Dementia and mental health conditions such as depression and anxiety have long been closely linked.

Specialized screening tools exist to distinguish depression from dementia, largely because, as neuroscientist Dean Burnett explained in BBC Science Focus, someone who is unable to answer questions cognitively can appear the same as someone who lacks the motivation to respond.

Following a dementia diagnosis - or even the awareness of its possibility - persistent low mood is often unavoidable. However, recent research suggests that repeated patterns of negative thinking, described as a “fatalistic attitude,” may contribute to an earlier onset of dementia or worsen its symptoms.

So how might a negative mindset translate into physical changes in the brain?

While there is no definitive proof that negative thinking directly damages the brain, one likely pathway is through the body’s stress response. Burnett notes that a healthy human brain naturally leans toward optimism - we tend to believe things will work out, that fairness matters, and that our efforts will pay off.

This optimistic bias helps maintain motivation and prevents excessive rumination. According to Burnett, it acts as a psychological defense mechanism.

When this positivity fades, as commonly seen in depression, negative thoughts intensify and stress levels rise. The chemical processes triggered by prolonged stress are known to place biological strain on the brain, which can contribute to various mental health disorders.

If the brain is already vulnerable due to conditions associated with dementia, sustained negative thinking could plausibly accelerate the progression of the disease and intensify its effects.