Levels of evidence are proposed hierarchies of research types that intend to rank the strength and reliability of research findings based on study design. However, the idea that research can be ranked ...

After decades of study, there remains no clear evidence that serotonin levels or serotonin activity are responsible for depression, according to a major review of prior research. After decades of ...

After decades of study, there remains no clear evidence that serotonin levels or serotonin activity are responsible for depression, according to a major review of prior research led by UCL scientists.