Researchers have found that feeling lonely in childhood can accelerate cognitive decline and dramatically increase the risk of dementia later in life.
A major international study has revealed that adults aged 50 and older who experienced frequent loneliness or a lack of close friends in childhood face significantly higher rates of cognitive decline.
Crucially, the emotional experience of loneliness, rather than the actual absence of friendships, proved to be the most powerful driver of dementia risk.
The researchers noted that people who felt lonely as children entered midlife with poorer memory and weaker thinking skills compared to those who did not.
Their cognitive abilities also deteriorated more quickly with each passing year. Even if loneliness fades in adulthood, its imprint may persist for decades.
@doctor.bing Is loneliness bad for your brain? #brain #neurology #brainhealth #neurologist #introvert #lonely #neuroscience ♬ original sound – Dr. Bing, MD MPH
The study, conducted by scientists from universities in China, Australia and the United States, including Harvard and Boston University, analysed data from 13,592 Chinese adults who were tracked over seven years.
Participants completed repeated cognitive tests, enabling the team to measure changes in memory and thinking, and identify who later developed dementia. The findings were published in JAMA Network Open.
The researchers defined “childhood loneliness” as frequently feeling lonely alongside having no close friend.
Those who recalled both loneliness and the absence of close friends were found to have a 41% higher risk of developing dementia later in life.
The effects were even more striking among participants who reported often feeling lonely: they faced a 51% increased dementia risk, even if some did have a close friend.
By comparison, adults who had a close friend in childhood but did not report feeling lonely showed no significant increase in risk.
Importantly, the association between early loneliness and dementia remained strong even among adults who no longer felt lonely, suggesting that the stress of childhood isolation can leave long term damage on brain health.
Childhood is a period of intense neurological growth, and the developing brain is particularly vulnerable to stressors such as loneliness, poverty, food insecurity, neglect and bullying.
Loneliness acts as a chronic brain stressor
Scientists say it floods the brain with harmful hormones that can disrupt the development of vital memory centres. At the same time, it deprives children of the cognitive stimulation gained through social play – a key ingredient for building strong neural networks for reasoning, memory and problem-solving.
The findings add to a growing body of evidence linking early trauma to poor cognitive outcomes later in life.
A separate 2024 study involving more than 10,000 older adults found that childhood hardships such as poverty, unstable home environments and parental addiction were tied to poorer cognitive functioning in later years.
Loneliness in children is increasing
Recent data shows that 64% of girls aged five to seven, 67% of girls aged eight to 10, and a striking 73% of girls aged 11 to 13 reported feeling lonely last year.
With loneliness now recognised as a major public health concern, experts say these findings highlight the urgent need to support children’s emotional wellbeing and social development, not only for their mental health today, but for their cognitive health decades into the future.
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