Dementia is typically associated with severe loss of memory and cognitive function. It's often accompanied by a variety of other psychiatric symptoms, such as anxiety, sleep loss, and depression.

A new population-based study led by researchers from the Karolinska Institute in Sweden has found a common first-line class of medications prescribed to dementia patients for depression could be hastening their cognitive decline, while also putting individuals at greater risk of fractures and earlier death.

Though other factors can't be conclusively ruled out, the possibility that some antidepressants might worsen an underlying condition may be important for medical specialists treating dementia patients to consider.

Selective serotonin reuptake inhibitors (SSRIs) and serotonin norepinephrine reuptake inhibitors (SNRIs) are considered the first choice in antidepressants thanks to having relatively few side effects. Yet recent research has identified an association between the inhibitors and an increased risk of dementia in older adults, compared with psychotherapy.

It's unsurprising that some classes of antidepressants risk interfering with processes responsible for our ability to think and recall our past. However, SSRIs have been considered to be largely helpful in protecting brains from neurodegeneration, even linked to reducing plaques thought to play a role in damaging brain cells.

Reconciling these seemingly contradictory findings in the population has itself failed to reveal a definitive answer, potentially because of the type of data collected and limitations in the way results were gathered.

For their comprehensive analysis, Karolinska Institute neurobiologist Minjia Mo and colleagues used a nationwide Swedish register of medical data collected from newly diagnosed dementia patients between 2007 and 2018. A total of 18,740 patients were included, with just over 20 per cent being recently prescribed at least one antidepressant.

Of those individual drug prescriptions, just under two-thirds were some form of SSRI.

The team found a clear relationship between that medication and severe dementia, with anything more than a standard daily dose predicting an increase of nearly half a point in dementia assessment scores per year.

Given the observational nature of the study and its inherent limitations, it's plausible that other factors could be influencing the relationship, making it difficult to draw a clear line between the antidepressant dose and cognitive decline.

The fact patients are already experiencing cognitive decline makes the outcome especially challenging to analyse.

However, the researchers also found a concerning rise in the risk of fractures that could be associated with higher SSRI doses, which may indicate unwanted neurological interference too, as do their results hinting at an increase in all-cause mortality.

The study failed to find any such link with SNRIs, suggesting differences in their mechanisms or possibly a limitation in the study itself. Future research could provide clarity on the risks and benefits of each class of antidepressant.

It's important to note changes to medication must only be undertaken in consultation with a doctor. Physicians and specialists in dementia care take a variety of risks and potential benefits into account when prescribing individual patients with a treatment plan and when modifying it.

Tailoring combinations of medication and dosages means considering their overall prognosis, making studies like these essential in striking the right balance in easing the anguish that comes with cognitive decline.

This research was published in BMC Medicine.