Causes of Depression

Have you ever wondered what causes clinical depression? Perhaps you have been diagnosed with major depression, and that's made you question why some people get depressed while others don't.

Depression is an extremely complex disease. It occurs for a variety of reasons. Some people experience depression during a serious medical illness. Others may have depression with life changes such as a move or the death of a loved one. Still others have a family history of depression. Those who do may experience depression and feel overwhelmed with sadness and loneliness for no known reason.

What Are the Main Causes of Depression?

There are a number of factors that may increase the chance of depression, including the following:

• Abuse. Past physical, sexual, or emotional abuse can cause depression later in life.
• Certain medications. For example, some drugs used to treat high blood pressure, such as beta-blockers or reserpine, can increase your risk of depression.
• Conflict. Depression may result from personal conflicts or disputes with family members or friends.
• Death or a loss. Sadness or grief from the death or loss of a loved one, though natural, can also increase the risk of depression.
• Genetics. A family history of depression may increase the risk. It's thought that depression is passed genetically from one generation to the next. The exact way this happens, though, is not known.
• Major events. Even good events such as starting a new job, graduating, or getting married can lead to depression. So can moving, losing a job or income, getting divorced, or retiring.
• Other personal problems. Problems such as social isolation due to other mental illnesses or being cast out of a family or social group can lead to depression.
• Serious illnesses. Sometimes depression co-exists with a major illness or is a reaction to the illness.
• Substance abuse. Nearly 30% of people with substance abuse problems also have major or clinical depression.

How Is Biology Related to Depression?

Researchers have noted differences in the brains of people who are depressed as compared to people who are not. For instance, the hippocampus, a small part of the brain that is vital to the storage of memories, appears to be smaller in people with a history of depression than in those who've never been depressed. A smaller hippocampus has fewer serotonin receptors. Serotonin is a calming brain chemical known as a neurotransmitter that allows communication between nerves in the brain and the body. It's also thought that the neurotransmitter norepinephrine may be involved in depression.

Scientists do not know why the hippocampus is smaller in those with depression. Some researchers have found that the stress hormone cortisol is produced in excess in depressed people. These investigators believe that cortisol has a toxic or poisonous effect on the hippocampus. Some experts theorize that depressed people are simply born with a smaller hippocampus and are therefore inclined to suffer from depression.

One thing is certain -- depression is a complex illness with many contributing factors. The latest scans and studies of brain chemistry that show the effects of antidepressants help broaden our understanding of the biochemical processes involved in depression. As scientists gain a better understanding of the cause(s) of depression, health professionals will be able to make better "tailored" diagnoses and, in turn, prescribe more effective treatment plans.

How Is Genetics Linked to the Risk of Depression?

We know that depression seems to run in families. This suggests that there's a genetic link to depression. Children, siblings, and parents of people with severe depression are much more likely to suffer from depression than are members of the general population. Multiple genes interacting with one another in special ways probably contribute to the various types of depression that run in families. Yet despite all the evidence of a family link to depression, scientists still have not been able to identify a "depression" gene.

Can Certain Drugs Cause Depression

In certain people, drugs may lead to depression. For example, medications such as barbiturates, benzodiazepines, and beta-blockers have been associated with depression, especially in older people. Likewise, medications such as corticosteroids, opioids (codeine, morphine), and anticholinergics taken to relieve stomach cramping have been found to cause mania, which is a highly elated state associated with bipolar disorder. 

For in depth information, see WebMD's Medicines That Cause Depression.

What’s the Link Between Depression and Chronic Illness?

In some people, a chronic illness causes depression. A chronic illness is an illness that lasts for a very long time and usually cannot be cured completely. However, chronic illnesses can often be controlled through diet, exercise, lifestyle habits, and certain medications. Some examples of chronic illnesses that may cause depression are diabetes, heart disease, arthritis, kidney disease, HIV/AIDS, lupus, and multiple sclerosis (MS). Hypothyroidism may also lead to depressed feelings.

Researchers believe that treating the depression may also help the co-existing illness improve.

Is Depression Linked to Chronic Pain?

When pain lingers for weeks to months, it's referred to as being "chronic." Not only does chronic pain hurt, it also disturbs your sleep, your ability to exercise and be active, your relationships, and your productivity at work. Can you see how chronic pain may also leave you feeling sad, isolated, and depressed?

There is help for chronic pain and depression. A multifaceted program of medicine, psychotherapy, support groups, and more can help you manage your pain, ease your depression, and get your life back on track.

For in depth information, see Depression and Chronic Pain.

Does Depression Often Occur With Grief?

Grief is a common response to loss. Losses that may lead to grief include the death or separation of a loved one, loss of a job, death or loss of a beloved pet, or any number of other changes in life, such as divorce, becoming an "empty nester," or retirement. Anyone can experience grief and loss, but not everyone will experience depression. Each person is unique in how he or she copes with these feelings.