By Walter Sorochan Doctor of Health Á Safety; Emeritus Professor San Diego State University
Posted February 10, 2019; Updated October 2021. Disclaimer The information presented here is for informative and educational purposes only and is not intended as curative or prescriptive advice.
Everyone gets depressed at one time or another. This is the 'mind' canary in the human body telling us how we feel. We feel good when we are successful and sad when we fail. Feeling depressed is your body telling you that something is wrong with your body and/or lifestyle! Depression is a symptom more so than a disorder or disease. This article helps you get acquainted with the possible causes of depression and how to prevent it.
Depression is referred to as feeling sad, lonely and is often accompanied by a sense of hopelessness, fatigue, lack of interest, low self-esteem and in some cases, thoughts of suicide. It is normal, at one time or anther, to felt 'blue' for a day or two when having a bad day or experience. But it is being sad and lonely for a long time, or chronic depression, that becomes unhealthy. 
Chronic depression is different from normal sadness — like when you lose a loved one, experience a relationship breakup, or get laid off from work — as it usually consumes a person in their day-to-day living. It doesn’t stop after just a day or two — it can continue for weeks on end, interfering with the person’s work or school, their relationships with others, and their ability to just enjoy life and have fun. As one can surmise from this short view of depression, it indeed is difficult to judge when a depression is a normal part of the ups and downs of daily life, a disorder; and especially if we do not know what caused it in the first place.
Most recently, the numerous depression-suicides of professional football players have ignited attention about depression in general   and mental illness And concussions have alerted all of us that American football players, as well as all body contact sports, including boxing, soccer, and basketball, are prone to concussion and brain damage. But depression is not just a football or sport issue. War veterans, suffering from battlefield mine explosions, experienced brain damage and depression similar to those of football players.
Additional reports indicate that depression among the general population is linked to a major depressive disorder, or chronic depression, and that depression is characterized by a combination of symptoms that interfere with a person's ability to work, sleep, study, eat, and enjoy once-pleasurable activities. 
While football player brain concussion is linked to later retirement depression, explaining what happens to the brain in concussion over time is somewhat controversial at this time. Although biological, psychological and environmental theories have been advanced, the underlying patho-physiology of depression remains unknown and it is probable that several different mechanisms are involved.   One thing for sure, the autopsy brains of those suffering from chronic depression undergo change.
Causes of Depression
Although there is no agreement among medical researchers as to what causes depression in most persons, this author proposes six basic causes:
The medical profession seems to overlook these as primary causes of depression.
There is strong research that lack of adequate exposure to sunshine causes depression! It is sunshine that stimulates the skin to synthesize hormone D, that in turn, helps to prevent depression.  The real problem of depression, being linked to hormone D, is really a lifestyle that lacks of exposure to sunlight.It is lifestyle related.
One aspect of lifestyle that most of us cannot control is where we live. Where you live affects the amount of sunshine you can get.
Who is susceptible to depression linked hormone D deficiency?:
Skeptics may argue that sunshine exposure is dangerous because it can cause cancer. Or that over-exposure to hormone D can be dangerous. But both are scare tactics and not true!
Safe exposure to sunshine: Dosage or the safe amount varies with different ages and bio-chemistry of people.  "There has never been a report of any reader deaths from medical school-induced hypervitaminosis."  body stops making hormone D when the dosage amount per day reaches 10,000IU [ 250 μg ]. Mega-doses of 50,000 IU and more IU per week or month have been medically administered with no ill effects. Hormone D is safe; but you should be under the guidance of a medical doctor when taking mega-doses. With long exposure to UVB rays, an equilibrium is achieved in the skin, and excess vitamin D simply degrades as fast as it is generated. So you need exposure to sunshine hormone D every day.
Government recommended dietary intakes [RDI] of 200 to 600 IU/day are too low, according to clinical evidence. Government "tolerable" or "safe upper intake levels" (UL) of 1,000 to 2,000 IU/day are likewise also too low, and largely unsupported by toxicological evidence. An optimum health recommendation is minimal 4,000 to 5000 IU/day.
ALERT: When is it enough sunshine? Although the body may no longer make raw pre-hormone vitamin D from UVB, the body can get sunburned from excess UVA radiation. Body sensors monitor exposure to sunlight and send warning signals: after 15 to 20 minutes of sun exposure, your light colored skin may start to itch and start turning a pink or reddish color; letting you know that you need to stop "frying your skin." It is continuous over-exposure of your skin many times over many years to UltraViolet A [not UVB] rays that causes extreme sunburn damages to the skin and can eventuate in skin cancer. This can be avoided! Prevent getting sunburn: Get out of the sun after half an hour, or put sun-cream on exposed parts of body and wear clothing.
Vitamin D test: To determine whether you need to supplement with vitamin D, you should test your vitamin D level by doing the 25-hydroxy D lab test, which measures 25(OH)D. Ask your medical doctor for this test.
Researchers have found that persons deficiencnt in magnesium [Mg]were predisposed to depression. Majority of persons in United States are deficient in magnesium. Taking Mg supplements without companion helper vitamins and minerals may not help the body to utilize magnesium well.
However, there is a study that people can benefit from MG supplements. In one study, patients with schizophrenia were studied for magnesium benefits. "Schizophrenic patients were found to have low erythrocyte magnesium levels." Inadequate magnesium levels can contribute to insomnia, seizures, anxiety, pain, and other neuropsychiatric problems.  Eby and Eby have found that depressed persons treated with adequate doses of magnesium recover rapidly in about five days.  Dietary sources high in magnesium include dark-green leafy lettuce, spinach, sunflower seeds, almonds, peanuts, and sesame seeds.
Having supporting friends and family is a survival need. It is this survival need that helps prevent falling into a chronic depression. Friends can fill that vacuum of loneliness and defuse the sense of feeling sad and alone. One needs to build a support social network to brighten the blue days. This should be common sense but many lack such an understanding and how to build the social circle of friends.
Preventing depression with lifestyle changes! What you can do?
1. Get more exposure to sunshine throughout the year. You need, depending on your age and skin color, about 15 to 30 minutes of sunshine exposure each day on about 30 or more percent of your body. Sunshine releases serotonin .... the feeling good hormone. This is the best way to get adequate amount of sunshine that activates hormone D synthesize in your body.
Dark skinned persons need more sun exposure than light skinned persons. As we get older [especially after age 60] the skin gets thinner and loses much of its ability to absorb ultraviolet B that stimulates fat cells in the skin to synthesize hormone D. This explains why the elderly are more prone to vitamin deficiency.
2.Hormone D supplementation: Get the right kind --- vitamin D-3. Avoid D-2. If you go to your doctor, there’s about a 75 percent chance he is going to prescribe you an antidepressant drug. And there could be an almost a 90 percent chance you don’t need it. 
3. Foods: Most foods do not have hormone D. Ocean plants like spirulina and chlorella have good amounts of vitamin D while ocean salmon and sardines have very little vitamin D. Fish cannot synthesize vitamin D. Fish get theirs early in the food chain from planktonic algae, little fish eat plankton plants and big fish eat little fish, and if we eat them, we get a very small amount of vitamin D-2. -
Many therapists have recognized diet playing a significant role in brain health. Foods high in refined sugars and carbohydrates contribute to depressive symptoms while organic fruits and vegetables alleviate them.
4. Get exercise in the sun: Physical exertion increases circulation to your brain, giving you fresh blood and oxygen, reinvigorating your mood. Exertion also releases serotonin – the “feel good hormone” – in your brain. Exercise and going outdoors are two of the best ways to avoid becoming depressed. The feel-good effect is multiplied if you can exercise outside.
5. Get adequate amount of magnesium.
6. Take supplement vitamin B6 [Pyridoxine]: Many people who are depressed are deficient in vitamin B6 and probably B-complex vitamins. And the more vitamin B6 and B-complex vitamins you have, the less likely you are to be depressed. Especially for men. B6 is vital to regulation of mental function and mood. Two of the best food sources are chickpeas and chestnuts. Other foods rich in B6 include bananas, tuna, turkey, eggs and spinach. 
7. Co-factors help hormone D work: How well hormone D works depends on the amount of other vitamins and minerals that are present in your body. You need to ingest other vitamins, minerals and amino acids, as helpers, in your total diet in order to help hormone D work. e.g. magnesium, calcium, phosphorus, B-complex vitamins, organic sulfur, zinc, boron, vitamin C, vitamin A. So ingesting vitamin-mineral supplements by themselves will not keep one optimally well when helper nutrient are ignored.
8. Depression linked to colon bacteria: Lower levels of hormone D [sunshine] changes the bacteria in our intestine. This results in fewer good colon bacteria to synthesize the 8 B-Complex vitamins; in turn, making one more susceptible to depression.
What one eats has been linked to colon bacteria and in turn, the degree of depression. A new Belgian research reveals a link between specific types of gut bacteria and depression.  The findings, published in the journal Nature Microbiology, compared fecal microbiome data with general practitioner diagnoses of depression from 1,054 individuals. Researchers studied the genomes of more than 500 bacteria isolated from the human gastrointestinal tract and identified two bacterial genera, Coprococcus and Dialister, that were consistently depleted in people with depression, regardless of antidepressant treatment. Unfortunately, the study is flawed as the researchers did not account for two well known factors causing depression .... foods eaten and the degree of exposure to sunshine to account for hormone D [vitamin D].
9.Socialize - Friends are your warm blanket against depression. Join a dance club, a sports club or other support organization where you can make friends. Surround yourself with those who have a positive outlook on life as they can infect you with their outlook. Get 10 hugs a day!
10. Find something to do that gives your life meaning and purpose. Depressed persons often feel empty inside and need to give meaning to their life. It should be more than just raising a family or having a job or watching TV. It could be doing philathropic work where you can feel good about yourself and also meet others.
You can minimize and avoid depression by changing your lifestyle! Free sunshine may be your best medicine.
Anti-depressant medications prescribed by doctors do not work. There is new evidence that such medications may cause Alzheimer's disease.
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