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

By Eve Simmons, Associate Health Editor, The Mail On Sunday

Updated: 9:27 a.m. March 19, 2023

In the six years I’ve worked at The Mail on Sunday, I’ve recovered from an eating disorder, suffered several severe anxiety attacks, moved house twice and got married. Now I’m getting divorced.

Still, I hadn’t taken a single day off for mental health reasons until late last year – and it had nothing to do with this.

In fact, my breakdown was due to the pills I was taking to help me cope with the above.

It happened in September, two weeks after I started taking the antidepressant Prozac, also known generically as fluoxetine.

I decided to start medication when my anxiety symptoms—pounding heart, tight chest, knotty stomach—began to interfere with my daily life.

My meltdown was due to the pills I was taking to help me cope with the stress mentioned above, writes Eve Simmons, deputy health editor of the Mail on Sunday.

Like eight million others in the UK, I have suffered from anxiety attacks, on and off, for most of my 31 years, usually triggered by stress. I have been prescribed Prozac – one of the most commonly prescribed anti-depressants – twice before, in my teens and 20s, for anxiety. But this last time, something felt different. Within two weeks of starting treatment, I started to feel… a little desperate.

I was at a friend’s birthday grill. It was a lovely day – warm weather, pots of dip and three kinds of sausages – but I started to feel like someone had lit a fire in my chest, or what it might feel like to be threatened with a gun. My body was stiff, anxious thoughts were raging.

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

Even more alarmingly, I developed a sense of separation – of the body being separate from the mind. I basically thought I was going crazy.

After little sleep, I called my MoS Health colleagues the next morning and admitted for the first time that I was not well.


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

I’m not ashamed to discuss my mental health, but my work has always been a kind of refuge from my troubled mind.

This time I couldn’t do anything – write, read or understand. The information simply did not get through.

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

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

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

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

GP was right. The side effects eased after about a month and the treatment has kept me afloat during a turbulent time in my life. But as a health journalist who has written extensively about the benefits of antidepressants, I was startled.

In November, I received a barrage of criticism when I wrote on these pages that my childhood GP had first prescribed Prozac when I was just 15 to treat severe anxiety. On Twitter, some accused me of distributing powerful drugs to teenagers known for side effects such as suicidal thoughts.

According to the official guidelines, antidepressants may only be prescribed to people under the age of 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 save lives. But has 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 improvements in their overall mental health. About half of patients experience at least one side effect. For 1 in 10, these problems are so severe that they stop using them.

Side effects vary between medications, but most commonly 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 about how long these problems last. The National Institute for Health and Care Excellence (NICE), the UK medicines watchdog, vaguely mentions that the pills should take effect within four weeks, while some side effects “may persist for the duration of treatment”. But GPs I’ve spoken to say they’ve noticed a clear trend.

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

Like eight million others in the UK, I have suffered from anxiety attacks, on and off, for most of my 31 years, usually triggered by stress. I have been prescribed Prozac (pictured) – one of the most commonly prescribed antidepressants – twice before, in my teens and 20s, for anxiety.

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

“But if they stick with 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 of some SSRIs has a side effect on other compounds in the brain and elsewhere in the body,” he says.

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

“This can have an effect on the central nervous system, which controls the natural fear response, and could theoretically make anxiety worse. But once serotonin has reached a level that improves mood, anxiety decreases.

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

In a study of more than 600 patients, only 15 percent said serious side effects caused them to stop taking the pill within the first three months, even though 60 percent had severe side effects within 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 seems to be one of the worst offenders.

“I don’t always want to prescribe fluoxetine,” says Dr. Gerada. “You see a lot more anxiety with it compared to other SSRIs.

“At first you get a feeling of irritability and restlessness because it has a mild stimulant effect.”

Several doctors I’ve talked to over the years have told me that patients often find that antidepressants aren’t working because they stop too early. Studies show that about 60 percent of people see benefits after three months, compared to 40 percent after one month.


Some of the less common side effects of SSRIs include flu-like symptoms, toileting problems, and irregular heart rhythms.

The message is, if you can, try to stick with 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 the University of Pittsburgh found that 40 percent of a group of 334 depressed patients improved their mental health after switching SSRIs.

But doctors say these drugs are not the be-all and end-all. There are groups 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 not taking 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 treatment before the end of the study – and efficacy between 21 different antidepressants.

Those that came out on top were strangely 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 have now been on Prozac for six months, which is about the time doctors suggest stopping if you feel better. And even though I feel much less disturbed, facing a challenging year, I don’t want to risk letting my brain marinate in its natural juices.

I know I have the option of wearing them for the next two, three or even five years, but as long as I get out of bed in the morning, I don’t care.

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