Major depressive disorder (MDD) is the most predominant mood disorder worldwide. Depression places a huge burden on the individuals affected and on society as a whole. Evidence suggests that more and more of us are seeking treatment for depression, with the NHS reporting that antidepressant prescriptions reached an all time high in 2017. Drugs with “antidepressant” properties were first identified in the 1950s, when clinicians were surprised to learn that an anti-tuberculosis drug named iproniazid induced feelings of euphoria in their patients. Since then, a vast array of pharmacological treatments have been developed to treat the disorder by targeting a number of different pathways. The question is – do they actually work?
Given their wide use, it may come as a surprise that the efficacy of antidepressants has been hotly debated within the scientific community; and by efficacy I don’t mean which one is most effective at treating depression (although there’s plenty of debate about that too), I mean whether or not they reduce depressive symptoms at all. Studies examining the effectiveness of antidepressants have often been conflicted, with some reporting stark improvements, and some reports of antidepressants performing similarly to placebo sugar pills. Concerns have also been raised by many about the validity of clinical trials funded by the pharmaceutical companies who undoubtedly have much to gain if a new drug treatment is shown to be successful; could this potential conflict of interest bias the findings in favour of the drug treatments?
A landmark new study published in The Lancet systematically examined the evidence from 522 randomised controlled trials of commonly prescribed antidepressants and combined the evidence to reach a conclusion. The verdict? Resoundingly positive.
All antidepressants, even the least effective, outperformed placebo controls. On top of that, the authors also reassured that although 78% of studies were industry funded, this was not associated with a difference in drug responses. The antidepressant amitriptyline was found to be the most effective, but it’s important to take into account that the analysis relies on the average efficacy of each drug in a treatment group of patients compared to a control group. Therefore, a drug may be the best choice for one group of patients, but not for another. Given that all antidepressants have some therapeutic benefits, this may encourage more exploration by clinicians to find the best treatment for individual patients.
One group of patients remain left behind. The study excluded patients with treatment resistant depression (TRD); a clinical subgroup who do not respond to multiple courses of antidepressant treatment. Little is understood about what differentiates a person suffering from depression who gets better with treatment, and a person who does not. Now that we know antidepressants work, at least for some people, it’s become even more important to tease apart the subtypes of MDD, determine which treatment is best in which case, and develop further treatments to give all patients the best chance of recovery.
This article was written by Kaitlyn Hair and edited by James Hitchen.