Several months ago, I heard on the radio that depression is not simply caused by low levels of serotonin in the brain. This is a canard, embraced by people that yearn for simple solutions to questions that are complex and mysterious. And of course, the prescription drug industry loves the theory because they sell zillions of pills. Researchers don't know if low levels of serotonin cause depression or whether depression causes serotonin levels to drop. Correlation and causality are two very different things.
Depression is caused by a mix of factors – biological, genetic, and environmental. I am feeling more confident in my own theory that the only way to combat this problem is through discipline and force of will. Taking care of your physical self, doing things that are good for you when you don’t feel happy, and refusing to be defeated by negative emotions – that is the path. It isn’t an easy path. The negative emotions may never go away. The fight will continue for as long as you live - every day, every minute. It is daunting, but it is the only way. Talk therapy, medication, exercise, meditation, a sustainable life structure, pursuit of passionate interests, the human touch – these are the tools. But they don’t cure a damned thing. They just keep the beast outside, growling and scratching at the door, instead of inside, creating terror and sadness. And when the beast gets inside, don't panic! Tolerate the misery, and use the tools. Soon, the beast will be outside the door again. The good news about depression is if you fight it, you will win - eventually.
I laugh when it is suggested that depression is a sign of weakness. Depressed people have to be much stronger and resilient than people that aren't afflicted with the disease in order to function; to even stay alive.