The mind-body connection is more than just the fact that your mind exists within your body. Researchers are discovering more every day about how the two interact.
Researchers are now learning that cardiovascular health problems might be related to depression. A recent study found that having poor heart health as an older teenager was linked to developing serious depression as an adult.
Having poor cardiovascular fitness at age 18 made men twice as likely to be admitted to the hospital as an adult for severe depression.
The study, led by Maria A. I. Åberg, MD, PhD, from the Center for Brain Repair and Rehabilitation at University of Gothenburg in Sweden, looked at possible links between a person's cardiovascular fitness at age 18 and future mental disorders. The study involved over one million Swedish men (1,117,292 total) who had served in the Swedish army.
They included a wide range of generations, from those born from 1950 up to 1987, and were followed from three to 40 years. Men who has a psychiatric diagnosis or symptoms of a mental disorder at conscription were not included in the study.
The researchers compared the men's cardiovascular fitness at age 18, when they joined the army, with national health registries to learn which men later developed depression or bipolar disorder.
The researchers found that men with poor cardiovascular fitness were about twice as likely to develop major depression – requiring inpatient admission – at some point later in their adult life.
There was not a similar link for bipolar disorder, which did not appear to pose a higher risk for men whose cardiovascular fitness was low at age 18.
This association remained after the researchers took into account geographical differences, parents' educational level and body mass index (BMI) of the men.
The poorer the men's cardiovascular fitness was at age 18, the more likely it was that they would develop depression.
For example, among the 836 men who scored a 1 (the lowest on the scale of 1-9) on their cardiovascular fitness at age 18, 2.03 percent of them were later admitted for depression.
Similarly, 2.03 percent of those scoring a 2 and 1.97 percent of those scoring a 3 were later admitted for depression.
However, among the 203,522 men who scored a 9 (highest) on cardiovascular fitness, 0.94 percent were later admitted for depression. Among those receiving an 8, only 0.83 percent were admitted for depression, and only 1.01 percent of those who received a 7 later developed severe depression.
The men's cardiovascular fitness at age 18 had been assessed using the cycle ergonometric test. In this test, individuals are given an electrocardiogram (ECG) test at rest and then spend five minutes cycling at a rate of 60 to 70 rpm, as the resistance level is gradually increased, until they choose to stop out of exhaustion.
Their heart rate is measured during this exercise and then calculated with their body mass to determine their cardiovascular fitness level, classified as low (poor), medium or high (good). The men's muscle strength was also tested.
The researchers noted that these results "strengthen the theory" that poor cardiovascular health may contribute to possible causes of depression.
However, their study was limited by the inability to look at some factors that might be affecting the data by contributing to both depression and cardiovascular disease. They called for more research into whether exercise might reduce the risk of depression.
The study was published in the November issue of the British Journal of Psychiatry. The research was funded by the Märtha Lundqvists Stiftelse, the Swedish Research Council for Worklife and Social Science and the Swedish government under the LUA/ALF agreement for biomedical research. No conflicts of interest were noted.