It is the most widely used anti-depressant in history, has entered into our cultural lexicon and was perhaps the only pharmaceutical to ever become "trendy". But on the 25th anniversary of the introduction of Prozac, the "happy pill" remains controversial.

It has been taken by more than 40 million people around the world and has made billions for the Eli Lilly Company behind it. With anti-depressant use at an all-time high in Ireland (and the developed world), there are passionate arguments on both sides of the Prozac debate – from those who see it as a necessary and vital treatment to those who believe the drug is merely a triumph of marketing and no substitute for "talking cures"/cognitive-behavioural approaches to depression.

When launched in 1988, Prozac immediately captured the public imagination. The marketing team behind the launch said “We created the name ‘Prozac’ – intentionally distancing it from everything typically associated with anti-depressants: strong chemicals, side effects and mood swings.”

Modern drug
Perceived as a good, clean, modern drug, Prozac caught fire. A best-selling book, Prozac Nation , helped popularise the drug's appeal and there were claims that here at last was a drug that could save jobs, marriages and lives.

Glowing testimonials during the first few years of the drug's availability coupled with a media-friendly appeal, seemed to have ushered in a new era of talking about and dealing with depressive disorders. And new vistas were being explored: the BBC arts review programme, The Late Show , explored the effects of Prozac on creativity with New Order's Bernard Sumner saying using the drug put him in a better place and helped him through a period of "writer's block". Prozac was becoming "chic" and viewed as a lifestyle accessory.

The bar was being lowered on depression. Even the mildest ailment was now having Prozac thrown at it and some felt that this new “modern depression” was merely a creation of Prozac’s marketing department.

But the drug's critics were lining up. David Healy, a professor of psychiatry at Cardiff University and the author of Pharmageddon , told a recent BBC documentary that: "What made Prozac good was not that it was potent, which it really was not, but that it had really good marketing. The drug made us overcome the natural caution most of us have about pills and convinced us that we absolutely had to have these things."

As a “one-stop shop” treatment, Prozac has been accused of damaging therapeutic alternatives.

In the modern era, people want a quick fix of “happiness”, not some long, drawn-out therapeutic “talking cure”. There has recently been controversy over Prozac being prescribed for people who have experienced bereavement and want a pill to take the “sadness” away.

Ridiculous expectation
With dim-witted celebrities talking about how the drug made them "happy", there is almost the ridiculous expectation now that your general sense of wellbeing can be enhanced by taking the drug.

The irony here is that no one really knows exactly how Prozac works.

There is the idea that the drug raises levels of feel-good “serotonins” but the scientific data is complicated. For every one medical practitioner who lauds the drugs, it seems there is another who believes it is dangerously addictive and over-prescribed.

However, Prozac is a vitally important drug – not so much in its pharmaceutical make-up or its purported efficacy, but in how it has opened up a public debate about happiness/depression and “cures”.

Pre-Prozac, the diagnosis and treatment of depression was a taboo subject for many – dominated by frightening images of electro-convulsive therapy.

The sheer ubiquity of the drug – and the scale of the debate around it – has presaged a new era of insight into and analysis.

If Prozac doesn’t live up to its billing as “bottled happiness” as many claim, a broader view is now being taken of what works and how.

If holistic medicine was the greatest casualty of widespread Prozac use, has that much-maligned treatment area a place in a Prozac-sceptical world?

What is clear with the continuing debate about the role of pharmaceuticals in the treatment and management of depression is that herbal remedies (once blown out of the water by Prozac) are staging a comeback.

Doctors and public alike have more confidence in remedies such as St John’s Wort and not just for ethical, medical and psychological reasons. Even the placebo effect of taking a remedy can help people. The very stimulation of one’s own powers of self-healing can have a potent effect.

Twenty five years into Prozac and it can appear we are no wiser to the drug. But from the initial evangelical fervour to the now more robust scepticism about the drug, we have travelled a great way.

If any consensus can be reached it is that Prozac has as many fans as it has enemies.

There remain those in the medical/psychiatric establishment who believe it to be a life-saver and those who are vehemently opposed to its continuing usage.

Hollywood does Prozac
One of this year's biggest films – Stephen Soderbergh's Side Effects – is about the ramifications of a young woman being prescribed anti-depressants. The "Hollywood does Prozac" theme of the film has been picked over by the medical world, giving fresh impetus to a debate that is still throwing up new hopes and new directions. We may not have arrived at our "Post-Prozac Nation" but we're getting there.