By 2050, the number of people with dementia globally will be over 139 million, according to Alzheimer’s Disease International. A new study shows that dementia patients who are on antidepressants, especially selective serotonin reuptake inhibitors (SSRIs), over time may experience faster cognitive decline.

“To our knowledge, this is the first systematic assessment of the long-term effects of commonly used antidepressants on cognition in patients with dementia,” wrote co-corresponding authors Sara Garcia‑Ptacek and Minjia Mo, along with a research team affiliated with Karolinska Institutet and Sahlgrenska University Hospital in Gothenburg.

What Are SSRIs?

Selective serotonin reuptake inhibitors, or SSRIs, are a commonly prescribed class of drugs approved by the U.S. Food and Drug Administration (FDA) to treat depression. The first commercially available SSRI called Prozac was co-invented by Klaus Schmiegel and Bryan Molloy and introduced in the U.S. market in 1988 according to the National Inventors Hall of Fame.

SSRIs work by blocking brain cells from the reuptake of the neurotransmitter serotonin after a signal is transmitted between neurons, which in turn increases the serotonin levels in the brain. Neurotransmitters are chemicals that carry signals between the brain’s nerve cells or neurons. The way it works is that one neuron will secrete a neurotransmitter that is taken up by the receptors on another neuron after the message is delivered. If these receptors are prevented from the reuptake, more neurotransmitters are active in the brain.

What Is Dementia?

By 2050, an estimated 139 million people will be living with dementia worldwide, which is a significant increase from the more than 55 million people who live with dementia currently per Alzheimer’s Disease International. Dementia is a not a single disease, but rather a broad term for a group of symptoms due to brain disorders that affect memory, thinking, emotion, and behavior. Alzheimer’s disease is the most common form of dementia that affects up to 60% of people with dementia, according to Alzheimer’s Disease International.

Why Are Antidepressants Prescribed to Dementia Patients?

“Antidepressants are widely used in patients with dementia to improve neuropsychiatric symptoms, such as anxiety, depression, aggression, and sleep disorders,” wrote the researchers.

According to the study authors, an area that is lacking in research is how antidepressants impact cognitive function in those with dementia despite their association with psychiatric symptoms.

The researchers conducted a national cohort study and used information from over 18,700 dementia patients in the Swedish Registry for Cognitive/Dementia Disorders (SveDem) database over the period of May 2007 to October 2018, where a little over 4,200 had at least one antidepressant prescription. Out of the over 11,900 antidepressant prescriptions issued, a majority (64.8%) consisted of SSRIs.

“In this cohort study, current antidepressant use was associated with faster cognitive decline; furthermore, higher dispensed doses of SSRIs were associated with higher risk for severe dementia, fractures, and all-cause mortality,” the researchers reported.

According to the scientists, three SSRIs (escitalopram, sertraline, citalopram) and one NaSSA (noradrenergic and specific serotonergic antidepressant) called mirtazapine were associated with faster cognitive decline, and the association was stronger in those suffering from severe dementia compared to those with dementia who are not using antidepressants.

The scientists point out that further research is required to understand if the cognitive decline was caused by the depressive symptoms or the antidepressants. What the study clearly demonstrates is that over time, antidepressants were associated with increased cognitive deterioration.

“These findings highlight the significance of careful and regular monitoring to assess the risks and benefits of different antidepressants use in patients with dementia,” the scientists concluded.

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