There is no single cause of depression. Rather, it usually results from a combination of factors such as an imbalance of brain chemicals, family history, thoughts or beliefs that increase the risk of depression, and traumatic or stressful life events.

One factor involved in depression is an imbalance of the chemicals that help send messages in the brain. These chemicals in our brain also help regulate our emotions, behaviours, and thinking. How we perceive the world and what happens to us can also contribute to depression.

Depression has a genetic component (i.e., family history). While the tendency to be depressed can be genetically inherited, the onset of depression can be provoked by many factors.

Triggers of depression include:

• difficult or traumatic life changes (such as losing a loved one, ending a relationship, losing a job)
• medical conditions such as Parkinson's disease, stroke, lupus, hypothyroidism, chronic pain, and some types of cancer
• use of certain medications, including corticosteroids, anabolic steroids, narcotics, benzodiazepines, progesterone (found in some female hormonal pills), and street drugs such as amphetamines
• alcohol, which has short-term and possibly long-term depressive effects

It is important to recognize that depression is not something you can "get over" on your own, and it is not the result of personal weakness or an inability to cope.

Although we all feel sad sometimes, clinical (major) depression is diagnosed when a person experiences at least 5 of the symptoms below (one of which must be depressed mood or loss of interest or pleasure in daily activities), on most days for at least 2 weeks:

• depressed mood (sadness)
• loss of interest or pleasure in daily activities
• changes in appetite or weight
• fatigue or loss of energy
• insomnia (trouble sleeping) or chronic oversleeping
• noticeable changes in activity level (agitated or slowed down)
• feelings of worthlessness or guilt
• difficulty concentrating or making decisions
• difficulty remembering things
• recurring thoughts of death or suicide

Other symptoms of depression may include:

• loss of interest in work and other activities
• avoiding family members and friends
• irritability
• crying easily
• outbursts of anger
• hallucinations (hearing or seeing things that aren't there)
• delusions (having thoughts that are not based on reality)
• body aches and pains, such as headache, joint pain, or abdominal pain (these symptoms may be reported rather than feelings of sadness)

Clinical depression may vary in its severity, and in its extreme forms (i.e., thoughts of suicide) it can be life-threatening and require immediate medical attention.

Symptoms of other forms of depression, although generally milder, may still negatively affect a person's daily activities and quality of life.

A person with depression is at an increased risk of obesity, alcohol or drug abuse, anxiety, pain, or physical illness.

To diagnose depression, your doctor will ask you questions about the symptoms you are experiencing and their severity. Your doctor may perform a physical exam and order blood tests to make sure there isn't an underlying medical cause for your symptoms.

Physicians are trained to help you, and to take depression and its treatment seriously. Together with your doctor, you can begin to identify and manage the nature of the problem, and then develop a treatment plan. This may include a referral to a psychiatrist or psychotherapist.

Most types of depression respond to antidepressant medications, psychotherapy, or a combination of both. Providing education about depression and its treatment to people with depression and to their family members may also be part of a treatment plan.

Medications: Sometimes people with depression are unaware that medications can help them, or they are at first hesitant to take antidepressant medications to manage their condition. However, there are many different medications available today to help treat depression. You and your doctor can work together to decide what medication is best for you.

Some of the more commonly used medications for depression include SSRIs (selective serotonin reuptake inhibitors such as fluoxetine*, paroxetine, citalopram, and escitalopram), SNRIs (serotonin-norepinephrine reuptake inhibitors such as duloxetine, venlafaxine, and desvenlafaxine), bupropion, trazodone, mirtazapine, MAOIs (monoamine oxidase inhibitors such as moclobemide and phenelzine), and tricyclic antidepressants (e.g., amitriptyline, doxepin, nortriptyline).

Medications used to treat depression begin to work after 2 to 4 weeks of treatment, although improvements in some symptoms may be seen within the first few weeks. In some situations, more than one medication will need to be tried until the most appropriate one is found for an individual. All medications, including antidepressants, can have side effects. Your doctor and pharmacist should explain common side effects to you and help you to manage them should they occur. Most antidepressants should be taken for at least one year after the first episode of depression, and for at least 2 years after 2 or more episodes. Do not abruptly stop taking your antidepressant without talking to your doctor. For most of these medications, your dose will need to be decreased slowly to avoid withdrawal symptoms.

Herbals: Studies have shown that St. John's wort is not effective for people with clinical (major) depression. Although people with mild symptoms may receive some benefit from it, you should talk to your doctor and pharmacist before taking any herbals or over-the-counter medications. Keep in mind that some herbal medications may interact with prescription or over-the-counter medications, and St. John's wort may cause severe and harmful interactions with certain medications.

Psychotherapy: Psychotherapy can be an important part of managing depression. Psychiatrists, psychologists, and some family doctors are trained to help people recognize and overcome the kind of thinking that causes depression. Support groups, friends, and family can also help.

Other treatments:

• In more severe cases, electroconvulsive therapy (ECT) is used, but it is generally reserved for those who do not respond to medications.
• Light therapy (or "phototherapy," which involves controlled exposure to artificial sunlight) can help some people overcome symptoms associated with seasonal affective disorder.
• Physical activity and sports can improve depression by helping to relieve anxiety, increase appetite, aid sleep, and improve mood and self-esteem. Exercise also increases the body's production of endorphins, a natural mood-elevating hormone.
• An active lifestyle, supportive family and friends, and a positive outlook can go a long way in coping with depression.