What causes depression?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

A variety of factors are known to contribute to depression, but researchers are still unsure of the specific cause. Heredity, childhood trauma, hormones, injury to the brain, drug abuse, and difficult life events have all been found to contribute to depression. The levels of certain neurotransmitters in your brain, particularly serotonin and dopamine, have also been linked to depression. A single one of these factors can cause depression, or a combination of many. It may also seem to have no cause whatsoever.

Loss of a loved one, stress and hormonal changes, or traumatic events may trigger depression at any age. Young children and teens can get depression but it can occur at other ages also. Depression is more common in women than in men, but men do get depression too.

This answer is based on source information from the National Institute of Mental Health.

Dr. Charles J. Sophy, MD
Adolescent Medicine Specialist


Depression is a disorder that occurs when the brain is not producing sufficient seratonin and other chemicals that promote positive moods. It can happen for no apparent reason, but sometimes has a catalyst event that triggers the condition. It is far worse than feeling "sad" or "down," as everyone feels from time to time. It is a genuine medical condition that goes far beyond the reaches of simple sadness.

Causes of depression are multifactorial; a combination of genetics and the environment. Genetics may place an individual at an increased risk to develop depression, although this likely will not cause depression without other factors coming into play.

Research suggests that depression is caused by a combination of genetic, biological, environmental and psychological factors. Depression is one of the most common mental disorders in the U.S.

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Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

There is no single cause of depression. In most cases, this disorder stems from a combination of genetic, environmental, and psychological factors. A person does not have to experience a traumatic or sad event in order to become depressed. What we do know is that the brains of people who are depressed tend to look different from the brains of people who are not depressed. Depressed people tend to show changes in the parts of the brain that regulate mood, behavior, sleep, and appetite. Furthermore, depressed people tend to have an imbalance in neurotransmitters—the chemical messengers of the brain. Serotonin is a neurotransmitter that regulates mood and other bodily functions. Diminished serotonin levels may contribute to depression. Many antidepression medications are targeted at serotonin to prevent its clearance or breakdown.




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Sometimes depression is stress-induced and caused by a clear trigger. It may be a painful divorce, a death in the family, or, for military personnel, time in combat. If the stressor is reduced or removed, depression may or may not be lifted. According to Alan J. Gelenberg, MD, professor and chair of psychiatry at Penn State's Milton S. Hershey Medical Center, physical illness can cause depression. Most doctors will do a physical exam. If your doctor thinks a thyroid problem, substance abuse, or other health condition is the cause of your depression, lab tests may be in order. Some medications can also cause symptoms of depression.

Research suggests that depression may result from four factors: biochemical, genetic, environmental and psychological.

Scientists have not discovered a "depression gene" but they have seen evidence, based on family histories, that suggests there may be a genetic link. Children of parents with major depression have a greater chance of experiencing depression than the general population. But depression also occurs in individuals in families without a history of the illness, so researchers continue to study additional factors.

People with depression have abnormal levels of brain chemicals called neurotransmitters, the messengers between the brain and the body.

People with certain characteristics such as low self-esteem and pessimism also tend to be more prone to develop depression. These characteristics, combined with stressors such as illness, relationships, major life events and financial problems can contribute to patterns of depressive illness. The onset of depression frequently is a combination of these causes.

There are many causes for depression, each reflecting different influences, yet most of these causes fall into two categories: organic or situational. Organic factors typically reflect biological vulnerabilities, such as family history of depression, while situational factors are most associated with life events, such as loss of a loved one due to death or divorce.

Depression can be hereditary and hormone shifts and changes can definitely trigger it or worsen it. There are many medications available to help you. You may want to ask your doctor about a birth control pill, as sometimes that can help even out hormonal fluctuations. There are many antidepressants that can help stabilize your mood. Getting exercise is great stress reliever and can help with depression as well. Lastly, you may want to try talk therapy—a therapist, either a social worker or psychiatrist, may be able to provide you with techniques to help you manage your feelings of frustration and mood swings. Your doctors can work with you to choose the best treatment for you and perhaps they can recommend some therapists in your area.

Dr. Michael T. Murray, ND
Naturopathic Medicine Specialist

Depression can be the result of psychological or physiological factors. The most significant psychological theory is the "learned helplessness" model, which theorizes that depression is the result of habitual feelings of pessimism and hopelessness. The chief physiological theory is the "monoamine hypothesis," which stresses imbalances of monoamine neurotransmitters, such as serotonin, epinephrine, and norepinephrine. Serotonin deficiency is the most common biochemical cause.

It is important to rule out simple organic factors that are known to contribute to depression, such as nutrient deficiency; drug use, including of many prescription and illicit drugs; consumption of alcohol, caffeine, and nicotine; hypoglycemia; hypothyroidism; and food allergy.

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Dr. Robert J. Hedaya, MD
Psychiatrist (Therapist)

Depression is caused by many factors, from the psychological, social, and environmental to the genetic, and metabolic. While it seems all depression are the same, perhaps caused by a serotonin deficiency, and require treatment with medication; in fact, depression is not ONE illness. It is very important to know the causes of depression and get proper treatment.

Genetics: There is growing evidence that there may be certain genetic vulnerabilities for depression.

Psychology and social factors: Helplessness, particularly around core issues (the need to be loved, to be loving, to have a sense of power, success, or control) reduces one’s self esteem.

Nutrition: Deficiencies, due to poor diet, poor digestion, absorption, or increased need for vitamins and minerals. Fat soluble vitamins (Vitamin D, Coenzyme Q 10) can cause or contribute to depression and have been shown to prevent antidepressant response.

Digestive disorders: Celiac disease and irritable bowel are associated with depression, quite possibly because they reduce availability of nutrients. Bacterial overgrowth of the small intestine can, as an example, reduce absorption of B12, leading to depression.

Immune system: Infection or inflammatory condition can precipitate, cause, worsen, or prevent response to standard treatment for depression.

Drugs and detoxification: Numerous drugs can cause depression, including a variety of medications for heart disease, antacids, antibiotics, anti-seizure medications, benzodiazepines, pain medications, hormones, asthma medications, over-the-counter medications.

Mitochondrial dysfunction: Can lead to marked reductions in energy, resulting in what appears to be depression.

Hormonal problems: Any hormonal system, when not functioning properly, can cause a mood disorder.

Tumors: Brain tumors often present with a psychiatric manifestation such as depression.

Sleep disorders: sleep apnea, nocturnal myoclonus, restless legs, decreased REM latency are all associated with depression.

Cardiovascular disease: reductions in cardiovascular function, oxygenation of the brain, exercise capacity, blood flow to the brain are all associated with depression, and can contribute to or cause depression.

Miscellaneous: anemia, B12 deficiency, bleeding, severe lung disease leading to decreased oxygenation of the brain, obesity, Wilson’s disease, and electrolyte abnormalities.

Decades of strict research have confirmed that depression results from a chemical imbalance in the brain. Often, this imbalance can be treated and rectified. It has nothing to do with character weakness or inability to cope.

The brain's chemicals become imbalanced for a number of reasons. Some individuals are genetically predisposed to depressive illness. Just as a diabetic's body does not make enough insulin, the bodies and brains of some depressed people do not create an ideal balance of neurotransmitters. In many cases, serious illness such as heart disease, diabetes or cancer sends some into depression. Beyond the fear and stress these diseases can cause, the very medications that treat them can initiate, mimic or intensify depression.

Events can send individuals into depression as well. When someone loses a loved one, of course mood will plummet. If the brain cannot revive from this lower mood on its own, medication and/or therapy often does the trick, returning the neurotransmitters to optimal levels. After a significant period, the individual can withdraw from the medication to monitor whether the better mood can be sustained. Many people need only be on antidepressant medication for a year or less.
Dr. John Preston, PsyD
Psychology Specialist
Depression can be caused by many factors. Most of the time, it’s a reaction to stressful life experiences, such as the loss of a loved one to death or divorce, the loss of a job, ongoing and severe familial stresses, and so forth. In addition to normal life stresses, certain biological changes can also trigger depression. These include a number of physical diseases. Some medical conditions change body chemistry and ultimately affect the delicate chemical balance of the brain. For this reason, it is strongly recommended that you see your physician and have a complete physical exam and basic lab tests to determine whether there are any medical conditions present that may be causing your depression.
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Researchers don't know exactly what causes depression, and there may be many factors. It may be related to hormones or to an imbalance of certain chemicals in the brain or to low levels of folate. Some people may have a genetic predisposition to depression or other aspects of their medical history that put them at risk. Sometimes you have to look beyond the obvious to search for and identify what is causing your depression. Once you find it, you may be closer to knowing how to treat it. Here are some possible causes:
  • Summer weather. If you thought seasonal affective disorder (SAD) only struck in the wintertime, you're wrong. It can also happen in the summer. There can be many reasons: a disruption in your normal routine, increasing heat and humidity, or body image issues.
  • Internet addiction. British researchers found that "Internet addicts" had a higher incidence of moderate to severe depression.
  • Underactive thyroid. Having a thyroid that is underactive, or sluggish, has been linked to depression. In hypothyroidism, which affects almost 10 million Americans, the thyroid not does produce enough thyroid-stimulating hormone, which can create a wide range of symptoms, including depression, mood impairment or trouble with concentration. Blood tests to measure your thyroid function can confirm this condition, which is treatable with medication.
  • Urban dwelling. Where you live can affect your mood due to higher levels of stress in urban areas.
  • Inadequate sleep. There's a powerful link between sleep and depression, and it works both ways. Depressed people may have more trouble sleeping, but lack of adequate sleep can also lead to depression. Being exhausted can make you feel tense and irritable and be much less likely to get proper exercise, which can also prevent you from feeling your best. Regular exercise has been proven to reduce stress and help alleviate feelings of anxiety and depression.
If you think you may have depression, talk to your healthcare provider immediately. Don't wait another day.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.