A recent case-control study evaluated the effects of antidepressant drug classes and individual compounds with different treatment durations on the risk of developing dementia.

It used data from the German Disease Analyzer database and included 62,317 subjects with an incident dementia diagnosis and controls matched by age, sex, and physician. It performed Logistic regression analyses adjusting for health insurance status and comorbid diseases associated with dementia or antidepressant use to investigate the association between dementia incidence and treatment with four major antidepressant drug classes and 14 most frequently prescribed individual substances.

17 of 18 comparisons showed that long-term treatment (≥ 2 years) with any antidepressant is associated with a lower incidence of dementia than short-term treatment. Tricyclic and herbal antidepressants are associated with a decrease in dementia incidence, particularly with long-term treatment. Long-term treatment with escitalopram and Hypericum perforatum possess the lowest risks for dementia on an individual substance basis.

Thus, Long-term treatment with tricyclic antidepressants, Hypericum perforatum, or escitalopram shows the least incidence of dementia. 

Hence, the physician can continue antidepressant therapy for relapse prevention if the patient tolerates it well, even if depressive symptoms have resolved. 

The Journal of clinical Psychiatry. https://www.psychiatrist.com/jcp/neurologic/dementia/long-term-antidepressant-treatment-and-risk-of-dementia/?CLICK=1