Anyone who’s dealt with depression can tell you that rumination — the kind of repetitive, obsessive, and uncontrolled stress-driven thinking about whatever is bothering you without necessarily coming up with a solution to it — is one of the most difficult symptoms to treat.

Luckily, researchers are gaining more clues about what’s going on in the brain that may underlie the tendency to ruminate. The runaway negative thoughts can actually be both symptoms of depression and a precursor to it.

Adolescence is a time when the brain is undergoing enormous change — it can also be an especially difficult time for many teenagers socially, and this can trigger depression. And with young people, as with people of any age, it’s particularly helpful to catch the signs early, to prevent them from turning into full-blown depression.

Depression is something that can just happen to someone given certain circumstances — genetic predisposition, life stress, or a traumatic event at any stage in life. It’s not a life sentence.

The researchers of the current study wanted to find out if the brains of depressed young people looked different from those of healthy people in how certain brain areas are connected to one another.

With MRI technology, they scanned the brains of 30 unmedicated participants (ages 18-23) who had never been medicated for their depression, along with 23 health individuals who served as controls. The participants’ brains were scanned while they weren’t doing anything in particular aside from just being in an awake, "resting state."

The brains of the depressed people did appear to have different patterns of connectivity: Some areas were hyper-connected — that is, they were communicating with each other too much. Importantly, these were areas that are known to be involved in rumination.

“Rumination is not a very healthy way of processing emotion,” said study author Scott Langenecker in a news release. “Rumination is a risk factor for depression and for reoccurrence of depression if you've had it in the past.”

Cognitive control — being able to shift one’s own thought processes — and rumination are inversely related: As rumination goes up, cognitive control goes down, and vice versa.

The brain, particularly in adolescents and young adults, is very plastic, or capable of being “rewired,” given the right forms of treatment.

“We think that depression is a developmental outcome, and it's not a foregone conclusion that people need to become depressed,” said Langenecker. “If we can provide prevention and treatment to those people that are most at risk, we might be able to prevent depression, reduce the number of depressive episodes, or reduce their severity.”

Depression is something that can just happen to someone given certain circumstances — genetic predisposition, early life stress, or a traumatic event at any stage in life. It’s not a life sentence. Early intervention is especially important for young people, since their brains are still developing. But even if early symptoms like rumination do turn into depression, it’s still treatable with the right therapy.

The research was carried out at the University of Illinois at Chicago and is published in the journal PLOS ONE.