Reviewed by: Yang Xueling (Zhujiang Hospital, Southern Medical University)
Ever wondered what causes depression? Why some people are depressed and some people are not.
Depression is an extremely complex disease. No one knows the exact cause, but depression can be caused by a combination of factors.
Some people develop depression in the course of a major illness; some people have depression due to changes such as moving or the death of a loved one; some people have a family history of depression; and some people have depression for no reason and feel unbearable due to sadness and loneliness.
1. What are the main causes of depression?
There are many factors that can increase the risk of depression, including the following.
mistreat. Past physical, sexual, or emotional abuse can increase the likelihood of depression later in life.
Specific medications. Some drugs, such as isotretinoin (used to treat acne), antiviral interferon α, and corticosteroids, can increase the risk of depression.
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conflict. Depression that occurs in people with a physiological tendency to be depressed may stem from personal conflicts or disputes with family members or friends.
The death or loss of a loved one. The death or loss of a loved one can cause grief and grief, which is normal, but it can also increase the risk of depression.
heredity. A family history of depression increases the risk. Depression is often thought of as a complex disease, meaning that there may be many different genes that each play a small role, rather than a single gene that causes the risk of the disease.
Like most mental disorders, depression is not as simple or straightforward as a simple genetic disorder such as Huntington's disease or cystic fibrosis.
Significant events. Positive events such as starting a new job, graduating, getting married, etc. can cause depression, and moving, losing one's job or losing one's income, divorce or retirement can also cause depression. However, depression is by no means just a "normal" response to an intense life event.
Other personal issues. Problems with social isolation or expulsion from a family or social group due to mental illness increase the risk of depression.
Major illness. Sometimes depression coexists with one major illness or may be triggered by another.
Substance abuse such as drugs. Approximately 30% of people with drug, alcohol, and substance abuse problems also suffer from major depressive disorder.
2. What is the connection between biology and depression?
The researchers found that the brains of depressed patients were different from those of people who did not have depression. For example, the hippocampus, a small part of the brain region that is essential for memory storage, appears to be smaller in some people with a history of depression than in people who have never experienced depression.
Small hippocampus contains fewer serotonin receptors. Serotonin receptors are known as one of many brain chemicals of neurotransmitters that enable circuits connecting different areas of the brain involved in emotional processing to communicate.
Scientists don't yet understand why some depressed people have smaller hippocampal bodies. Some researchers have found that people with depression produce a lot of the stress hormone cortisol.
Researchers believe that cortisol has a toxic or "atrophic" effect on the development of the hippocampus. Some experts have theorized that depressed people are born with a small hippocampus and are therefore predisposed to depression.
There are many other brain regions that are thought to be involved in depression, as well as pathways between specific regions. It is therefore quite possible that there is no single brain structure or pathway that can thoroughly explain depression.
But what is certain is that depression is a complex disease that is affected by many factors.
Recent scans and studies of brain structure and function have found that antidepressants can exert a "neurotrophic effect," meaning that they can maintain nerve cells, prevent cell death, and enable them to build stronger connections that can withstand biological stress.
As scientists' understanding of the causes of depression continues to deepen, health professionals will make better "customized" diagnoses, which will allow them to develop more effective treatment plans.
3. How is heredity associated with depression risk?
We know that depression is sometimes inherited within families. This suggests that depression is at least genetically correlated. Children, siblings, and parents in people with severe depression are more likely to develop depression than the average family member.
Multiple genes that interact in specific ways may contribute to different types of depression that are inherited in the family. Although there is evidence that depression is familial, it is unlikely that a single "depression" gene exists; it is more likely that there are multiple genes that, when interacting with the environment, each of which exerts a small effect on depression.
4. Can drugs cause depression?
In some populations, medications may cause depression. For example, medications such as barbiturates, benzodiazepines, and acne drugs isotretinoin are sometimes associated with depression, especially in older adults.
Similarly, corticosteroids, opioids (codeine, morphine), and anticholine drugs used to relieve stomach cramps can sometimes cause mood changes and fluctuations.
5. What is the connection between depression and chronic diseases?
In some populations, chronic diseases can cause depression. Chronic diseases can last very long and are often impossible to cure completely. However, chronic diseases can often be controlled through diet, exercise, lifestyle habits, and medications.
Some chronic diseases that can cause depression include diabetes, heart disease, arthritis, kidney disease, AIDS, lupus, and multiple sclerosis (MS). Hypothyroidism may cause depressive mood.
Researchers believe that treating depression can sometimes make co-existing diseases better.
6. Is depression related to chronic pain?
When the pain persists for weeks or even months, it can be called "chronic." Chronic pain not only creates pain sensations, but also disrupts sleep, exercise, and mobility, disrupts relationships, and reduces productivity.
For chronic pain and depression, there are coping methods, including medications, psychotherapy, support groups, and other aspects of multidimensional medication programs that can help treat pain, relieve depression, and get life back on track.
7. Does depression often go hand in hand with sadness?
Grief is a normal response to loss. Losses that lead to grief include the death or separation of a loved one, unemployment, death or loss of a pet, or other life changes such as divorce, becoming an "empty nester," or retirement.
Anyone has had grief and loss of a loved one, but not everyone develops clinical depression. Clinical depression is different from sadness: depression includes a range of other symptoms, such as feelings of worthlessness, pessimism about the future, and suicide, while sadness includes feelings of emptiness, loss, and nostalgia for loved ones whose ability to feel happy is unaffected. Everyone treats these emotions differently.
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