Antidepressant side effects: a plain-English guide.

This is a general explainer about the antidepressants most commonly prescribed in Australia — predominantly SSRIs (selective serotonin reuptake inhibitors) and SNRIs (serotonin-noradrenaline reuptake inhibitors). It isn't medical advice. It doesn't recommend or compare specific brands. Your prescriber will discuss the specific medication and dose that fits your situation.

The first two to four weeks

Antidepressants take time to reach their full effect — usually four to six weeks. Frustratingly, most side effects start before any benefit does. The most common early effects of SSRIs and SNRIs include:

• Mild nausea or stomach upset — usually settles within one to two weeks. Often easier if taken with food.
• Headache.
• Sleep changes — sometimes more vivid dreams, sometimes initial sleep disturbance.
• Initial increase in anxiety or restlessness — particularly with SSRIs in the first one to two weeks.
• Fatigue or, conversely, feeling 'wired'.
• Reduced appetite.

This early window is one of the reasons antidepressants are usually started at a lower dose and titrated up — the body needs time to adjust.

Ongoing side effects

Once you've been on a stable dose for a few months, the side-effect picture changes. The early stomach upset and headaches usually settle. What can persist:

• Sexual side effects — reduced libido, delayed orgasm, anorgasmia. Common with SSRIs and SNRIs and worth flagging early if it's affecting you.
• Weight changes — modest, in either direction, varies by medication and individual.
• Emotional blunting — a sense of 'flat' rather than feeling things fully. Often improves with dose adjustment.
• Sweating.
• Mild bruising or bleeding tendency in some people.

Worth calling your prescriber about

• Sustained, marked agitation or new suicidal thoughts — particularly in the first few weeks.
• Significant mood elevation (high energy, reduced need for sleep, racing thoughts, impulsive decisions) — may signal underlying bipolar features.
• Symptoms suggestive of serotonin excess: confusion, tremor, fever, rapid heart rate. Uncommon, but a medical issue.
• Severe or sustained sexual side effects that are affecting wellbeing.
• Withdrawal symptoms if you stop abruptly.

Stopping antidepressants

Most antidepressants need to be tapered down rather than stopped abruptly. Discontinuation symptoms — sometimes described as 'brain zaps', flu-like symptoms, dizziness, sleep disturbance — are uncomfortable but generally not dangerous. They're much less likely with a slow, planned taper, and your prescriber will write a plan for you when the time comes.

Monitoring and review

Best practice — consistent with RANZCP and NICE guidance — is regular review in the first three months of treatment, then at least every six months while on maintenance medication. Your prescriber will check for both response and side effects, and adjust as needed.