Depression is one of the most common mental illnesses, and for more than half a century it has been linked to disruptions in the serotonin neurotransmitter system. However, the evidence to support that link has been indirect, leading researchers in the field to request a reexamination of the “serotonin hypothesis.” Only about half of patients respond to antidepressants, and less than 30% see total remission. According to a recent SciTechDaily article, a new study, published in the journal Biological Psychiatry, has finally made a direct link.
The study, which included researchers from Imperial College London, King’s College London, Copenhagen University, and the University of Oxford, used novel imaging to examine the magnitude of serotonin released from neurons in response to a pharmacological challenge. The study found no link between the severity of depression and the extent of serotonin release capacity deficits. Because depression is a multifaceted disorder that can have a variety of causes, the subtypes can include multiple neurotransmitter systems, not just serotonergic dysfunction. But the study did show that serotonergic deficits are present in depressed, unmedicated people.