A common treatment for clinical depression is a type of medication called an antidepressant. Antidepressants come in a variety of forms, but all of them work by impacting certain neurochemicals in your brain, such as serotonin and norepinephrine. Antidepressants are most commonly prescribed by a psychiatrist, but may also be prescribed by a family physician or general practitioner to treat depression.

The different classes of antidepressants include selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), norepinephrine (noradrenaline) reuptake inhibitors, atypical antidepressants, tricyclic antidepressants (TCAs), and monoamine oxidase inhibitors (MAOIs). Different classes of antidepressants take different amounts of time before you will start to feel their anti-depressant effects.

The most commonly prescribed modern antidepressants include SSRIs — such as Prozac, Lexapro, Celexa and Paxil — and SNRIs — such as Pristiq, Cumbalta and Effexor. Although the claim is made that some people may be able to start to feel less depressed within 2 weeks of taking one of these kinds of antidepressants, most people won’t start experiencing the full positive effects of the medication until 6 to 8 weeks after beginning it.

In addition to feeling less depressed from antidepressant medications, people will often experience the side effects of antidepressants first. While these side effects vary from person to person and from medication to medication, the most commonly observed side effects in antidepressants are:

  • Decreased sex drive or no sex drive at all
  • Dry mouth — your mouth feels very dry and cannot produce the same amount of saliva as usual
  • Mild to moderate nausea
  • Insomnia — inability to get to sleep, or difficulty staying asleep
  • Increased anxiousness or restlessness
  • Sleepiness
  • Weight gain
  • Constipation or diarrhea
  • Headaches
  • Increased sweating
  • Tremors or dizziness

You shouldn’t be overtly concerned if you experience any of these side effects while taking an antidepressant, but you should still tell your psychiatrist or doctor about them. Some side effects may go away on their own once your body adjusts to the medication. Others may not, and may be addressed through an adjustment of your medication dose or when you take it.

Antidepressants don’t work for everyone. Sometimes the first antidepressant a doctor prescribes may not work for you (as they don’t in 50 percent of people who try an antidepressant). Don’t get frustrated, just accept that either another medication may need to be tried, or the doctor may suggest a higher dose may be required. Talk to your doctor about adjusting your medication if you’re not feeling any positive effects of the medication after 6 to 8 weeks.

Older classes of antidepressants — MAOIs and tricyclic antidepressants — take about the same amount of time to work — anywhere from 2 to 6 weeks for most people, while most people will start to feel a benefit within 3 to 4 weeks. It is not well understood why antidepressant medications appear to take longer to work than other types of psychiatric medications.