‘The side effects of Prozac made me think I was going mad – but here’s why I’m still taking it’

In the six years I’ve worked for The Mail on Sunday I’ve recovered from an eating disorder, had several bouts of severe anxiety, moved twice and got married. Now I’m getting divorced.

Yet until the end of last year, I hadn’t taken a single day off for mental health reasons — and it had nothing to do with this.

In fact, my breakdown was caused by the pills I took to help me deal with the stress of the above.

It happened in September, two weeks after I started taking the antidepressant Prozac, also known by its generic name fluoxetine.

I had decided to take the medication when my anxiety symptoms—palpitations, chest tightness, stomach knots—began to make everyday life difficult.

My collapse was caused by the pills I took to help me deal with the stress of the above, writes Mail on Sunday deputy health editor Eve Simmons

Like eight million others in the UK, for most of my 31 years I’ve suffered from anxiety attacks, intermittent, usually triggered by stress. I’ve been given Prozac – one of the most commonly prescribed antidepressants – twice before, during my teens and early twenties, to treat anxiety. But this most recent time felt something different. Within two weeks of starting treatment, I started to feel… a little bad.

I was at a friend’s birthday barbecue. It was a lovely day—warm weather, pots of dip, and three types of sausage—but I was starting to feel like someone had started a fire in my chest, or how I imagine it would feel to be held at gunpoint. My body was stiff, anxious thoughts racing.

I came home afterwards and collapsed on the couch, cried, and then spent two hours Googling things like “How can you turn off your mind?” and “How do you know if you have schizophrenia?”

Even more disturbing, I developed the feeling of dissociation – a feeling that the body is separate from the mind. Actually, I thought I was going crazy.

After a minimal night’s sleep, I called my MoS Health colleagues the next morning and admitted for the first time that I wasn’t well.


According to NHS data, an estimated 21 million antidepressants were prescribed between January and March 2022.

I’m not ashamed to talk about my mental health, but my work has always been something of a haven for my troubled mind.

This time I couldn’t do anything – write, read or understand. Information just wasn’t coming in.

My editor insisted that I take as much time as I needed.

What followed was a frantic phone call to the doctor, who prescribed a low dose of the sedative diazepam and told me to call back in a few days. “It’s very common for fluoxetine to make you feel worse at first,” he told me, “but the side effects usually go away in a month or two.”

Could I feel this way for two months? I wasn’t sure if I would make it to the next day.

In light of all this, you may be surprised that today I remain a staunch advocate of Prozac and all antidepressants. I’m still taking the pills.

The doctor was right. The side effects subsided after about a month and the treatment has kept me going through a turbulent time in my life. But as a health journalist who has written extensively about the benefits of antidepressants, I was blown away.

In November I received a series of criticisms after writing in these pages that my pediatrician first prescribed Prozac when I was just 15, to treat severe anxiety. On Twitter, some accused me of pushing powerful drugs on teenagers known for side effects such as suicidal thoughts.

According to official guidelines, antidepressants may only be prescribed to young people under the age of 18 by a psychiatrist, and only in serious cases. I immediately responded, arguing that the evidence showed that antidepressants generally do more good than harm — and even for teens, they can save lives. But had my own recent experience proved me wrong?

The most commonly prescribed antidepressants in the UK are selective serotonin reuptake inhibitors or SSRIs.

Several reviews, looking at hundreds of studies, found that, on average, about 40 to 50 percent of people with depression and anxiety who take SSRIs see an overall improvement in mental health. About half of patients experience at least one side effect. In one in ten these problems are so severe that they stop.

Side effects vary by drug, but most often include fatigue, nausea, dizziness, upset stomach, sexual problems, and severe agitation/anxiety. According to the American Medical Association, about four percent of patients experience suicidal thoughts.

But there is little clear information on how long these problems will last. Guidelines from the UK’s drug watchdog, the National Institute for Health and Care Excellence (NICE), make vague mentions and state that the pills should work within four weeks, while some side effects “may persist during treatment”. But GPs I have spoken to say they see a clear trend.

“It can take about three weeks to a month for you to feel normal again,” said Dr. Ellie Cannon, The Mail on Sunday’s GP columnist, who added that she also experienced short-term side effects when taking SSRIs. “They made me feel really out of sorts for the first few weeks, and when I adjust the dose, it can feel like I’m going crazy.”

Like eight million others in the UK, for most of my 31 years I've suffered from anxiety attacks, intermittent, usually triggered by stress.  I've been given Prozac (pictured) - one of the most commonly prescribed antidepressants - twice before, during my teens and early 20s, to treat anxiety

Like eight million others in the UK, for most of my 31 years I’ve suffered from anxiety attacks, intermittent, usually triggered by stress. I’ve been given Prozac (pictured) – one of the most commonly prescribed antidepressants – twice before, during my teens and early 20s, to treat anxiety

Dr. Clare Gerada, a psychiatrist and president of the Royal College of GPs, said: ‘Patients definitely feel worse in the first three weeks. They tend to get very severe anxiety symptoms. Sometimes I prescribe a sleeping tablet in the first week to help patients deal with heightened panic at night.

“But if they stay on the antidepressants, things usually get better.”

Dr. Penny Ward, visiting professor of pharmaceutical medicine at King’s College London, says there are several possible explanations. “The chemical combination in some SSRIs has a domino effect on other connections in the brain and the rest of the body,” she says.

SSRIs turn off the body’s ability to dampen serotonin [a neurotransmitter that carries messages between nerve cells in the brain and the rest of the body].

“This could have an impact on the central nervous system, which controls our natural fear response and could, in theory, exacerbate anxiety.” But once serotonin reaches a level that improves mood, anxiety becomes less of a nuisance.”

Few studies track the duration of specific side effects, but many do report that many patients stop taking the pills because of side effects, and when.

In a study of more than 600 patients, only 15 percent said serious side effects led them to stop taking the pills within the first three months, even though 60 percent had serious side effects in the first week. Another US study of 400 patients found that 40 percent had drowsiness, 30 percent had sexual problems (such as erectile dysfunction), 22 percent had insomnia, and 19 percent had anxiety.

In about two-thirds of cases, symptoms were only a problem for the first two weeks.

But some SSRIs are associated with more early side effects than others – and fluoxetine appears to be one of the worst offenders.

“I would always prefer not to prescribe fluoxetine,” says Dr. Gerada. ‘You see a lot more anxiety compared to other SSRIs.

“In the beginning you get a feeling of irritability and restlessness, because it has a slightly stimulating effect.”

A number of doctors I’ve spoken to over the years have told me that patients often find that antidepressants don’t work because they stop too soon. Studies show that about 60 percent of people see benefits after three months, compared to 40 percent after one month.


Some of the rarer side effects of SSRI drugs include flu-like symptoms, trouble going to the toilet, and irregular heart rhythm.

The message is, if you can, try to stick to it. “Ask a loved one to keep a close eye on you for the first few weeks,” says Dr. Cannon.

And if not, try something else. In 2008, experts at Pittsburgh University found that 40 percent of a group of 334 depressed patients saw an improvement in mental health after switching SSRIs.

But doctors say these drugs are not everything. There are drug classes that act on various brain chemicals to improve mood and reduce anxiety.

For example, SNRIs, which affect another mood-related brain chemical called norepinephrine, may be effective in people who can’t get along with SSRIs, especially venlafaxine. There are also older classes of antidepressants such as tricyclic antidepressants, including amitriptyline and nortriptyline – although these come with side effects such as drowsiness and falls.

A 2018 review by researchers at the University of Oxford compared clinical trial dropout rates — the proportion of patients who stop taking a treatment before the trial is over — and the efficacy of 21 different antidepressants.

The ones that came out on top were, oddly enough, atypical antidepressants, including agomelatine, which increases production of the hormone melatonin, mirtazapine, and a tricyclic antidepressant called clomipramine. But all the drugs studied, including SSRIs, were found to be effective.

I’ve been on Prozac for six months now, around the time doctors suggest coming off it when you feel better. And while I feel much less disturbed, with a challenging year ahead, I’d rather not risk letting my brain marinate in its natural juices.

I’m aware there’s a chance I could use them for the next two, three, or even five years, but as long as I get out of bed in the morning, I honestly don’t mind.