Depression is a symptom. With an out of balance chemistry you get physical discomfort as well as mental phenomena. Irritability, anger issues, fits of being "touchy" all the time. Depression is an end result. You don't just get depressed, you end up depressed. It starts with tension, and pressure, and builds to stress and anxiety, as treatment after treatment, and doctor after doctor fail to find solutions, or even what is wrong with you it builds and builds and you end up breaking down, and breaking down emotionally, further and further, until you are in a state of deeeeeeep depression.
It is AWEFUL!!! I know I have been there many times.
I have Grave's Disease, and had a bad bout of Candida, and Leaky Gut Syndrome, and even getting the biology under control, I still had emotional problems. It is from constantly battling circumstance, and the main circumstance of just not feeling well all the time. That is stressful. With or with out the chemistry problems. Cortisol is a stress compound. My Cortisol test was off the chart and all over the place at different times of the day, and was in the WRONG places at those times. When it should be high it was low, and vice versa.
There is a connection between emotions and the body, but emotions are NOT CHEMICAL!!!!! They are an ENERGY!!!! The connection is the nervous system. The Nervous System CONDUCTS ENERGY!!!! Like wires conduct electricity!!!!! You have a connection of NERVES through out your body. All sensations go through it to your brain. YOUR MIND, or what you call your mind, is what RECOGNIZES the situations, and environment you are in. Consciousness, awareness, etc... It is an Energy Array, of things coming together in a centralized location, The Brain. This give the illusion that "you are in your head". But you also FEEL things in other areas. "Joy in your Heart". "Fear in your gut". "Stress in your Stomach". "Depression from the head down". IT IS THE NERVOUS SYSTEM AND YOUR RECOGNITION OF CIRCUMSTANCE THAT SEND THESE MESSAGES OF ENERGY TO LOCATIONS!!!!!!!!!!
Emotions themselves are not Chemical. They are an energy. A wavelength like light. It emanates, and radiates like heat. Chemistry also is an ENERGY. Not just the chemical compounds!!!! You often get heat from a chemical reaction. Just put Soda in Vinegar in a pill bottle and try to hold the cap down!!!! That is a release of energy. Not just a chemical reaction. That is how we go into space.
The chemistry can be "out" for many reasons. Toxins, deficiency, etc. ORGANS FAILING!!!! GLANDS FAILING!!!! GLANDULAR OR ORGAN DAMAGE!!!!!! On going stressful situations. Even physical conditions you don't consider or recognize, can be stressful. My father went in for Radiation Therapy for a lump on his prostate. He has gotten over most of his stress, by DISCONNECTING HIMSELF. So he did not recognize the stress his body was going through at a CELLULAR LEVEL from the radiation. He ended up one day with a bacterial ulcer that had been waiting for stress to kick it in. I had to take him to the hospital. He lost two-thirds of his BLOOD from vomiting it up!!!! He did not tell me, he was having trouble that is why it went on so long. Before he was diagnosed with a lump. He was fine. He had no problem. He had disconnected himself so much from things. He just denied anything stressful. But it was STILL THERE... He was suppressing and repressing it. HE STILL DOES. Fortunately he lived through all that. He is 88 now.
Back to emotions and depression. Depression, as an end state, has BOTH emotionally not feeling well, and the out chemistry. BUT EVEN SO IS JUST ANOTHER SYMPTOM!!!! doctors will treat the SYMPTOM that they see!!!!!! They generally don't look much further or you need to see a specialist. You need to treat the cause. That is the underlying thing or circumstance that brought it about.
With no thyroid that is not an option for me. With Diabetes that has its own options.
With EMOTIONS that can be addressed DIRECTLY!!!!!! If depression, connected to Diabetes or any other circumstance is bothering you, there is help. There is a work called "Happiness Is No Charge". It describes a technique for getting rid or control over negative emotions. And can therefore take care of a significant piece of the puzzle. I have been doing the technique for 2 and a half years. I have used it on negative emotions, stress, pressure, anxiety, DEPRESSION, suppress, repression, oppression, irritation, frustration, etc....
I used it on a past anxiety attack, the incident now no longer bothers me!!!! I used it yesterday and the day before, when I had a dead battery, and the ensuing frustration. The technique helped GREATLY in keeping me under control and not "losing it". The stress started to build and I just did the technique and that kept it in check, and after the situation was over with, I did the technique until the negative emotions went AWAY!!!!!!!!!!
It is a simple, easy, 1,2,3, step technique, I think a 6 year old could do it. It is inexpensive and comes in two versions. Go here for more information.

www.feelbetter.co.nr

It works on past and present upsets. You are STILL CARRYING THE BAGGAGE FROM WHEN YOU WERE A CHILD!!!! This technique helps get people over TRAUMA!!!! ILLNESS IS A TRAUMATIC EXPERIENCE THAT IS WHY YOU REACT EMOTIONALLY AND THE BODY IS REACTING IN STRESS MODE!!!!!!!!!! The shock and the Trauma, the Pain and the Suffering of illness and disease. That circumstance that YOU recognize.
This technique gets at that DIRECTLY!!!!! SHOCK is another thing it gets at. So it gets at the causes and manifestations of PAIN AND SUFFERING!!!!!! Pretty good for JUST ONE, SIMPLE TECHNIQUE!!!!!!!!!!!!!
How can it do that? The mind is a simple, yet complex combination of PERCEPTIONS! And your SENSATIONS are recognized there. Your sensations of sight, sound, smell, taste, and touch are all brought to a central location, and YOU LOOK AT IT!!!!!!!! That is really ONE MECHANISM!!!! It is an ENERGY....IT IS CALLED "CHARGE" as in "Traumatic Charge". This technique DISSIPATES the "Traumatic CHARGE" of even years and year of bad experiences!!!!!!
And best yet. IT IS A PERSONAL THERAPY!!!! YOU DON'T NEED A PRACTITIONER!!!! I do the technique on myself. I don't even DO IT OUT LOUD!!!!! You can do the technique ANYWHERE!!!!!
Well worth your checking out. Very inexpensive!!!!!!
I have a friend. His daughter was type-2 and has just been diagnosed as Type-1. As far as I have read, it is a deficiency, and possibly toxin caused disease. Organs are attacked, and don't function. So detox and nutrition, exercise, etc... help get it under control. I have two other friends who have it. My Aunt went border-line diabetic at the end of her life at 82. Her endocrine system just started shutting down. SHE WAS A HEALTH NUT!!!!! Balanced diet, exercise, live in the mountains, etc... Very, Very, Very much a POSITIVE PERSON ALL HER LIFE!!!!!!
My great aunt, THE HATER, lived to be 90!!!!!!!! But she ate right, and worked in the garden.
So do the best you can in life.
Be well and happy. Because LIFE IS TOO SHORT to live ANY OTHER WAY!!!!!!!!!!

Steve

By the way. The Technique also works with psychosomatic things as they are from the MIND! It can work to SOME extent on physical things. I have had modest success with some things. I think some had a psychosomatic remnant from the bad experience. This is explained in the WORK.

Be well and happy.
Steve

When you said the researchers adjusted for outside factors including obesity, smoking, sedentary lifestyle and blood sugar levels, did you mean they adjusted for EACH of these factors separately, or ALL of them combined?
If the answer is ALL of them combined then there is no mystery.
Having worked in eye health for 35 years I see patients with diabetic retinopathy every day. Patients also suffering from depression do not deal with ANY of the above factors as well as those not suffering from depression. So the combined effect would be much poorer control of their diabetes and over an extended period progression of retinopathy.