior, or small thefts, though in some cases aggression or violence can occur. Importantly, many of these individuals have no prior criminal record.
The researchers stress the need for early recognition of such behaviors as possible signs of dementia, alongside prompt medical care.
They also raise the question of whether legal systems should adapt to better account for crimes influenced by neurodegenerative disease.
Greater awareness could prevent unnecessary stigmatization while ensuring fair treatment for patients whose actions are shaped not by malice, but by illness.
If you care about brain health, please read studies about inflammation that may actually slow down cognitive decline in older people, and low vitamin D may speed up cognitive decline.
For more health information, please see recent studies about common exercises that could protect against cognitive decline, and results showing this MIND diet may protect your cognitive function, prevent dementia.
