Some 16 million Americans a year struggle with depression, an illness that comes in many forms—from major depression to dysthymia and seasonal affective disorder. In addition, depressive episodes are features of bipolar disorder. Depression is an illness that increasingly afflicts people worldwide, interfering with concentration, motivation, and many other aspects of everyday functioning. It is a complex disorder, involving many systems of the body, including the immune system, either as cause or effect. It disrupts sleep and it interferes with appetite, in some cases causing weight loss, in others weight gain. Because of its complexity, a full understanding of depression has been elusive.
Depression is often accompanied by anxiety. Research indicates that not only do the two condition co-occur but that they overlap in genetic vulnerability patterns.
Scientists have some evidence that depression susceptibility is also related to diet, both directly—through inadequate consumption of nutrients such as omega-3 fats—and indirectly, through the variety of bacteria that populate the gut. Of course, depression involves mood and thoughts as well as the body, and it causes pain for both those with the disorder and those who care about them. Depression is increasingly common in children.
Even in the most severe cases, depression is highly treatable. The condition is often cyclical, and early treatment may prevent or forestall recurrent episodes. Many studies show that the most effective treatment is cognitive behavioral therapy, which addresses problematic thought patterns, with or without the use of antidepressant drugs. In addition, evidence is quickly accumulating that regular mindfulness meditation, on its own or combined with cognitive therapy, can stop depression before it starts by effectively disengaging attention from the repetitive negative thoughts that often set in motion the downward spiral of mood.