Depression affects about 121 million people worldwide and is a leading cause of disability, according to the World Health Organization (WHO).
"In my experience as a practicing psychiatrist, I've seen that many people with depression don't realize that they have the condition or that it's treatable," says Mitchell Mathis, M.D., deputy director of the Division of Psychiatry Products at the Food and Drug Administration (FDA).
Some who suffer from depression don't recognize the symptoms, or they attribute them to lack of sleep or a poor diet. Others realize they are depressed, but they feel too fatigued or ashamed to seek help.
Not all depression requires treatment with medication.
Medical professionals generally base a diagnosis of major depressive disorder on the presence of certain symptoms listed in the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Diagnosis depends on the number, severity, and duration of these symptoms:
depressed mood
loss of interest or pleasure in almost all activities
changes in appetite or weight
disturbed sleep
slowed or restless movements
fatigue, loss of energy
feelings of worthlessness or excessive guilt
trouble in thinking, concentrating, or making decisions
recurring thoughts of death or suicide
Antidepressants work to normalize naturally occurring brain chemicals called neurotransmitters—primarily serotonin, norepinephrine, and dopamine. Scientists have found that these particular chemicals are involved in regulating a person's mood.
There are several different classifications of antidepressants:
Selective Serotonin Reuptake Inhibitors (SSRIs): Examples are Prozac (fluoxetine), Celexa (citalopram), and Paxil (paroxetine).
Serotonin and Norepinephrine Reuptake Inhibitors (SSNIs): Examples are Effexor (venlafaxine) and Cymbalta (duloxetine).
Tricyclic antidepressants (TCAs): Examples are Elavil (amitriptyline), Tofranil (imipramine), and Pamelor (nortriptyline).
Monoamine Oxidase Inhibitors (MAOIs): Examples are Nardil (phenelzine) and Parnate (tranylcypromine).
There are other antidepressants that don't fall into any of these classifications and are considered unique, such as:
Remeron (mirtazapine)
Wellbutrin (bupropion)
The antidepressant medications in each classification affect different neurotransmitters in particular ways. For example, SSRIs increase the production of serotonin in the brain. MAOIs block monoamine oxidase, an enzyme that breaks down neurotransmitters. Blocking their breakdown means that neurotransmitters remain active in the brain. Research is ongoing to determine antidepressants' exact mechanism of action on a person's brain.
So how does a physician determine which antidepressant to prescribe? Doctors typically use a patient history and a mental status exam. With this information, the doctor can evaluate symptoms, rule out medical causes of depression, and decide if the criteria are met for major depressive disorder.
"In my opinion, it's best when antidepressant medications are personalized," says Mathis. "For example, some depressed people have difficulty sleeping. So they would benefit from a more sedating antidepressant at night. Other people with depression sleep too much and would benefit from a more activating antidepressant in the morning."
It's important to communicate how you are feeling so that your physician can evaluate the medication's effectiveness.
Approximately 60 to 70 percent of patients respond to the first antidepressant that is prescribed or to an increased dosage of that drug, according to Mathis.
But patients must take regular doses of a prescribed antidepressant for at least 3 to 4 weeks before they are likely to experience the full therapeutic effect. And if patients start to feel better, they should not stop taking the antidepressant.
"Even if you start to feel better, you may be in between episodes," says Mathis. "Depression tends to be chronic and requires everyday treatment just like high blood pressure."
If you get used to an antidepressant and just quit it, you may experience some withdrawal symptoms such as anxiety and irritability. Worst of all, depression may recur.
Patients should continue taking an antidepressant for 6 to 12 months, or in some cases longer, according to the National Institute of Mental Health (NIMH). This gives medication time to be effective and can help prevent a relapse of the depression. Patients should carefully follow their doctor's instructions.
Mathis estimates that about 10 percent of depressions are treatment resistant and won't respond to prescribed antidepressants.
That means that 20 to 30 percent of patients may not respond to the first antidepressant that is prescribed for them. NIMH-funded research has shown that patients who did not get well after taking a first medication increased their chances of becoming symptom-free after they switched to a different medication or added another medication to their existing one.
With appropriate treatment, many people with depression experience improvement of their symptoms and return to living normal and productive lives.
