These of some but not all of the symptoms that people deal with that seem to be directly connected to their depression: loss of memory and concentration, pain in the body, chronic pain in neck and shoulder, severe pain in limbs, loss of strength in limbs, inability to use limbs, uclers, indigestion, irritable bowel syndrome, rashes, constipation, gas, weight loss, weight gain, loss of appetite, sleep disruption, inability to stay awake. There are many other symptoms of depression that seem directly linked to depression. as one person said, "when the depression goes up, the pain goes down. when the pain goes up, the depression goes down."
It would seem to be easier to explain these symptoms, if we looked at depression as an autoimmune disease of the brain. the immune system attacking various parts of the brain could cause all these symptoms. but how does a chemical imbalance in the brain cause all of these symptoms of depression?
Not all depression is caused by an imbalanced. We are hearing of depression more these days as a "chemical imbalance" because there are more drug companies out there producing their product to raise sales. Depression is simply a real problem , not necessary an imbalance all the time.
Many many diseases present with a variety of symptoms. Look at multiple sclerosis, or strokes, or even heart disease. A dozen people with any of these conditions may each present differently.
Human beings are complex individuals.
With mental/emotional diseases, there is the extra layer of that person's subjective life experiences thrown into the mix. the mind and the body are interconnected, so physical complaints may accompany the mental/emotional ones. (Think how you can feel emotionally lousy when you have a cold).
That is what makes medicine a challenging profession. if everyone acted the same, a computer could do the job.
depression is caused by a persons thought process.
chemical imbalance pure and simple. if there aren't neural transmitters there than the whole thing breaks down. the brain isn't fully explained just yet. new discoveries are made all the time
I don't know exactly how, but I think humans have evolved to have a whole body reaction to depression or anxiety.
I think this reaction was supposed to help you cope with whatever situation led to the depression or anxiety, but it doesn't seem to do the trick anymore.
What is interesting to me is that there is an entire range of reactions when it comes to appetite and sleep.