The most important thing to know about the causes of depression is that we don’t really know the answer to this question. It is generally believed that all mental disorders are caused by a complex interaction and combination of biological, psychological and social factors. This theory is called the bio-psycho-social model of causation and is the most generally accepted theory of the cause of disorders such as depression by professionals.

Some types of depression run in families, suggesting that a biological vulnerability can be inherited. This seems to be the case with bipolar disorder. Studies of families in which members of each generation develop bipolar disorder found that those with the illness have a somewhat different genetic makeup than those who do not get ill. However, the reverse is not true: Not everybody with the genetic makeup that causes vulnerability to bipolar disorder will have the illness. Apparently additional factors, possibly stresses at home, work, or school, are involved in its onset.

In some families, major depression also seems to occur generation after generation. However, it can also occur in people who have no family history of depression. Whether inherited or not, majordepressive disorder is often associated with changes in brain structures or brain function.

People who have low self-esteem, who consistently view themselves and the world with pessimism or who are readily overwhelmed by stress, are prone to depression. Whether this represents a psychological predisposition or an early form of the illness is not clear.

In recent years, researchers have shown that physical changes in the body can be accompanied by mental changes as well. Medical illnesses such as stroke, a heart attack, cancer, Parkinson’s disease, and hormonal disorders can cause depressive illness, making the sick person apathetic and unwilling to care for his or her physical needs, thus prolonging the recovery period. Also, a serious loss, difficult relationship, financial problem, or any stressful (unwelcome or even desired) change in life patterns can trigger a depressive episode. Very often, a combination of genetic, psychological, and environmental factors is involved in the onset of a depressive disorder.

Depression is not just feeling blue from time to time. Instead, depression is characterized by a long-standing, daily feeling of sadness, hopelessness, worthlessness and emptiness.

A person who experiences depression often cannot see a future for themselves. It can feel like the world is closing in around them. The warning signs and symptoms of depression are usually pretty clear to those around the person suffering — the person doesn’t seem at all like their normal self. The changes in the person’s mood are evident to friends and family.

Depression is also experienced as a loss of interest and energy in things the person normally enjoys doing, things like working, going out, or being with family and friends. Most people with depression also experience problems with eating and sleeping — either too much or too little. A depressed person’s memory and ability to concentrate will often be impaired too. The person with depression will often be more irritable or feel restless.

Warning Signs & Symptoms of Depression

Not everyone who is depressed experiences every symptom. Some people experience a few symptoms, some many. Severity of symptoms varies with individuals and also varies over time.

Depression

• Persistent sad, anxious, or empty mood
• Feelings of hopelessness, pessimism
• Feelings of guilt, worthlessness, helplessness
• Loss of interest or pleasure in hobbies and activities that were once enjoyed, including sex
• Decreased energy, fatigue, being “slowed”
• Difficulty concentrating, remembering, or making decisions
• Insomnia, early-morning awakening, or oversleeping
• Appetite and/or weight loss or overeating and weight gain
• Thoughts of death or suicide; suicide attempts
• Restlessness, irritability
• Persistent physical symptoms that do not respond to treatment, such as headaches, digestive disorders, and chronic pain

In order for depression to be diagnosed, the person must experience these symptoms every day, for at least 2 weeks.

Types of Depression

Depressive disorders come in many different types, but each type has its own unique symptoms and treatments.

Major depression, the most common type of a depressive disorder, is characterized by a combination of symptoms (see symptom list) that interfere with the ability to work, study, sleep, eat, and enjoy once pleasurable activities. Such a disabling episode of depression may occur only once but more commonly occurs several times in a lifetime. Mental health professionals use this checklist of specific symptoms to determine whether major depression exists or not. Depression is also rated by your diagnosing physician or mental health professional in terms of its severity — mild, moderate, or severe. Severe depression is the most serious type.

A more chronic type of depression, dysthymia (or dysthymic disorder), involves long-term, chronic symptoms that do not disable, but keep one from functioning well or from feeling good. Many people with dysthymia also experience major depressive episodes at some time in their lives.

Another type of depression is experienced as a part of bipolar disorder, also called manic-depressive illness. Not nearly as prevalent as other forms of depressive disorders, bipolar disorder is characterized by cycling mood changes: severe highs (mania) and lows (depression). Sometimes the mood switches are dramatic and rapid, but most often they are gradual.

Yet another type of depression is known as postpartum depression (or, more technically, peripartum depression). This most often occurs in expecting mothers, or moms who’ve recently given birth to their baby.

The last kind of depression is known as seasonal affective disorder (SAD). It occurs during the change of the seasons, mostly in the winter and summer, and is thought to be related to a decrease (or overabundance) of exposure to sunlight.

When in a cycle of depression, a person with depression can have any or all of the symptoms of a depressive disorder. When in the manic cycle, the individual may be overactive, overtalkative, and have a great deal of energy. Mania often affects thinking, judgment, and social behavior in ways that cause serious problems and embarrassment. For example, the individual in a manic phase may feel elated, full of grand schemes that might range from unwise business decisions to romantic sprees. Mania, left untreated, may sometimes even worsen into a psychotic state.