Treatment for major depressive disorder (also known as major depression, clinical depression, unipolar depression, or MDD) depends on the individual and the severity of the illness. However, doctors often discover the best results when both prescription medications, such as antidepressants, and psychotherapy are used in combination.

Currently, more than two-dozen antidepressant medications are available.

Antidepressants are successful in treating depression, but no single medication has been shown to be the most effective — it depends entirely on the patient and their individual circumstances. You’ll have to take the medication regularly for several weeks in order to see results and observe any side effects.

Here are the most frequently prescribed antidepressant medicines and their most common side effects.

The typical course of treatment for depression initially begins with a prescription for a selective serotonin reuptake inhibitor (SSRI).

When the brain doesn’t make enough serotonin, or it can’t use existing serotonin correctly, the balance of chemicals in the brain may become uneven. SSRIs work to change the level of serotonin in the brain.

Specifically, SSRIs block the reabsorption of serotonin. By blocking the reabsorption, neurotransmitters may send and receive chemical messages more effectively. This is thought to increase the mood-boosting effects of serotonin and improve depression symptoms.

The most common SSRIs include:

  • fluoxetine (Prozac)
  • citalopram (Celexa)
  • paroxetine (Paxil)
  • sertraline (Zoloft)
  • escitalopram (Lexapro)
  • fluvoxamine (Luvox)

The most common side effects experienced by people who use SSRIs include:

  • digestive problems, including diarrhea
  • nausea
  • dry mouth
  • restlessness
  • headaches
  • insomnia or drowsiness
  • decreased sexual desire and difficulty reaching orgasm
  • erectile dysfunction
  • agitation (jitteriness)

Serotonin-norepinephrine reuptake inhibitors (SNRIs) are sometimes called dual reuptake inhibitors. They work by blocking the reuptake, or reabsorption, of serotonin and norepinephrine.

With additional serotonin and norepinephrine circulating in the brain, the brain’s chemical balance may be reset, and neurotransmitters are thought to communicate more effectively. This may improve mood and help relieve symptoms of depression.

The most commonly prescribed SNRIs include:

  • venlafaxine (Effexor XR)
  • desvenlafaxine (Pristiq)
  • duloxetine (Cymbalta)

The most common side effects experienced by people who use SNRIs include:

  • increased sweating
  • increased blood pressure
  • heart palpitations
  • dry mouth
  • fast heart rate
  • digestive problems, typically constipation
  • changes in appetite
  • nausea
  • dizziness
  • restlessness
  • headache
  • insomnia or drowsiness
  • decreased libido and difficulty reaching orgasm
  • agitation (jitteriness)

Tricyclic antidepressants (TCAs) were invented in the 1950s, and they were among the earliest antidepressants utilized to treat depression.

TCAs work by blocking the reabsorption of noradrenaline and serotonin. This may help the body prolong the mood-boosting benefits of the noradrenaline and serotonin it releases naturally, which can improve mood and reduce the effects of depression.

Many doctors prescribe TCAs because they’re thought to be as safe as newer medicines.

The most commonly prescribed TCAs include:

  • amitriptyline (Elavil)
  • imipramine (Tofranil)
  • doxepin (Sinequan)
  • trimipramine (Surmontil)
  • clomipramine (Anafranil)

Side effects from this class of antidepressants tend to be severe. Men tend to experience fewer side effects than women.

The most common side effects experienced by people who use TCAs include:

  • weight gain
  • dry mouth
  • blurred vision
  • drowsiness
  • fast heartbeat or irregular heartbeat
  • confusion
  • bladder problems, including difficulty urinating
  • constipation
  • loss of sexual desire

Currently only one NDRI is FDA approved for depression.

  • buproprion (Wellbutrin)

The most common side effects experienced by people who use NDRIs include:

  • seizures, when taken at high doses
  • anxiety
  • hyperventilation
  • nervousness
  • agitation (jitteriness)
  • irritability
  • shaking
  • trouble sleeping
  • restlessness

Monoamine oxidase inhibitors (MAOIs) are medications that are typically prescribed only when several other medications and treatments have failed.

MAOIs prevent the brain from breaking down the chemicals norepinephrine, serotonin, and dopamine. This allows the brain to maintain higher levels of these chemicals, which may boost mood and improve neurotransmitter communications.

The most common MAOIs include:

  • phenelzine (Nardil)
  • selegiline (Emsam, Eldepryl, and Deprenyl)
  • tranylcypromine (Parnate)
  • isocarboxazid (Marplan)

MAOIs tend to have multiple side effects, many of them serious and harmful. MAOIs also have the potential for dangerous interactions with foods and over-the-counter medications.

The most common side effects experienced by people who use MAOIs include:

  • daytime sleepiness
  • insomnia
  • dizziness
  • low blood pressure
  • dry mouth
  • nervousness
  • weight gain
  • reduced sexual desire or difficulty reaching orgasm
  • erectile dysfunction
  • bladder problems, including difficulty urinating

For treatment-resistant depression or for patients who continue to have unresolved symptoms, a secondary medication may be prescribed.

These add-on medications are generally used to treat other mental health disorders and may include anti-anxiety medications, mood stabilizers, and antipsychotics.

Examples of antipsychotics that have been approved by the Food and Drug Administration (FDA) for use as add-on therapies for depression include:

  • aripiprazole (Abilify)
  • quetiapine (Seroquel)
  • olanzapine (Zyprexa)

The side effects of these additional medications can be similar to other antidepressants.

Atypical medications, or those that don’t fit into any of the other drug categories, include mirtazapine (Remeron) and trazodone (Oleptro).

The main side effect of these medications is drowsiness. Because both of these medicines can cause sedation, they’re typically taken at night to prevent attention and focus problems.