An overactive immune system may be a key factor in the development of schizophrenia, according to a new study by the UK Medical Research Council. The study confirmed previous findings that microglia, cells responsible for the main form of immune defense in the brain, activity is elevated in the brains of patients with schizophrenia.

The study suggests that inflammatory processes play an important role in the development of the disease, and researchers hope to test anti-inflammatory drugs to treat, or hopefully prevent the disease.

Schizophrenia, a severe mental illness characterized by auditory and visual hallucinations, delusions, and psychotic episodes, affects around 1 percent of Americans. The disease’s cause is still unknown, but past studies have implicated elevated inflammatory processes as a potential factor. The research team hoped to identify how the activity of microglial cells is associated with schizophrenia, and if it is altered in even the early stages of the disorder.

A type of brain imaging technique using a chemical dye allowed researchers to observe the levels of microglia activity of 56 people — 14 patients diagnosed with schizophrenia, 14 who were at risk for developing the disease, and 28 healthy individuals as controls. The highest level of activity was detected in the brains of patients with the condition, but those at risk for developing schizophrenia also showed heightened activity levels.

“This is a real step forward in understanding,” Dr. Olvier Howes, the head of the psychiatric imaging group at the MRC Clinical Sciences Centre, told BBC News. “For the first time we have evidence that there is over-activity even before full onset of the illness.”

Howes explained that if we could reduce this activity prior to the onset of full-blown schizophrenia, we might be able to prevent the illness. He likened the microglia to an overenthusiastic gardener — shearing away not only that which is bad for the brain, but severing connections that leave it incorrectly wired.

“You can see how that would lead to patients making unusual connections between what is happening around them or mistaking thoughts as voices outside their head and causing the symptoms we see in the illness,” he said.

Further studies are now necessary to determine if and how an anti-inflammatory drug could be used to prevent schizophrenia. Some trials have already shown that anti-inflammatories may help patients when administered alongside traditional medication, but the trials were too small to draw large scale conclusions from. Howes advised patients to discuss all decisions about medication with their doctor, and not to self-prescribe.

Source: Bloomfield P, Selvaraj S, Veronese M, Rizzo G, Bertoldo A, Howes O, et al. Microglial activity in people at Ultra High Risk of Psychosis and in Schizophrenia: An [11C] PBR28 PET Brain Imaging Study. The American Journal of Psychiatry. 2015.