Major depressive disorder (MDD), on top of being the most prevalent mood disorder, is also considered to be one of the most burdensome diseases. This underscores the worthiness of examining recent trends in MDD clinical trials and analyse the effects of the Covid-19 pandemic on MDD research.

From 2016 to 2021, the US ranked as the top host of MDD clinical trials with 30% of such studies recruiting from the country in five out of the past six years. China is second place in this ranking, hosting 14% of MDD clinical trials.

Notably, China hosted the most MDD trial initiations in 2020. With sponsors running trials in China experiencing the first signs of clinical trial operations interruption due to the pandemic, these sponsors would also be the first to implement any mitigation strategies to keep MDD clinical trials running compared to other markets. These strategies may have allowed China-based trials to be more equipped in conducting studies in the first year of the pandemic.

Iran holds third place with 11% of studies, followed by India and Canada which both hold 5% of studies. Notably, no European countries are included in the top five research locations for MDD studies. European countries generally conduct the highest proportion of multinational trials relative to all other regions irrespective of indication. And MDD studies are largely single-country studies (92%), therefore a lower number of European studies may be expected overall.

Who are sponsoring major depressive disorder trials?

Observing the pattern of sponsorship, most of the research is conducted by non-industry sponsors (61%) relative to industry sponsors (39%). The pattern of sponsorship may be attributed to the MDD research space being fairly-well established, with a variety of medications already on the market. Furthermore, current drug development systems allow institutions to begin identifying promising candidates that could be developed into commercial products by company sponsors that attain the commercial rights later in the development process.    

Since 2016, the level of research directed towards MDD has shown an upward trend, with the longest constitutive growth period occurring in 2017–2019. A total of 19% of initiated trials occurred in 2019, followed by a record drop in 2020, likely due to the disruptive effects of the pandemic.

There was a record increase in trial initiations from 2020 to 2021, with 2021 showcasing the highest number of trial initiations (20.7%) over the five-year period. In 2021, there was also a record use of virtual trials (29.5%).

Are there major depressive disorder biomarkers?

Due to gaps in our understanding of the etiology of MDD, there is no definitive biomarker that can be used to diagnose MDD. The current standard utilises the Hamilton Depression Rating Scale, a questionnaire utilised to guide diagnosis and evaluate recovery.

Therefore, MDD study design regarding diagnosis and treatment evaluation can be transferred to a decentralised virtual model with little difficulty compared to other indications. In 2021, an increased usage of decentralised virtual trials translated to an increased number of overall studies as the decentralised approach vastly increased participant outreach, allowing for a greater number of participants in clinical studies.

Increasing trend of virtual trials in major depressive disorder
Distribution of total MDD clinical trials by year and proportion of virtual trials, 2016-2021

In addition, as physical biomarkers are largely ineffective for MDD studies, we can expect this decentralisation trend to continue as this study design can allow for the determination of the necessary outcome measures in the majority of MDD studies. In 2021, the benefits of decentralisation within the MDD research space were showcased, allowing for a significantly greater research output that could lead to further advancements in the field in the years to come.