Starting an antidepressant: what to expect

They take weeks to work

One of the most important things to know is that antidepressants do not work straight away. While some side effects can appear in the first days, the mood-lifting benefit usually builds gradually over several weeks. This delay catches many people out: they assume the medicine is not working and feel tempted to stop just as it is starting to help. Sleep, appetite or energy sometimes improve before mood does. Sticking with it, as your prescriber advises, gives the medicine a fair chance. If after a reasonable trial you feel no better, that is a reason to go back and review — not to give up on treatment altogether — as a different medicine or approach may suit you better.

Early side effects often settle

In the first week or two, side effects are common and are often at their worst just as the benefit has not yet arrived — which is an awkward combination. With the widely used SSRIs and SNRIs, early effects can include nausea, headache, feeling restless or jittery, disturbed sleep or changes in appetite. The encouraging news is that many of these ease as your body adjusts over a couple of weeks. Taking the medicine with food can help nausea. It helps to know this in advance so the early days do not come as a shock. If side effects are severe, persistent or worrying, contact your prescriber rather than stopping suddenly — they can adjust the timing, amount or choice of medicine.

Do not stop abruptly

Antidepressants should not be stopped suddenly. Doing so can cause discontinuation symptoms — such as dizziness, flu-like feelings, "electric shock" sensations, irritability, vivid dreams or anxiety — which can be unpleasant and mistaken for the original illness returning. These are not the same as addiction; the medicine is not craved in the way addictive drugs are, but the body does adjust to it, so it needs to be reduced gradually. When the time comes to stop, your prescriber will usually taper the amount down slowly, sometimes over weeks or longer, to make it comfortable. If you ever want to come off, do it with your prescriber and a plan, rather than simply stopping.

Safety points: mood monitoring and serotonin syndrome

A few safety points are worth knowing. In the first weeks, and especially in people under twenty-five, there should be closer monitoring of mood, because occasionally distressing thoughts or restlessness can increase early on — so any worsening mood or thoughts of self-harm should be reported promptly. Separately, a rare reaction called serotonin syndrome can occur if too much serotonin builds up, usually when certain medicines are combined; warning signs include agitation, a racing heart, sweating, shivering, twitching muscles, confusion and a high temperature. It needs urgent medical attention. Always tell any prescriber or pharmacist what you take, including over-the-counter remedies and supplements such as St John's wort, before adding anything new.

They work best with support

Antidepressants are one part of treatment, not the whole of it. For many people they work best alongside talking therapies, such as cognitive behavioural therapy, and the everyday foundations that support mental health: sleep, activity, connection with others and managing stress. Medicine can lift mood enough to make these other steps possible; the steps, in turn, help the recovery last. Treatment is also individual — finding the right medicine can take some adjustment, and that is normal rather than a failure. Keep your review appointments so your prescriber can check how you are getting on. With the right combination of support, most people with depression or anxiety improve over time.