Antidepressants may be associated with an increased risk of suicidal behaviour, particularly in the early stages of treatment, the results of three new studies indicate.

The studies, which looked at SSRIs (selective serotonin reuptake inhibitors) – the most commonly prescribed class of antidepressant – as well as tricyclic antidepressants, are published in the latest edition of the British Medical Journal.

For the first study, a team of researchers analysed 702 trials involving over 87,000 patients with depression, to establish whether the use of SSRIs was linked to suicide attempts.

That study found that patients taking SSRIs were twice as likely to attempt suicide, compared with patients who were taking a placebo.

However when fatal suicides only were taken into account, i.e. where a person had succeeded in taking their own life, SSRIs did not appear to increase the risk. The researchers said that while the absolute risk of suicide is low, the widespread use of SSRIs makes this a ‘population health concern’.

The second study looked at 477 trials that had been submitted by drug companies to a safety review by the British Medicines and Healthcare products Regulatory Agency (MHRA). These trial compared the effects of SSRIs with placebos in adults with depression and other clinical conditions.

The researchers found no evidence that SSRIs increase the risk of suicide. However they found weak evidence of an increased risk of self harm. They warned that overall, increased risks of suicide and self harm caused by SSRIs cannot be ruled out. They recommended that patients should be warned of the potential hazard and monitored closely in the early weeks of treatment.

The third study was based on information from the British GP research database. It looked at the risk of self harm and suicide in more than 146,000 patients taking SSRIs and tricyclic antidepressants for the first time.

That study found that the risks of self harm and suicide were no different in patients taking SSRIs, compared with those taking tricyclic antidepressants. However those aged under 18 who were taking SSRIs seemed to be at an increased risk of self harm.

According to an accompanying editorial in the BMJ, these studies should provide some useful insights for clinical practice. For instance, they should make doctors aware that SSRIs and tricyclic antidepressants may induce or worsen suicidal behaviour during the early phases of treatment, therefore patients should be monitored closely.

The results should also discourage the prescribing of antidepressants to children and adolescents.

“The debate is not yet done but these papers crystallise arguments that have been drifting in the ether these past months. How many people who turned to ‘happy pills’ would not have done so if they had been fully aware of the potential harms?”, said BMJ acting editor, Kamran Abbasi.

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