Doctors have been issued with new guidance on the prescribing of antidepressants.
Prozac is included in the new guidelines
The National Institute for Clinical Excellence called on doctors to exercise more caution in prescribing the drugs.
Separate advice from the Medicines and Healthcare Products Regulatory Authority demanded stronger warnings on drugs such as Prozac and Seroxat.
It says advice on potential withdrawal symptoms should be reinforced.
One woman in 15 and one man in 30 are affected by depression each year.
And around 44 adults in every thousand are estimated to have an anxiety disorder.
The NICE guidelines say no type of antidepressant should be used in the initial treatment of mild depression.
But for patients with moderate to severe depression who are deemed to need antidepressants, drugs such as Prozac and Seroxat should be favoured above other types because they are less likely to be discontinued due to side-effects.
Both belong to a family of drugs known as Selective Serotonin Reuptake Inhibitors (SSRIs).
In 1997, around 6.5m prescriptions were written for SSRIs. By 2002, this had risen to 13.3m.
They have become increasingly popular over the last decade, as doctors considered them safer than the older tricyclic drugs which carried a high risk of overdose.
The NICE guidelines say all patients prescribed any antidepressant must be warned of possible side-effects when they stop taking the drugs, or reduce their dose.
For those patients with anxiety disorders, NICE recommends therapy, such as counselling or cognitive behavioural therapy (CBT), are the ideal treatment, with SSRIs as second-choice.
Andrew Dillon, Chief Executive of NICE, said: "These guidelines recognise that whilst medication has an important role to play in treating these conditions, there are also many effective alternatives."
The MHRA said the analysis of both published and unpublished data by experts on the Committee on Safety of Medicines (CSM) showed "a modest increase in the risk of suicide from SSRIs compared to placebos [dummy pills]" in adults.
But it added that there was good evidence that there was "no clear increase" in the risk of suicide associated with SSRIs compared to other antidepressants.
Antidepressants should not first choice for mild depression
People with moderate to severe depression who require antidepressants should be given SSRIs (such as Seroxat and Prozac)
Anxiety disorders should initially be treated with therapy
Stronger warning of withdrawal symptom risk on SSRIs
The lowest dose possible should be prescribed
However, the MHRA said there should be offered greater monitoring as a precaution - particularly younger adults (aged 18 to 30) taking SSRIs.
Last year, it advised no SSRIs, except Prozac, should be given to under 18s after concerns the drugs were linked to suicidal thoughts in some patients.
The MHRA has also called for the lowest recommended dose to be prescribed in the majority of cases.
But people who are on SSRIs are advised not to stop taking them, or reduce their dose, without speaking to their GP.
Professor Kent Woods, Chief Executive of the MHRA, said: "The benefits of SSRIs in adults are still considered to outweigh the risk of adverse drug reactions."
Professor Louis Appleby, National Director for Mental Health, welcomed both sets of guidance.
Graham Archard, vice chair of the Royal College of GPs, said: "We welcome this guidance but GPs face a difficult dilemma when treating depression. With a chronic shortage of counselling and psychotherapy available on the NHS, GPs often feel they have little choice but to prescribe anti-depressants in mild to moderate cases.
"We urgently need more resources in place so patients can be referred for non-drug therapies."
Paul Farmer, of the mental health charity Rethink said antidepressants could give people space to tackle the issues underlying their condition, but were "not a cure".
"People should instead have access to psychological treatments and support underlying issues that lead to the anxiety," he said.
But Marjorie Wallace, Chief Executive of the mental health charity Sane, added: "Unfortunately, trained and experienced therapists are currently like gold dust and those needing therapy may have to wait many months."
A spokesman for GlaxoSmithKline, which makes the biggest-selling SSRI, Seroxat, said the new guidance clarified the use of such drugs, and added they had revolutionised the treatment of depression.