The risk of suicide attempts does not increase when people start taking anti-depressants, a US study suggests.
Those studied took a range of antidepressants
The conclusion, in an American Journal of Psychiatry study, challenges concerns about the drugs' effects.
The team from Seattle's Group Health Co-operative looked at 65,000 people who were prescribed the drugs.
They say unnecessary concerns over the drugs may mean people with depression are not taking drugs which could benefit them.
The researchers claim this is the first published analysis to compare the risk of suicide attempts before treatment with the risks following treatment.
They looked at medical and pharmacy records for the patients, who collected prescriptions for antidepressants from 1992 to 2003.
Deaths by suicide were determined from death certificates and suicide attempts were identified from hospital discharge data.
Because the organisation has computerised data for its patients, it was also able to look at suicidal behaviour in the months before they were prescribed the drugs.
There were 76 suicide attempts in that period, compared with 73 in the three months before the prescription being issued.
The highest risk of an attempt was in the month before the drug was given.
There were 31 deaths from suicide in the six months following the antidepressant prescription, with no initial peak in the rate.
And adolescents were significantly more likely to attempt suicide than adults in their first six months of taking the drugs.
The study also found that newer antidepressants - SSRIs, or Selective Serotonin Re-uptake Inhibitors, which include commonly prescribed drugs such as Prozac and Seroxat - were associated with a faster decline in rates of suicidal behaviour than older drugs.
As with adults, the rate was highest in the month before treatment and declined by about 60% after treatment began.
Dr Greg Simon, who led the research, said: "Our findings show that, fortunately, suicide attempts and death by suicide are rare following the initiation of antidepressants.
"The period right after people start taking antidepressant medication is not a period of increased risk. In fact, risk after starting medication is lower than before."
He said recent concerns over the possible impact of antidepressants may mean people mistakenly believe suicidal behaviour is common after taking antidepressant medications.
He added: "There may be subgroups of people who become more agitated or suicidal after taking these drugs, and those people should seek help from a doctor or therapist right away if that happens.
"But our study showed that on average, the risk of suicide actually goes down after people start taking the antidepressant."
However, he agreed people who have just begun taking the drugs need careful monitoring, but to ensure they are getting the right dose - rather than because he drugs are especially dangerous.
Margery Wallace of the mental health group Sane said: "We know and accept there are concerns for some.
"But these should not deprive the majority. This research is helpful in giving a perspective."
However, Dr Robert Temple, Food and Drug Administration Medical Policy Director of the Center for Drug Evaluation and Research, writing in the FDA's 'Pink Sheet' said: "The new study bears only a tangential relationship at best to the previous information.
"The new study doesn't have an untreated group. They have no information at all about what would have happened to those people had they not been treated.
The UK's Committee on Safety of Medicines, which has considered the safety of SSRIs, concluded there may be an increased risk of suicidal behaviour with any antidepressant, and anyone prescribed the drugs should be closely monitored.