The study looked at 1.7 million New Zealanders born between 1928 and 1967 and followed them for 30 years. Those studied were 21-60 at the beginning and 51-90 by the end. The study covered a range of mental health conditions, affecting 4% of those studied. This included self-harm, substance use disorders, mood and neurotic disorders and psychotic disorders. Research found that mental health predicts dementia more strongly than physical health.

The interface between dementia and mental health

Professor Barry Milne, University of Auckland social scientist associate and a co-author of the study, said that this discovery was unexpected:

“This suggests that if we can focus our resources on mental disorders when they peak in adolescence and young adulthood, we may also prevent or delay later dementia.”

Dementia is a term used to describe a range of conditions affecting the brain, including memory, thoughts, and language difficulties. It is caused when the brain is damaged by diseases such as Alzheimer’s or by a series of strokes. It mainly affects people over the age of 65, with an estimated 850,000 people in the UK affected. The NHS has identified dementia as ‘one of the most important health and care issues facing the world’, emphasising the study’s importance. Dementia affects everyone differently and therefore it is vital to consider factors that could prevent it from developing.

Commenting on the shared genetics in both dementia and mental health problems, Dr Milne said that life-long brain vulnerability may be manifesting itself as mental health problems at an earlier stage of life, and dementia later on. However, although the risk for people who have experienced mental health problems is significantly greater, most won’t develop dementia, he said:

“Mental health problems are not ‘life sentences’ that always result in dementia. The reasons behind the connection between early mental health issues and later dementia ‘hasn’t been definitely established’, meaning that although this is a risk of later developing dementia, it is not the only possible factor. Alcohol use and medication for mental disorders such as antipsychotics, could also raise the risk.”