Research suggests that being diagnosed with a cardiovascular disease (CVD), such as a stroke or heart attack, may increase a person’s risk of developing a mental health condition. However, it remains unclear whether being diagnosed with a CVD actually causes mental illness, because previous studies have not fully accounted for other factors that might explain the relationship between the two conditions (e.g. the presence of a pre-existing mental illness). Furthermore, research from CoMorMent and other groups has found that certain genes can increase the risk of both CVD and mental illness. This makes it difficult for researchers to tell whether mental illness following CVD is a consequence of CVD or if it was simply by chance that a patient with this genetic pattern experienced CVD first and mental illness second.
With this in mind, a group of CoMorMent researchers led by Qing Shen designed a study to test whether a diagnosis of CVD was related to a subsequent diagnosis of mental illness after other possible explanations were taken into account. To do this they used the Swedish Patient Register, a nationwide collection of electronic health care records. This register contains information on all the inpatient and outpatient visits made by residents in Sweden over many years. The researchers identified all the individuals who had a newly diagnosed CVD and no history of pre-existing mental illness. They then matched these individuals’ health records up with the health records from their unaffected full siblings, and also with the health records from a set of randomly selected individuals in the general population. This allowed the researchers to examine whether the patients with CVD were more likely to develop mental illness than people who had not been diagnosed with CVD.
The researchers found that being diagnosed with CVD did increase a person’s risk of being diagnosed with a subsequent mental illness. This risk of mental illness was particularly high in the months immediately after a CVD diagnosis, and came down as time went on. People with CVD were 2.74 times more likely than their unaffected siblings to develop a mental illness in the first year after they were diagnosed with a CVD. After this first year they were 1.45 times more likely to develop mental illness than their siblings, indicating that the risk of post-CVD mental illness came down over time but did not disappear. The researchers also found similar risk increases when comparing CVD patients to the unrelated general population, meaning that the genetics and environment shared between siblings did not explain the positive relationship. People with multiple cardiovascular conditions were at higher risk of mental illness than those with only one cardiovascular condition. Finally, those who developed a mental illness following a diagnosis of CVD were 55% more likely to die from cardiovascular causes than those CVD patients who had not developed a mental illness.
Health professionals should be aware of the heightened risk of mental illness among people with CVD, especially in the first year after a CVD diagnosis. Clinicians should monitor their CVD patients for the emergence of mental illness and ensure that it is treated promptly. This could help people with CVD to live longer and fuller lives.
