Clin Psychopharmacol Neurosci.  2023 Aug;21(3):478-487. 10.9758/cpn.22.991.

Which Severe Mental Illnesses Most Increase the Risk of Developing Dementia? Comparing the Risk of Dementia in Patients with Schizophrenia, Major Depressive Disorder and Bipolar Disorder

Affiliations
  • 1Department of Psychiatry, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
  • 2Department of Psychiatry, National Cheng Kung University Hospital, Dou-Liou Branch, Yunlin, Taiwan
  • 3Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
  • 4Department of Pharmacy, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
  • 5Institute of Clinical Pharmacy and Pharmaceutical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
  • 6Health Outcome Research Center, National Cheng Kung University, Tainan, Taiwan
  • 7Institute of Behavioral Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
  • 8Department of Psychiatry, Tainan Hospital, Ministry of Health and Welfare, Tainan, Taiwan

Abstract


Objective
Previous studies have shown that certain severe mental illnesses (SMIs) increase the risk of dementia, but those that increase the risk to a greater degree in comparison with other SMIs are unknown. Furthermore, physical illnesses may alter the risk of developing dementia, but these cannot be well-controlled.
Methods
Using the Taiwan National Health Insurance Research Database, patients with schizophrenia, bipolar disorder and major depressive disorder (MDD) were recruited. We also recruited normal healthy subjects as the control group. All subjects were aged over 60 years, and the duration of follow-up was from 2008 to 2015. Multiple confounders were adjusted, including physical illnesses and other variables. Use of medications, especially benzodiazepines, was analyzed in a sensitivity analysis.
Results
36,029 subjects (MDD: 23,371, bipolar disorder: 4,883, schizophrenia: 7,775) and 108,084 control subjects were recruited after matching according to age and sex. The results showed that bipolar disorder had the highest hazard ratio (HR) (HR: 2.14, 95% confidence interval [CI]: 1.99−2.30), followed by schizophrenia (HR: 2.06, 95% CI: 1.93−2.19) and MDD (HR: 1.60, 95% CI: 1.51−1.69). The results remained robust after adjusting for covariates, and sensitivity analysis showed similar results. Anxiolytics use did not increase the risk of dementia in any of the three groups of SMI patients.
Conclusion
SMIs increase the risk of dementia, and among them, bipolar disorder confers the greatest risk of developing dementia. Anxiolytics may not increase the risk of developing dementia in patients with an SMI, but still need to be used with caution in clinical practices.

Keyword

Dementias; Bipolar disorder; Benzodiazepine; Major depressive disorder; Schizophrenia
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