Antidepressant Side Effects: What You Need to Know Before Starting Treatment

When you start taking an antidepressant, a medication prescribed to treat depression, anxiety, and other mood disorders by balancing brain chemicals. Also known as antidepressive agents, these drugs help millions of people feel more like themselves again—but they don’t work the same for everyone. Many people expect immediate relief, but the first few weeks often bring side effects that can feel worse than the original symptoms. That’s normal. It doesn’t mean the drug isn’t working—it just means your body is adjusting.

Most SSRIs, a common class of antidepressants that increase serotonin levels in the brain. Also known as selective serotonin reuptake inhibitors like sertraline or escitalopram can cause nausea, headaches, or trouble sleeping early on. SNRIs, another major type that affect both serotonin and norepinephrine. Also known as serotonin-norepinephrine reuptake inhibitors like venlafaxine might lead to increased blood pressure or dry mouth. These aren’t rare—they happen in up to 70% of users during the first month. The good news? Most fade within two to four weeks. If they stick around longer, it’s not a sign you’re weak—it’s a sign you need to talk to your doctor about switching or adjusting.

Some side effects are trickier because they show up later. Weight gain, low sex drive, or emotional numbness can creep in after months of use. People often stop taking their meds because of these, not because they feel better—but that’s when withdrawal symptoms can hit hard. antidepressant withdrawal, a set of physical and mental symptoms that occur when stopping or reducing antidepressants too quickly. Also known as discontinuation syndrome includes dizziness, electric-shock sensations, and flu-like feelings. It’s not addiction—it’s your nervous system reacting to a sudden change. Tapering slowly under medical guidance makes a huge difference.

And don’t forget interactions. Mixing antidepressants with certain painkillers, herbal supplements like St. John’s Wort, or even grapefruit juice can be risky. Some combinations raise serotonin levels too high, leading to a rare but dangerous condition called serotonin syndrome. That’s why it’s so important to tell every doctor you see—dentist, pharmacist, ER staff—that you’re on an antidepressant. You wouldn’t skip telling them about a heart condition, so don’t skip this either.

What you’ll find below are real, no-fluff breakdowns of what happens when your body reacts to these drugs. We cover how side effects differ between medications, what to track in a journal, when to push back on your prescriber, and how to handle the emotional weight of feeling worse before you get better. No hype. No jargon. Just what actually matters when you’re trying to feel like yourself again.