Everyone feels depressed once in a while for a variety of reasons, but major depression is a potentially serious condition that requires professional help. If you do have major depression, you’ll have a 30% chance of having heart disease in your lifetime. This was reported in a recent issue of Archives of General Psychiatry. The reverse was even more striking: Having heart disease increases your lifetime risk of developing major depression by three fold.
Doctors have known about the association between heart disease and major depression since the early 20th century, but there’s still no good explanation as to what the link is and what causes what.
The problem with these type of studies is that it’s assumed that one must cause the other, but scientific studies by definition can’t look at the big picture and say, perhaps there’s something else that’s causing both major depression and heart disease. That something is obstructive sleep apnea. There are tomes of studies showing that untreated sleep apnea can cause or aggravate both major depression AND heart disease. Treating obstructive sleep apnea can prevent heart disease and depression. What then, causes obstructive sleep apnea? I answer this question at length in my book, Sleep, Interrupted.
Another example of not seeing the forest from the trees.