The Scottish Association for Mental Health says reliable research has only been conducted for a six-to-10 week period and many of their members are experiencing serious side-effects and withdrawal symptoms.

But this is disputed by Prozac's makers, who insist the drug - when taken correctly - is totally safe.

Selective Serotonin Re-uptake Inhibitors (SSRI's) were launched in the 1980s as the non-addictive alternative to Valium.

Since then, it has been approved and marketed in more than 90 countries and is said to be prescribed to more than 40 million people.

Prescription of SSRI's has risen five-fold in the past 10 years but the association says increasing numbers of patients are experiencing adverse symptoms.

It also believes that existing studies on the long-term effects of taking SSRI's cannot be relied upon.

Clinical studies

But Prozac's makers, Eli Lilley, say on their website: "For more than 14 years, the safety and effectiveness of Prozac continue to be demonstrated worldwide through scores of clinical studies and patient success stories.

"The safety and effectiveness of Prozac have been thoroughly studied in clinical trials with more than 11,000 patients.

"There have been more than 3,500 publications on Prozac in medical/scientific journals."

However, tests using Lustral, a very similar medicine, suggests that the Prozac "family" of drugs, known as SSRIs, may have dangerous side-effects.

There have long been concerns that the drug is prescribed to patients who suffer only mild symptoms of depression, and who are not clinically ill.

Research carried out two years ago by the North Wales Department of Psychological Medicine found that two out of 20 healthy volunteers on Lustral became dangerously suicidal.

Within the past year GlaxoSmithKline, which makes Seroxat, has changed the labelling on its product to warn patients that they can experience withdrawal effects if they come off it too quickly.