The causes of depression - Current theories

Depressive Illness: An Information Guide

On this page:

• The Stress-Vulnerability Model — Risk Factors in Depression
• Common questions about depression
• Common questions about acute episodes

There is no simple answer to what causes depression, because several factors may play a part in the onset of the disorder. These include: a genetic or family history of depression, psychological or emotional vulnerability to depression, biological factors, and life event or environmental stressors. The fact that you may be undertaking one type of treatment, for example antidepressant medications, does not mean your depression is entirely biological. What it does mean is that often depression can be effectively treated by focusing on one area, such as the biochemistry in the brain. The type of treatment recommended is also often influenced by the severity of your depression. If severely depressed, it is difficult for a person to undertake the “talking therapies.” As a result, medications may be the first stage of treatment, followed by psychotherapy as a second stage of intervention. Once you are feeling somewhat better, you may be better able to tolerate talking about other life problems that contribute to your depression.

Everyone has a certain number of “risk” or “vulnerability” factors. The more risk factors a person has, and the greater the levels of stress on the person, the greater the chance of having a depressive episode. This is known as the stress-vulnerability model.

The Stress-Vulnerability Model — Risk Factors in Depression

1. Genetic and family history

A family history of depression does not necessarily mean children or other relatives will develop major depression. However, those with a family history of depression have slightly higher chances of becoming depressed at some stage in their lives. There are several theories to explain this phenomenon.

Genetic research suggests that depression can run in families. Studies of twins raised separately have shown that if one twin develops the disorder, the other has a 40 to 50 per cent chance of also being affected. This rate, though it is moderate, suggests that some people may have a genetic predisposition to developing depression.

A genetic predisposition alone, however, is unlikely to cause depression. Other factors, such as traumatic childhood or adult life events, may act as triggers. The onset of depression may also be influenced by what we learn as children. Some people may have been exposed to the depressive symptoms of their parents and have learned this as a way of reacting to certain problems. As adults, they may go on to use these strategies to deal with their own life stressors. Growing up with one parent who has been depressed puts a child at a 10 per cent risk of developing the disorder. If both parents were depressed, there is a 30 per cent risk. It is important to note that these figures are actually lower than those for other types of illness that may be passed on from parent to child.

If you have a family history of depression, it is important to educate yourself about the disorder and what you can do to protect yourself against it.

2. Psychological vulnerability

Personality style, and the way you have learned to deal with problems, may contribute to the onset of depression. If you are the type of person who has a low opinion of yourself and worries a lot, if you are overly dependent on others, if you are a perfectionist and expect too much from yourself or others, or if you tend to hide your feelings, you may be at greater risk of becoming depressed.

3. Life events or environmental stresses

Some studies suggest that early childhood trauma and losses, such as the death or separation of parents, or adult life events, such as the death of a loved one, divorce, the loss of a job, retirement, serious financial problems, and family conflict, can lead to the onset of depression. Suffering several severe and prolonged difficult life events increases a person’s chances of developing a depressive disorder. Once depressed, it is common for a person to remember earlier traumatic life events, such as the loss of a parent, or childhood abuse, which make the depression worse.

Living with chronic family problems can also seriously affect a person’s mood and lead to depressive symptoms. People living in emotionally abusive or violent relationships can feel trapped, both financially and emotionally, and feel hopeless about their future. This is particularly true of mothers with young children. The ongoing stress and social isolation associated with these family circumstances can lead to depressive symptoms.

Once a person develops a serious depression, he or she may need intensive treatment before feeling able to deal with the situation or life stressors that triggered the onset of the illness.

4. Biological factors

Depression may appear after unusual physiological changes such as childbirth, and viral or other infections. This has given rise to the theory that hormonal or chemical imbalances in the brain may cause depression. Studies have shown that there are differences in the levels of certain biochemicals between depressed and non depressed subjects. The fact that depression can be helped by antidepressant medication and electroconvulsive therapy (ECT) tends to support this theory.

Seasonal affective disorder (SAD) is a good example of how biology and personality may work together to influence the onset of depression. Researchers are investigating whether chemicals in the brain that regulate mood, sleep and appetite are affected by changes in levels of light. Research has found that people suffering from SAD seem to be highly sensitive to their own feelings and events around them, and that these reactions are amplified by seasonal changes in light levels.

For many patients and families, trying to understand the various theories that explain the onset of depression can be very confusing. While research has yet to fully explain the causes of depression, it is important to know that effective treatments are still available.

Common questions about depression

What about premenstrual syndrome (PMS), menopause and depression?

Changes in the hormonal cycle of women have been linked with symptoms of depression. Before their monthly periods (premenstrual stage), women can experience changeable moods, irritability, anxiety, sleep difficulties, as well as abdominal cramps, bloating and breast tenderness. For the woman with premenstrual tension, these symptoms may last for a few days and then go away. For the woman with premenstrual syndrome, the symptoms are more severe, and disrupt routine activities. A woman who struggles with both depression and premenstrual symptoms tends to feel much worse during this time of the month.

During menopause, a period of biological changes during mid-life, women must adjust to the effects of reduced levels of the hormone estrogen. The symptoms of menopause, such as hot flashes and profound sweating, may make it harder to function at work and in social situations. Menopause is also a time when women may have to deal with psychological issues and other life events — children may be leaving home, and aging spouses and family members may develop health problems. Menopause also represents the end of a woman ’s ability to have children. The physical and emotional stressors associated with menopause may contribute to the onset of depressive symptoms.

Can depression occur secondary to a physical illness?

Yes. In the medically ill, depression can occur in three different ways. Depressive symptoms may be the result of another illness that shares the same symptoms, such as lupus or hypothyroidism. Depression may be a reaction to another illness, such as cancer or a heart attack. Finally, depression may be caused by an illness itself, such as a stroke, where neurological changes have occurred. Regardless of the cause, depression in the medically ill is often treated with antidepressants and other therapies.

Is depression treated differently in the elderly?

Yes. Generally, elderly patients are given lower dosages because they are more sensitive to medication, prone to confusion, and may have more trouble tolerating side-effects. Potential drug interactions must be considered, because elderly patients are often taking medication for other medical problems.

How do alcohol, street and prescription drugs influence depression?

Alcohol, street drugs and some prescription medications can provide a temporary break from some of the symptoms of depression. However, this “self-medication” simply masks — and sometimes worsens — the symptoms of depression, which resurface when the substance use stops. In other people, depression can be triggered by abuse of alcohol and other drugs. In both cases, the substance abuse itself can lead to further health problems and can disrupt a person’s ability to function. In most cases, treatment for the substance abuse is given first. If the depression persists, then the mood disorder becomes the focus of intervention.

Can people diagnosed with depression also suffer from anxiety?

Yes. As many as two-thirds of people who struggle with depression also have prominent symptoms of anxiety. Anxiety refers to excessive worry that is hard to control (apprehensive expectation). A person with anxiety feels restless or “keyed up and on edge.” The person may also: tire easily, feel his or her mind going blank, feel irritable, or have tense muscles, trouble concentrating and sleep problems. The combination of depressive and anxiety symptoms can severely impair a person’s ability to function at work, at school and in relationships.

If you have symptoms of both depression and anxiety, a thorough assessment should determine which of the two is the primary problem. The diagnosis will influence what kind of treatment is suggested. If it is difficult to tell which is the primary disorder, a diagnosis of mixed anxiety-depressive disorder will be made, and treatment will be prescribed accordingly.

Many of the medications used to treat depression, such as Prozac (fluoxetine) and Anafranil (clomipramine) also treat anxiety. A person might also benefit from an anti-anxiety medication or anxiolytic such as Ativan (lorazepam). Cognitive Behaviour Therapy, which is a short-term, talk therapy described in the next chapter, has been very effective in treating both depression and anxiety. Other helpful treatments include relaxation therapy, and stress management techniques.

Even though loneliness and a lack of social supports can contribute to and maintain depression, depressed people seem to make their situations worse by often avoiding other people, thereby increasing their isolation. Why is this problem so common?

Most depressed people want to be left alone. The symptoms of depression make socializing and interacting with friends and family very difficult and even stressful. Additionally, depressed people often feel guilty about being depressed, and assume that their presence cannot be tolerated by others. Unfortunately, the resulting social isolation simply reinforces their depression. Part of recovery involves encouraging people with depression to gradually reintroduce themselves to social situations and structured group activities.

Should depressed people force themselves to continue with routines and activities?

If you are mildly depressed, but still able to carry on with some or all of your regular activities, you should push yourself to do so. If there is no routine to your day, you may dwell on problems and make your depression worse. If you are severely depressed and find it physically and emotionally impossible to carry out your normal activities, you should treat your depression the same way you would treat a severe physical illness. Lower your expectations of yourself, set small goals for each day, and rest when your body needs it.

Can I return to normal after being depressed?

Most people are able to return to their previous level of functioning. For people who have suffered severe depressive episodes, or several depressive episodes, recovery can be a much slower process. Setting small, achievable goals, which may be far lower than those you would have set when you were well, will be an important first step in recovery. Professional support can help you develop a graduated plan for returning to work, school or volunteer activities.

Having had one depressive episode, will I be at risk of more periods of clinical depression?

Research suggests that people who have had one episode of depression have a 50 er cent chance of experiencing another episode at some point in their lives. After two depressive episodes there is an 80 per cent chance of relapse. While these numbers may frighten you, the best protection against relapse is the understanding that depression is an illness that must be managed over your lifetime, even during periods of health. This is why it is so important for patients, and their partners and families, to have information about the disorder and strategies for relapse prevention.

Common Questions about Acute Episodes

What should I do if I feel suicidal or feel like harming other people?

If you feel so depressed that you wish you were dead or you are thinking of ways to kill yourself or others, tell your doctor immediately. If you do not have a doctor, call you local distress centre or go for help to the emergency department of the nearest general or psychiatric hospital. It is important that you have someone with whom you can talk and who has a more objective point of view. Suicidal thinking is the result of your “depression talking,” and influencing how you see yourself and the world around you.

Will I be kept in hospital against my will if I am suicidal?

Most people who are suicidal recognize that they need treatment and find that hospitalization is a way to stay safe while their mood stabilizes. However, in most jurisdictions, if you do not recognize that you need hospitalization, or once admitted you want to leave in order to harm yourself or others, you can be legally certified by a doctor and prevented from leaving until your safety can be ensured. This certification will last only as long as is thought necessary. In most hospitals, patients may consult a rights advisor or have access to an appeal process to challenge this involuntary hospitalization.

Will I be completely well when I leave the hospital?

Probably not. Most patients are kept in hospital only in order to get their acute symptoms, such as suicidal thinking, under control and managed on medication. Then plans are made for patients to have ongoing follow up from mental health professionals in the community. Because the process of recovery is slow, and it is important for patients to resume normal routines in their homes, hospital stays are kept as brief as possible. In addition, some people with depression may feel too upset by the institutional setting, being around other ill people, and being away from family and friends to benefit from an extended hospital stay.

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