‘Having depression may nearly double the risk of developing dementia later in life,’ reported BBC News. It said that a 17-year study of nearly 1,000 elderly people found that 22% of those who were depressed at the start went on to develop dementia, compared with 17% of those who were not depressed.
This is a well-designed study and was accurately reported by the BBC. It has several strengths and adds to the evidence of a link between the two conditions.
However, as the researchers say, this does not necessarily mean that depression causes dementia and the reason for the association between the two conditions is still unclear. It is unknown if depression is a risk factor for dementia, whether it is an early sign of cognitive decline or if certain changes in the brain are associated with both conditions. Also, certain lifestyle factors were not measured by this study, such as poor diet, lack of physical activity and social interaction, and these may increase the risk