SSRIs Explained: How Antidepressants Work

SSRIs (selective serotonin reuptake inhibitors) are the most commonly prescribed antidepressants. Over 37 million Americans take them. But how do they actually work?

How SSRIs Work

SSRIs increase serotonin availability in the brain by blocking its reabsorption (reuptake). This doesn't mean depression is simply 'low serotonin'—the reality is more complex. The increased serotonin triggers downstream changes in brain circuits and neuroplasticity.

Common SSRIs

• Fluoxetine (Prozac) - longest track record, activating
• Sertraline (Zoloft) - often first choice, versatile
• Escitalopram (Lexapro) - newer, often well-tolerated
• Citalopram (Celexa) - similar to Lexapro
• Paroxetine (Paxil) - more sedating, harder to stop

What to Expect

Week 1-2

• Side effects often peak (nausea, headache, jitteriness)
• No mood improvement yet
• Sleep and appetite may change
• This is normal and usually temporary

Week 2-4

• Side effects typically decrease
• May notice slight improvements in energy or sleep
• Full antidepressant effect not yet present

Week 4-8

• Antidepressant effects become noticeable
• Mood, motivation, and thinking often improve
• If no improvement by week 8, may need dose adjustment or different medication

Common Side Effects

Most side effects are temporary:

• Nausea (usually first 1-2 weeks)
• Headache
• Sleep changes
• Sexual side effects (can persist)
• Weight changes
• Emotional blunting (some people)

How Long to Take Them

Guidelines recommend:

• First episode: 6-12 months after feeling better
• Second episode: 2+ years
• Three or more episodes: Consider long-term/indefinite
• Always taper gradually under medical supervision

The Bottom Line

SSRIs aren't perfect, but they help millions of people. Give them adequate time to work (8+ weeks), communicate side effects to your doctor, and don't stop abruptly. They're one tool among many for treating depression and anxiety.