Depression is a known risk factor for heart disease. However, researchers have uncovered a direct link between depression diagnosis and mortality in patients with coronary artery disease (CAD). 
In a study published in the European Heart Journal – Quality of Care and Clinical Outcomes data from 24,137 patients with CAD was analysed, and it was determined not only if they had a diagnosis of depression but also the length of time between CAD and depression diagnosis.
In this study, over 15 per cent (3646) were diagnosed with depression during CAD follow-up. These patients were younger, more likely to be female and diabetic, but were less likely to present with myocardial infarction. 
Researchers summarised that post-CAD depression was ‘the strongest predictor of death,’ including in patients with no prior diagnosis of depression.  Furthermore, the risk of CVD continued to be high more than one year after CAD.
Lead researcher, Dr Heidi May from the Intermountain Medical Centre Heart Institute tells Medical News Today that: “…if you have heart disease and depression and it’s not appropriately treated in a timely fashion, it’s not a good thing for your long-term well-being.” 
This study did not look at how a post-CAD depression diagnosis increased the risk of mortality, however Dr May says that: “We know people with depression tend to be less compliant with medication on average and probably, in general, aren’t following healthier diets or exercise regimens.”  Furthermore, there may be underlying pathophysiological mechanisms at play.
Of course, the link between depression and heart disease has been well documented. Earlier this year a major international study, published in World Psychiatry showed that people with severe mental illness, including major depression, have an 85 per cent higher risk of dying from CVD than the general population. 
This comprehensive meta-analysis of severe mental illness and CVD analysed data from 3.2 million patients and over 113 million people from the general population – including 92 studies covering four continents. Of these, 11.7 per cent of people with major depression had CVD.
Study lead Dr Brendan Stubbs from King’s College London stated in a press release that: “People with SMI die much earlier than those without these disorders, yet the majority of these premature deaths may be preventable with care that prioritises lifestyle changes, such as exercise, better nutrition and stopping smoking, along with cautious prescribing of antipsychotics.” 
And as Dr. Heidi May tells Medical News Today, “I hope the takeaway is this: it doesn’t matter how long it’s been since the patient was diagnosed with coronary artery disease. Continued screening for depression needs to occur […] After 1 year, it doesn’t mean they’re out of the woods.”