November 3, 2018
New Study Finds Three New 'Subtypes' Of Depression -- And One Is Resistant To Medication

A new study is showing that there are different "subtypes" of depression, Medical News Today is reporting. By learning more about these subtypes, scientists are hoping to discover new forms of treatment that can cater to a person's specific subtype -- especially since one subtype is believed to be immue to selective serotonin reuptake inhibitors (SSRIs), the most common medication prescribed to people suffering from depression.

It's been estimated that over 300 million people around the world have depression, and at least 16 million of these people live in the United States. Sixty percent of that U.S. population find that their depression severely impairs them in some way, and 30 percent of people with depression don't feel like the treatments they've been given are working. SSRIs for example, are supposed to increase levels of serotonin, aka the "happy hormone," in the brain. New research conducted by a team led by Professor Kenji Doya, of the Neural Computation Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) in Japan, shows we're coming closer to finding out why SSRIs work for some and not for others.

"It has always been speculated that different types of depression exist, and they influence the effectiveness of the drug," Doya explained. "But there has been no consensus."

Doctor handing out prescription

The researchers decided that they would gather the data they needed from examining 134 participants, half of whom were clinically diagnosed with depression. The researchers analyzed questionnaires and blood tests. They also analyzed information about the participants' life histories, mental health, sleep patterns, and other potential causes of stress in their lives.

Each participant received an MRI scan so scientists could monitor their brain activity and examine how the connections between their brain regions were working. From this information, they were able to group together measurable features like "incidence of childhood trauma" and "initial severity of the depressive episode." From these measurable features, they were able to form five data clusters. And from there, they found the three subtypes.

One of these subtypes, however, was different from the other two. It was not likely to respond to medication. This subtype was also different because it correlated with high functional connectivity as well as with childhood trauma, while the other two did not. The researchers came to the conclusion that childhood trauma could play a big part in why a depressed brain doesn't respond to treatment. These findings could lead to the creation of more treatments that are more targeted to the unresponsive subtype.

"It provides scientists studying neurobiological aspects of depression a promising direction in which to pursue their research," said Doya.