Loneliness is something most of us will experience at some point. It is a normal emotion, not a character flaw. But it is also something that can quietly affect how we think and remember, and researchers have long debated whether it might even raise the risk of dementia.

A new study, published in [the journal] Aging and Mental Health, suggests the picture is more complicated than either side of that debate has allowed for.

First, it is worth being clear about what dementia actually is. It is not a single diagnosis but an umbrella term covering a range of conditions — the most familiar being Alzheimer's disease — that cause memory loss, confusion, difficulties with language and a gradual loss of independence.

Cognitive decline, meaning a general slowing or weakening of mental function, is not the same thing. The two terms are often used interchangeably, but they should not be: you can experience cognitive decline without ever developing dementia.

We do not fully understand what causes Alzheimer's. We know that a healthy lifestyle lowers the risk, but it is no guarantee. Plenty of people who have done everything right still develop it. The disease is shaped by genetics, aging and biological factors we are still working to understand.

The new study followed just over 10,000 adults aged between 65 and 94 over six years. All were in good health at the outset, fully independent and free of dementia. Researchers tracked their memory over that period and asked whether loneliness played a role in how it changed.

The answer was nuanced.