​London, June 9 (IANS) Most of the commonly prescribed antidepressant drugs are ineffective and some may be unsafe for children and teenagers with major depression, according to a study.

"The balance of risks and benefits of antidepressants for the treatment of major depression does not seem to offer a clear advantage in children and teenagers, with probably only the exception of fluoxetine," said co-author Peng Xie from the Chongqing Medical University in China. 

Major depressive disorder is common in children and adolescents across the world, affecting around 3 per cent of children aged 6 to 12 years and about 6 per cent of teenagers aged 13 to 18 years.

"Without access to individual-level data it is difficult to get accurate effect estimates and we can't be completely confident about the accuracy of the information contained in published and unpublished trials," said study lead author Andrea Cipriani from the University of Oxford. 

Cipriani and colleagues did a systematic review and network meta-analysis of all published and unpublished randomised trials comparing the effects of 14 antidepressants in young people with major depression up to the end of May 2015, according to the study published in the journal The Lancet.

Analysis of 34 trials involving 5,260 participants (average age 9 to 18 years) showed that the benefits outweighed the risks in terms of efficacy and tolerability only for fluoxetine.

Nortriptyline was less efficacious than seven other antidepressants and placebo.

Imipramine, venlafaxine, and duloxetine had the worst profile of tolerability, leading to significantly more discontinuation than placebo. Venlafaxine was linked with an increased risk of engaging in suicidal thoughts or attempts compared with placebo and five other antidepressants. 

The researchers warned that due to the lack of reliable data, it was not possible to comprehensively assess the risk of suicidality for all drugs.

"Hundreds of thousands of people worldwide have agreed to participate in trials aiming to find better treatments for their disorders and, ultimately, help the progress of medical science," Cipriani said.

"Patients' privacy must be guaranteed by adequate policies and technological measures, but delay in implementing responsible data sharing policies has negative consequences for medical research and patient outcomes, as demonstrated by this study," he added.​