A Harvard study in May of 2012 reviewed the records of more than 10,000 patients admitted to the ICU and found that if they were on antidepressants that their risk of dying was 73% higher. They also found that 17% of these patients were on SSRI or SNRI antidepressants! This risk remained elevated for one year after discharge. People with acute coronary syndrome or who had heart surgery were more than 200% higher risk of dying!
This retrospective study showed an association, not a clear cause. It is possible that depression itself could have been the underlying issue. We know that how we feel profoundly affects our biochemistry and physiology.