Abstract Body

Background and purpose

Existing evidence suggests increased mortality in patients prescribed the antidepressant mirtazapine. This study compared all-cause and cause-specific mortality for patients prescribed mirtazapine versus other antidepressants.

Methods

Data source: English primary care electronic health records provided by the Clinical Practice Research Datalink. Study population: adult patients diagnosed with depression who were first prescribed a selective serotonin reuptake inhibitor (SSRI) and then prescribed mirtazapine, a different SSRI, amitriptyline, or venlafaxine. Time window: 01 January 2005 – 30 November 2018. Outcomes: all-cause mortality and mortality due to cardiovascular disease, cancer, or respiratory disease. Analyses: age-sex standardised mortality rates were calculated and survival analyses were performed to calculate hazard ratios (HRs). Propensity score weighting was used to account for patient characteristics.

Results

The study included 25,598 patients and there were 599 deaths. The mirtazapine group had the highest standardised all-cause mortality rate (21.6 deaths/1000 person-years) and the SSRI group the lowest (13.8 deaths/1000 person-years). Over two years of follow-up the mirtazapine group had a higher risk of all-cause mortality than the SSRI group (HR 1.62 [95% confidence interval: 1.28-2.06]), but a similar risk to the amitriptyline (HR 1.18 [0.85-1.63]) and venlafaxine (HR 1.11 [0.60-2.05]) groups. A similar pattern was found for deaths due to cancer and respiratory disease.

Conclusions

There was an increased mortality risk in patients prescribed mirtazapine compared to those prescribed an SSRI. This could reflect residual differences in patient characteristics. Patients prescribed mirtazapine, or other non-SSRI antidepressants, may need support to identify additional health risks and improve their outcomes.