Depression is not something you can just "snap out of." It's caused by an imbalance of brain chemicals, along with other factors. Like any serious medical condition, depression needs to be treated.

Explaining Medicine offers information designed to help you get the facts on depression, clinically known as major depressive disorder.

There are almost thirty different kinds of antidepressants available today. They all work by altering the way in which certain chemicals work in our brains. These chemicals are made by our body and are called neuro-transmitters.

Neuro-transmitters are the chemicals which transmit signals between the cells in our brains. In depression, some of the neurotransmitter systems, particularly those of Serotonin and Noradrenaline, don't seem to be working properly. We think that antidepressants work by increasing the activity of these chemicals in our brains.

Studies have found that after 3 months of antidepressant treatment between 50% and 65% of the people who take them will be much improved. This compares with 25 - 30% of people given an inactive "dummy" pill, or placebo. It may seem surprising that people given placebo tablets improve, but this happens with all tablets that affect how we feel - the effect is similar with painkillers. Antidepressants do seem to be helpful but, like many other medicines, some of the benefit is due to the placebo effect.

Antidepressants are grouped by what chemicals (neurotransmitters) in the brain they affect. There are many different kinds of antidepressants:

Selective serotonin reuptake inhibitors (SSRIs)
These tend to have the least side effects compared to other antidepressants. Some side effects that can be caused by SSRIs include: dry mouth, insomnia, nausea, nervousness, sexual problems and headache.

• citalopram (brand name: Celexa)
• escitalopram (brand name: Lexapro)
• fluoxetine (brand name: Prozac)
• paroxetine (brand names: Paxil, Pexeva)
• sertraline (brand name: Zoloft)

Tricyclics
Common side effects include dry mouth, difficulty urinating, worsening of glaucoma, blurred vision, constipation, impaired thinking and tiredness. They can also affect your heart rate and blood pressure .

• amitriptyline (brand name: Elavil)
• desipramine (brand name: Norpramin)
• imipramine (brand name: Tofranil)
• nortriptyline (brand name: Aventyl, Pamelor)

Serotonin and norepinephrine reuptake inhibitors (SNRIs)
Some common side effects include nausea and loss of appetite, insomnia and tiredness, anxiety and nervousness, and headache. Dry mouth, constipation, weight loss, sexual problems, increased heart rate and increased cholesterol levels can also occur.

• venlafaxine (brand name: Effexor)
• duloxetine (brand name: Cymbalta)

Norepinephrine and dopamine reuptake inhibitors (NDRIs)
Some side effects experienced by people taking NDRIs include agitation, nausea, headache, loss of appetite and insomnia. It can also cause increased blood pressure.

• bupropion (brand name: Wellbutrin)

Combined reuptake inhibitors and receptor blockers
Side effects are drowsiness, dry mouth, nausea and dizziness. You should not take nefazodone if you have liver problems. If you have seizures, you should not take maprotiline.

• trazodone (brand name: Desyrel)
• nefazodone (brand name: Serzone)
• maprotiline
• mirtazpine (brand name: Remeron)

Monamine oxidase inhibitors (MAOIs)
MAOIs are less common than other antidepressants. They can have serious side effects, including weakness, dizziness, headaches and trembling. Taking an MAOI while you're taking another antidepressant or some over-the-counter medicines for colds and flu can cause a dangerous reaction. Your doctor will also tell you what foods and alcoholic beverages you should avoid while you are taking an MAOI. You should not take an MAOI unless you clearly understand what medications and foods to avoid. If you are taking an MAOI and your doctor wants you to start taking one of the other antidepressants, he or she will have you stop taking the MAOI for a while before you start the new medicine. This gives the MAOI time to clear out of your body.

• isocarboxazid (brand name: Marplan)
• phenelzine (brand name: Nardil)
• tranlcypromine (brand name: Parnate)

Yes and no. The older tablets (Tricyclics) are just as effective as the newer ones (SSRIs) but, on the whole, the newer ones seem to have fewer side-effects. A major advantage for the newer tablets is that they are not dangerous if someone takes an overdose of them.

More Information on Narcotic Analgesics (opioid pain killers):

MedlinePlus: Antidepressants
Drugs@FDA (CDER): Antidepressants
American Academy of Family Physicians
Wikipedia: Antidepressant

Antidepressants - Brands:

Celexa is a drug that was released by the Forest Pharmaceuticals corporation aimed at fighting depression. The FDA approved Celexa on July 17, 1998. Celexa is a member of the Selective Serotonin Reuptake Inhibitor family, which increases serotonin levels in the synapse by blocking serotonin reuptake into brain cells. The effects of this medication can usually be seen in two to three weeks, though some patients may require four or more weeks to feel better.

Lexapro [escitalopram] is an antidepressant that works by boosting levels of serotonin, one of the chief chemical messengers in the brain. The drug is a close chemical cousin of the antidepressant medication Celexa. Other antidepressants that work by raising serotonin levels include Paxil, Prozac, and Zoloft.

Luvox is the brand name for Fluvoxamine, an antidepressant and antiobsessional drug. Luvox is a Serotonin Reuptake Inhibitor (SSRI). It is often prescribed for Obsessive Compulsive Disorder (OCD). This drug is used to relieve anxiety and unpleasant thoughts that cause a person to repeat certain tasks.

Paxil (Paroxetine) is an antidepressant used to treat major depression, panic attacks, obsessive compulsive disorders (OCD), social anxiety disorder (social phobia), and generalized anxiety disorder.

Prozac is an antidepressant often prescribed to treat obsessive-compulsive disorder. An obsession is a thought that won't go away; a compulsion is an action done over and over to relieve anxiety. The drug is also used in the treatment of bulimia (binge-eating followed by deliberate vomiting). It has also been used to treat other eating disorders and obesity.

Remeron is a medication that was approved by the Food and Drug Administration (FDA) for the treatment of depression in June 1997. Remeron was the first drug in a new class of antidepressants with a unique ability to target specific serotonin receptors. Along with its efficacy in the treatment of moderate to severe depression, Remeron has proven to be effective for treating anxiety, motor retardation, and cognitive and sleep disturbances associated with depression.

Wellbutrin is a relatively new antidepressant medication and is prescribed to help relieve certain kinds of major depression. As with other antidepressants, it is unknown exactly how Wellbutrin works. Scientists believe that Wellbutrin treats depression by affecting two chemicals in the brain called dopamine and norepinephrine. These are two of the chemicals that are believed to help regulate your mood.

Zoloft is an antidepressant drug that was released by the Pfizer corporation in 1991 which aimed at fighting depression. The FDA approved Zoloft in October of 1997. Zoloft is a member of the Selective Serotonin Reuptake Inhibitor family, which increases serotonin levels in the synapse by blocking serotonin reuptake into brain cells.