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. No one knows exactly what causes it, but it can occur 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 increase the vulnerability to clinical depression later in life.
Certain medications. Some drugs, such as isotretinoin (used to treat acne), the antiviral drug interferon-alpha, and corticosteroids, can increase your risk of depression.
Conflict. Depression in someone who has the biological vulnerability to develop 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, may increase the risk of depression.
Genetics. A family history of depression may increase the risk. It’s thought that depression is a complex trait, meaning that there are probably many different genes that each exert small effects, rather than a single gene that contributes to disease risk.
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. However, the syndrome of clinical depression is never just a “normal” response to stressful life events.
Other personal problems. Problems such as social isolation due to other mental illnesses or being cast out of a family or social group can contribute to the risk of developing clinical depression.
How Is Biology Related to Depression? Researchers have noted differences in the brains of people who have a clinical depression as compared to those who do not. For instance, the hippocampus, a small part of the brain that is vital to the storage of memories, appears to be smaller in some people with a history of depression than in those who’ve never been depressed. A smaller hippocampus has fewer serotonin receptors. Serotonin is one of many brain chemicals known as neurotransmitters that allow communication across circuits that connect different brain regions involved in processing emotions.
How Is Genetics Linked to the Risk of Depression? We know that depression can sometimes run in families. This suggests that there’s at least a partial genetic link to depression. Children, siblings, and parents of people with severe depression are somewhat 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 the evidence of a family link to depression, it is unlikely that there is a single “depression” gene, but rather, many genes that each contribute small effects toward depression when they interact with the environment.