Australian National University researchers discover swelling of part of the brain in people with both depression and anxiety

Our understanding of the relationship between the brain and mental illness has grown, with a new study into those who suffer from both depression and anxiety.

The research, conducted at the Australian National University, looked at more than 10,000 people with both disorders and discovered that part of their brain, the amygdala, swells in size.

Now published in The Journal of Psychiatry and Neuroscience, the findings could offer hope for sufferers by shedding light on their combined impact on the brain.

Key points:

• Researchers examined 10,000 people with both depression and anxiety
• While depression shrinks the hippocampus, researchers found the coexistence of anxiety swelled the amygdala
• A clinical researcher says the new findings could offer hope to sufferers

A step forward in understanding the brain

Scientists had already established that those with depression often experienced a shrinking of the part of their brain linked to memory and learning, the hippocampus.

By choosing to look at those with anxiety as well, this study has cornered a new area of research by seeing how it impacted the area of the brain linked with emotion, lead researcher Daniela Espinoza Oyarce said.

“Many studies looking at the effect of depression on the brain do not account for the fact that people who have depression often experience anxiety too,” Ms Espinoza Oyarce said.

“We found people who have depression alone have lower brain volumes in many areas of the brain, and in particular the hippocampus.

But those with both mental illnesses did not experience that shrinkage, she said, with anxiety lowering the effects on brain volume size by three per cent.

She said this indicated that the true effect of depression had been underestimated, while also revealing the brain’s reaction to anxiety.

“That is why it ends up being larger — that is what we think the process is.”

What does this mean for sufferers?

For many people living with mental illness, the process of finding a medication or therapy that offers relief can be long.

Ms Espinoza Oyarce said the evidence that those with both conditions did not experience changes to their hippocampus was not necessarily good news.

“What depression does to the brain, is that many areas are affected — but when depression is together with anxiety, anxiety masks the effects,” she said.

“We don’t know why that is happening, or exactly how.”

She said the hope was that with this new information, clinicians would be able to land on the appropriate medication for an individual more quickly, knowing how differently their brain might be reacting if they had just one condition or both.

She said the findings further highlighted how much of a role our brains played in our moods.

“We tend to think that when we are feeling a bit down or when we are anxious, everything is in our heads, but it can be traced back to certain areas of the brain.”

‘An overdue focus’ in mental health research

Up to 50 per cent of people who have depression also have anxiety, Dr Genevieve Rayner, a research fellow in Clinical Neuropsychology at the Melbourne School of Psychological Sciences, said.

She said research had often excluded anxiety from studies into depression because it was considered “a complicating factor”.

“When actually that’s the reality for a lot of people with depression is that they also suffer from anxiety at the same time,” she said.

The new findings on the effects of both conditions were “an overdue focus”, she said.

“To understand what the influence of that anxiety is on the structures of the brain is really important,” she said.