The risk is so great that America's drug regulator, the Food and Drug Administration (FDA), has told drug manufacturers to strengthen the warning about suicidal tendencies, especially among patients aged between 18 and 24 years.
The risk is highest during the 'initial period', which is generally considered to be within the first four to eight weeks. This view of the initial period goes back to the 1950s, when the first generation of antidepressants came to the fore - and this is where doctors have got it so wrong.
It's always been believed that antidepressants have a "delay in onset of effect", as drug companies put it, which means that they don't start working right away.
But this just isn't true. A 2005 meta-analysis of 76 different trials found that 60 per cent of patients reported an improvement in the first two weeks after starting antidepressant therapy.
A study last year, which looked only at SSRIs (selective serotonin reuptake inhibitors), a special type of antidepressant, found that all the beneficial effects happened in the first week of treatment, if they were going to happen at all.
(Source: British Medical Journal, 2007; 334: 911).
E-news broadcast 10 May 2007 No.358 [Subscribe]