Chinese scientists have found that people with depression are more than twice as likely to develop any form of dementia. At the same time, the risk of Alzheimer’s disease increases fivefold, while the risk of vascular dementia rises by about 1.9 times. The findings were published in the journal Psychiatry Research (PsyRes).

The researchers analyzed electronic medical records from the city of Yichang in China, covering more than 900,000 residents. They selected individuals over the age of 50 who did not have dementia at the start of the study. The final analysis included 4,341 people with depression and more than 43,000 participants without this diagnosis, matched by age and sex.

Over an average follow-up period of about 3.6 years, dementia was diagnosed in 1,493 individuals. The average age at diagnosis was 78 years. The highest risk was observed among people over 60 who had been diagnosed with depression.

Additional analysis revealed a pattern: the risk of Alzheimer’s disease sharply increased during two periods — within the first two years after a depression diagnosis and again after six to eight years. Scientists suggest that different mechanisms may explain this.

In the first case, depression may be an early symptom of already developing Alzheimer’s disease. In the second, prolonged depression may contribute to brain damage due to chronic stress and immune system dysfunction.

For vascular dementia, such an early spike in risk was not observed — the likelihood of the disease increased mainly with long-term depression lasting several years.