‘The side effects of Prozac made me think I was going crazy

By Eve Simmons, Deputy Health Editor for The Mail on Sunday

Updated: 09:27 19 March 2023

In the six years I worked for The Mail on Sunday I recovered from an eating disorder, suffered from several bouts of severe anxiety, moved house twice and am married. Now I am getting divorced.

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

In fact, my crisis was caused by the pills I was taking to help me cope 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 medication when my anxiety symptoms – pounding heart, tight chest, knotted stomach – had started to complicate my daily life.

My crisis was caused by the pills I was taking to help me cope with the stress of the above, writes Eve Simmons, deputy editor of the Mail on Sunday.

Like eight million others in the UK, I suffered from bouts of anxiety, on and off, for most of my 31s, usually triggered by stress. I’ve been prescribed Prozac – one of the most commonly prescribed antidepressants – twice before, during my teens and early 20s, to treat anxiety. But this last time, something seemed different. Within a fortnight of starting the treatment, I started to feel…a bit withdrawn.

I was at a friend’s birthday barbecue. It was a delightful day – hot weather, pots of dip and three kinds of sausage – but I started to feel like someone had started a fire in my chest, or how I imagine that might be. to be held at gunpoint. My body was rigid, anxious thoughts were racing.

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

More alarmingly, I developed the feeling of dissociation – a feeling that the body is separate from the mind. Basically, I thought I was going crazy.

After minimal sleep, the next morning I called my colleagues at MoS Health and for the first time admitted that I was unwell.


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

I’m not ashamed to talk about my mental health, but my job has always been something of a sanctuary from my troubled mind.

This time I couldn’t do anything – write, read or understand. The information just didn’t come in.

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

What followed was a frantic call to the doctor, who prescribed me a low dose of the sedating 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 within a month or two.”

Could I feel like this for two months? I wasn’t sure I would get there the next day.

In light of all of this, you may be surprised that today I remain a staunch supporter of Prozac and all antidepressants. I still take the pills.

The GP was right. The side effects subsided after about a month and the treatment kept me afloat through a hectic time in my life. But, as a health journalist who has written prolifically about the benefits of antidepressants, I was bowled over by my blip.

In November I received a series of criticisms after writing in these pages that my childhood GP had first prescribed me Prozac when I was only 15, to treat severe anxiety . On Twitter, some have accused me of offering strong drugs to teenagers known to have side effects such as suicidal thoughts.

According to official guidelines, antidepressants should only be prescribed to those under 18 by a psychiatrist, and only in severe cases. I immediately responded, arguing that the evidence showed that, overall, antidepressants do more good than harm – and even for teenagers, they can be lifesaving. 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, have found that on average, about 40-50% of people with depression and anxiety who take SSRIs experience an overall improvement in their mental health. About half of patients will experience at least one side effect. For one in ten, these problems are so serious that they stop taking them.

Side effects differ from drug to drug, but mainly include fatigue, nausea, dizziness, upset stomach, sexual problems, and severe restlessness/anxiety. About four percent of patients have suicidal thoughts, according to the American Medical Association.

But there is little clear information on how long these problems last. Advice from Britain’s medicines watchdog, the National Institute for Health and Care Excellence (NICE), makes a vague mention that the pills should take effect within four weeks, while some side effects “may persist for as long as throughout the treatment. But GPs I’ve spoken to say they’ve noticed a clear trend.

“It can take around three weeks to a month before you feel normal again,” said The Mail on Sunday GP columnist Dr Ellie Cannon, who added that she had also experienced side effects from short duration when taking SSRIs. “They made me feel very uncomfortable for the first few weeks, and if I adjust the dose, I feel like I’m going crazy.”

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

Dr Clare Gerada, psychiatrist and president of the Royal College of GPs, said: “Patients feel absolutely worse in the first three weeks. They tend to have very severe anxiety symptoms. I sometimes prescribe a sleeping pill the first week to help patients cope with increased panic at night.

“But if they stick with 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 of certain SSRIs has a knock-on effect on other compounds 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 impact the central nervous system, which controls our natural fear response and could, in theory, exacerbate anxiety.” But once serotonin reaches a mood-enhancing level, anxiety becomes less bothersome.

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

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

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

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

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

“You get a feeling of irritability and restlessness to begin with, as it has a slight 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 around 60% of people see benefits after three months, compared to 40% after one month.


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

The message is, if you can, try to stick to it. “Have a loved one watch you closely for the first few weeks,” says Dr. Cannon.

And if not, try something else. In 2008, experts at the University of Pittsburgh found that 40% of a group of 334 depressed patients saw their mental health improve after switching SSRIs.

But doctors say these drugs are not the ultimate solution. There are classes of drugs that work on different brain chemicals to improve mood and relieve anxiety.

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

A 2018 review by researchers at the University of Oxford compared clinical trial dropout rates – the percentage of patients who stopped taking a treatment before the end of the study – and the effectiveness of 21 different antidepressants.

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

I have now been on Prozac for six months, which is around the time the doctors suggest stopping them if you feel better. And while I feel a lot less bothered, with a tough year ahead, I’d rather not risk letting my brain marinate in its natural juices.

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

Leave a Comment