Causes Of Depression
– A Comprehensive Summary
The search for the causes of depression does not yield a simple answer.
This is not surprising. There are many factors – genetic, environmental, social/psychological, medical and lifestyle factors – that can bring about this complex illness with its characteristic array of physical, psychological and emotional symptoms.
In fact, studies suggest that depression is usually caused by a combination of many of these factors, rather than by a single factor. The combination of factors can then differ widely from one depressive to another.
Below, we explore some of the causes of depression, some of which are more commonly known than others.
Causes of depression: Neurotransmitter Imbalance
One of the most widely accepted explanation for causes of depression is imbalances in neurotransmitters (bodily chemicals responsible for the transmission of signals between nerve cells).
The neurotransmitter imbalance that most people associate with depression is deficiency in serotonin. Serotonin is a neurotransmitter that plays a major role in countering the brain’s stress response and reducing anxiety .
Besides serotonin imbalances, norephinephrine and dopamine imbalances are also found to be linked to depression. In turn, the monoamine hypothesis suggests that deficiency in these 3 monoamine neurotransmitters causes depression .
In fact, many pharmaceutical drugs for depression are based on the monoamine hypothesis and they work by altering the metabolism and levels of these neurotransmitters in the brain. Some of the causes of depression that are discussed below (e.g. genetic disposition) are also linked to imbalances in neurotransmitter levels.
Another neurotransmitter, which imbalance can create havoc to your emotions and mental well-being, but is less well-known, is histamine. Too little histamine can bring about suspicion or paranoia, while too much histamine can leave one so exhausted from over-stimulation that he or she ends up in a depressed state. 
Find out how you can re-balance your histamine levels to overcome your histamine-linked depression.
Causes of depression: Genetic disposition
Evidences  that suggest the role of genes in depression include:
- Identical twins (with identical genes) being more similar in their susceptibility to depression than fraternal twins.
- Biological children of depressed parents being more susceptible to depression than adopted children.
A particular gene that has been found to be linked to depression is the serotonin transporter gene. This gene affects the function of serotonin in the body. In turn, two versions of the gene’s promoter region (a region of DNA that initiates transcription of the gene) are found to exist – one version is longer and the other is shorter. 
The shorter version is found to result in less effective serotonin functions, as well as a greater disposition for anxiety and the runaway stress response. In turn, a recent large scale study on New Zealanders found that young adults with the shorter version are about 2.5 times more likely than those with the longer version to become depressed when faced with severe negative life events. 
Nonetheless, according to Stephen S Ilardi, Ph.D., associate professor of clinical psychology at the University of Kansas, studies show that genes probably account for only about 40% of the risk for depression . In other words, our environment – i.e. all the things we experience – also has a major role to play.
Causes of depression: Environmental factors
Lack of sunlight
The lack of exposure to sunlight is one of the causes of depression. The lack of sunlight can disrupt important circadian rhythms in the body, and subsequently trigger depression. 
Decreased sunlight exposure can occur during the dark days of the winter season, and contribute to what is known as the Seasonal Affective Disorder (SAD), or the Alaska Effect.
Besides weather and climatic conditions, the modern lifestyle can also contribute to decreased sunlight exposure.
The modern lifestyle is characterized by spending many hours indoor, whether in the office (for work), in the shopping centres (for play) or at home. And since natural sunlight (even on a cloudy day) is very much brighter than indoor lighting, the modern man who is indoor from dawn to dusk often finds himself a victim of sunlight deficiency problems, including light-related depression. 
Heavy metal and mineral toxicity
Pollutants in your environment (including your drinking water and food) could expose you to levels of minerals and heavy metals beyond what is good for your well-being.
While some minerals (e.g. copper) are necessary for bodily functions, they are actually toxic in large amounts. And when it comes to heavy metals (e.g. lead, mercury, cadmium), they are toxic to the body even in minute quantities. 
Indeed, it has been found that a buildup of heavy metals and minerals such as cadmium, lead, copper and mercury can bring about severe brain changes, including depression, paranoia and hallucinations and more. 
Find out more about how heavy metal and mineral toxicity contributes to depression, as well as how you can overcome your depression by eliminating the toxicity in your body.
Causes of depression: Psycho-social factors
Prolonged periods of stress as a result of our modern lifestyles (e.g. work stress, rush hour, etc) or unresolved emotional issues can increase our vulnerability for depression.
However, the onset of depression is usually triggered by the added stress of more painful or traumatic, high-impact life event(s)  like accidents, natural disasters or violence (e.g. abuse), divorce, loss of job, loss of loved one, illness, failure or rejection, financial setbacks, geographical relocation etc.
Severe childhood trauma such as physical or sexual abuse also increases the risk of depression later in life (i.e. as adults). According to Dr Ilardi, it is as if the early traumatic event(s) had left an enduring imprint on the brain, such that the stress response systems in these individuals are on permanent alert mode, and are difficult to switch off once activated into a state of overdrive. 
Find out about when and how stress leads to depression. Find out about the Emotional Freedom Technique to deal with your emotional issues. Also, learn how to relieve your stress using relaxation techniques (including meditation), exercise and other methods.
Nonetheless, traumatic or stressful life event(s) alone cannot predict the onset of depression. The way we think or react to potentially stressful events can sometimes be more important in shaping our feelings than the events themselves.
That is why people with negative thought patterns, or the unhealthy tendency to brood over negative event(s) and thought(s), ie. ruminate, are often at higher risk of getting depression when encountered with traumatic or stressful life event(s), as compared to those with positive thought patterns. 
Learn how to deal with your rumination habits using 2 main steps – increasing your self-awareness, and learning to redirect your attention. Also, overcome your negative thinking patterns using cognitive therapy.
Lack of social support
Studies show that people with strong social support networks are less likely to become depressed as compared to those without. 
It seems that the supportive presence of loved ones is a powerful signal from the environment that helps to moderate the brain’s stress response. Even having a pet seem to provide some protection (in the absence of a supportive other person), through the comfort of having close physical contact with another living thing. 
On the contrary, negative relationships (eg. harshly critical, emotionally abusive ones) can render a person more vulnerable to depression than if he or she had no supportive relationships at all. 
Causes of depression: Lifestyle factors
Use of substances
Those whose lifestyles include the use of substances (including recreational drugs, prescription medication, nicotine, alcohol and caffeine) may be at higher risk of depression as compared to those who do not use substances.
Nicotine in cigarettes has been found to increase the release of cortisol, which in turn reduces the level of serotonin and melatonin in the body. Cigarette smoke also uses up vitamin C in the body. All these factors contribute to increased risk of depression in cigarette smokers. 
Like nicotine, alcohol consumption also increases the risk of depression. Alcohol increases the release of adrenal hormones, which in turn affect serotonin levels in the brain. Alcohol also disrupts normal sleep cycles as well as contributes to hypoglycemia, both of which are causes of depression. 
Links have also been found between caffeine consumption and depression. Studies found that depressed patients tend to have high (more than 700mg daily) caffeine consumption habits. In fact, it was found that the higher the caffeine intake, the more severe the depression. And the combination of caffeine and refined sugar appears to do more harm than either substance consumed alone. 
Drugs like some common antibiotics, anti-inflammatory drugs, antihistamine, blood-pressure drugs, corticosteroids, glaucoma drops, hormones and medications to lower cholesterol can also trigger depression [5, 6]. Nasal decongestants containing phenylpropanolamine has also been known to induce psychiatric crises in those with depression or other mood disorders .
Yet many physicians fail to warn their patients about the depressive side effect of these drugs when prescribing them. 
Substances like amphetamines, cocaine, barbiturates and marijuana can worsen depression. .
Similarly, some pharmaceutical antidepressants have been found to worsen depression and increase the risk of suicide 
Lack of physical exercise
Dr Ilardi  believes that the active lifestyle of our hunter-gatherers ancestors confer them protective factors when it came to depression. On the contrary, the modern sedentary lifestyle we have today provides no protection against depression.
In fact, studies found that the effects of aerobic exercise were comparable to that of antidepressant medication, without the side effects and with the additional benefit of reducing relapse .
Causes of depression: Pre-existing medical conditions
Many of the depression causes mentioned in this section support the view that depression is a physical condition that expresses itself in emotional symptoms .
As discussed above, imbalances in neurotransmitters such as serotonin, norephinephrine, dopamine and histamine are causes of depression.
Hormonal imbalances have been found to be one of the causes of depression.
It is probably well accepted that women are more prone to depression than men. However, as observed by Dr Ilardi, this difference is only during the prime reproductive years, when sex hormone levels are at their highest. In fact, women are highly vulnerable to depression during the premenstrual period, right after childbirth and in the years leading up to menopause, when the levels of sex hormones (e.g. estrogen, progesterone and testosterone) in the body are rapidly changing. .
Such a situation serve as evidence that it is the sex hormones, rather than gender per se, that have large effect on mood and other depressive symptoms.
Besides the sex hormones, having a deficiency in thyroid hormones (otherwise known as hypothyroidism) can also cause depression. In fact, depression is often an early sign of the thyroid disease [4, 9].
Nutritional deficiencies or poor dietary habits
Unknown to many, inadequate nutrition (or nutritional deficiencies) can contribute to depression, because your body does not receive the essential nutrients (e.g. vitamins and minerals, essential fatty acids, essential amino acids) it needs to maintain good physical and mental/emotional well-being.
Poor dietary habits (e.g. high intake of refined sugars, alcohol, caffeine) can also limit your body’s access to the important nutrients that your body needs, and as such contribute to the development of depression.
Besides nutritional deficiencies and poor dietary habits, diets for lowering cholesterol have also been found to increase the risk of depression. Such diets usually focus on limiting total fat intake while increasing the intake of polysaturated fats (e.g. corn, soybean oil), and as such can upset the balance of Omega 3 to Omega 6 ratio essential for ensuring physical and mental well-being. 
Food additives like the artificial sweetener, Aspartame (e.g. NutraSweet, Equal) can block the formation of serotonin and worsen depression in those who are already serotonin-derived .
Read more about dealing with your depression the nutritional way – by ensuring sufficient amino acids (e.g. Tryptophan, Tyrosine and L-Phenylalanine, SAM e, and other amino acids), Omega 3 fatty acids, vitamins (e.g. B vitamins, vitamin D) and minerals.
It is widely recognized in the field of alternative medicine that food allergies are a potential cause of mental disorders, especially depression. Indeed, the American College of Allergy and Immunology notes that food allergy can trigger the following conditions besides depression – chronic fatigue syndrome, attention deficit, headaches, hyperactivity, insomnia and sleep disorders, learning disorders . In turn, the foods you are addicted to and choose to binge on can give you a clue as to what you might be allergic to.
Find out more about treating your food allergies to overcome your depression naturally.
Candida, or candida albicans, is a strain of yeast that is found normally in the digestive tract and skin of almost every healthy person. In healthy individuals with strong immune systems, the yeast is harmless.
However, when the balance of the intestinal environment is upset, the candida yeast proliferates. Among the various clinical manifestations of candidiasis, fatigue and depression are two of the main symptoms experienced by many candidiasis sufferers.
Find out how you can overcome your candida-linked depression using the anti-candida diet.
Since the brain requires a constant supply of blood sugar to function properly, it is no surprise that excessively low levels of blood sugar (i.e. hypoglycemia) can lead to depression. In fact, studies have shown that hypoglycemia is very common among individuals with depression .
Because of the modern day diet that is high in refined sugars and starch, hypoglycemia is a common ailment these days. Nonetheless, as many conventional doctors do not acknowledge the existence of this condition, many hypoglycemia sufferers often go undiagnosed, and their hypoglycemia-linked problems are left unaddressed.
Find out more about how you can overcome hypoglycemia-linked depression using the euglycemic diet.
Poor sleep is both a symptom of depression as well as one of the causes of depression.
Research on animals and humans has shown how deprivation of slow-wave sleep can lead to brains malfunctioning, bodies becoming seriously ill, moods turning down, thoughts becoming negative and social interest disappearing. 
Other medical conditions
Besides hypothyroidism, there are other medical conditions that can also give rise to depression.
Such medical conditions  that can cause depression include:
- a coagulated blood mass in the brain (due to stroke or physical head injury),
- mal-absorption due to various gastrointestinal conditions (leading to nutritional deficiencies),
- Cushing’s syndrome (due to the presence of a steroid-producing tumor),
- lupus erythematosis (an autoimmune disease affecting mostly young women and characterized by a butterfly-shaped rash across the nose and checks),
- tumor of the pancreas,
- Wilson’s disease (a genetic condition where copper accumulates in the brain and other organs),
- normal pressure hydrocephalus (abnormal accumulation of fluid in the brain leading to an increase in the skull),
- pheochromocytoma (tumor that floods the body with adrenaline),
- Addison’s disease (failing of the adrenal glands often accompanied by spontaneous tanning),
- hyperparathyroidism (endocrine disorder).
This list is not exhaustive.
Getting treatment for your depression
Given the complexity of the causes of depression, if you suspect that you are clinically depressed, first see a doctor to rule out any underlying medical illness, before you consult a psychologist or psychiatrist for a diagnosis and appropriate treatment.
Be mentally prepared that some conventional therapists may be unaware of some of the above factors and their links to depression. As such, we hope that the list of causes of depression above can provide you with some leads as to identifying the causes of depression for you.
If you wish to deal with your depression naturally, it would be best to work with a doctor/psychiatrist who embraces natural therapies for depression and will work with you to address the root cause of your depression problem.
Also, check out the various natural remedies that you can adopt for dealing with your depression. If you are unsure about where to start, begin with the Holistic-Depression-Help step-by-step guide to overcoming your depression naturally.
 Ilardi, Stephen S., PhD. The Depression Cure: The 6-Step Program to Beat Depression Without Drugs. Cambridge, MA: Da Capo Press, 2009. Print.
 “Major Depressive Disorder”, extracted from http://en.wikipedia.org/wiki/Major_depressive_disorder, on 5 Aug 2013
 Larson, Joan Mathews, PhD. Depression-Free, Naturally: 7 Weeks to Eliminating Anxiety, Despair, Fatigue, and Anger from Your Life. NY, USA: Ballantine Books, 1999. Print.
 Murray, Michael, ND, and Pizzorno, Joseph, ND. Encyclopedia of Natural Medicine. 2nd ed. New York, NY: Three Rivers Press, 1998. Print.
 Balch, Phyllis A., CNC. Prescription for Herbal Healing: An Easy-to-Use A-to-Z Reference to Hundreds of Common Disorders and Their Herbal Remedies. New York, NY: Avery, 2002. Print.
 Balch, James F., MD, and Stengler, Mark, ND. Prescription for Natural Cures: A Self-Care Guide for Treating Health Problems with Natural Remedies Including Diet and Nutrition, Nutritional Supplements, Bodywork, and More. Hoboken, New Jersey: John Wiley & Sons, Inc, 2004. Print.
 Balch, James F., MD, Stengler, Mark, ND, and Balch, Robin Young, ND. Prescription for Drug Alternatives: All-Natural Options for Better Health without the Side Effects. Hoboken, New Jersey: John Wiley & Sons, Inc, 2008. Print.
 Gaby, Alan R., MD. The Natural Pharmacy: Complete A-Z Reference to Natural Treatments for Common Health Conditions. 3rd ed. New York, NY: Three Rivers Press, 2006. Print.
 Baumel, Syd. Dealing With Depression Naturally. New York, NY: McGraw-Hill, 2000. Print.