"Mental pain is less dramatic than physical pain, but it is more common and also more hard to bear...
...The frequent attempt to conceal mental pain increases the burden: it is easier to say “My tooth is aching” than to say “My heart is broken."
- C.S. Lewis, The Problem of Pain
Major Depressive Disorder (MDD) is the most commonly diagnosed mental health disorder, and is commonly just referred to as "Depression." MDD is cyclical, with periods of remission. Some people only experience one episode in their entire life and never have another. But the more of these episodes one experiences, the more likely a repeat episode becomes.
MDD can be incredibly debilitating. The WHO estimates that depression alone is responsible for $1 trillion (USD) in lost productivity yearly world-wide. For individuals, depression can affect mood, appetite, sleep, motivation, pleasure, sex-drive, and of course the will to live.
MDD is also treatable. Studies have shown that Cognitive Behavioral Therapy is just as effective at treating MDD as medication therapies, with fewer side-effects and last past the cessation of therapy. Behavioral Activation is a newer form of CBT which shows particular promise at treating the disease.