Scientists at Harvard Medical School in Boston have uncovered important clues about what may cause schizophrenia. First signs of the disorder often appear in adolescence, and the team thinks they may have found the reason why. According to a study published this week in Nature, schizophrenia may be the result of overactive "brain pruning" caused by high levels of a molecule called complement component 4 (C4).

New Scientist explains that C4 is primarily known for the role it plays in immune system processes. In the blood, the molecule binds to unwanted microbes, signaling to immune cells that they should be destroyed. However, scientists found that C4 also plays a role in the brain, binding to synapses, which connect neurons, and signaling that they should be consumed by immune cells.

While all teenagers go through a process known as brain pruning, in which they lose synapses, scientists now believe that too many C4 molecules may cause too much pruning. According to New Scientist, postmortem studies have found that people with schizophrenia have fewer synapses than their peers. Harvard molecular biologist Steven McCarroll believes that risky C4 gene variants are responsible for over-pruning. “[The study] suggests that schizophrenia can result from a normal stage of teenage brain maturation gone wrong,” explains New Scientist.

Of course, schizophrenia is an incredibly complex condition, and it’s more than likely that other factors play a role in its onset as well. But the finding is a major breakthrough in the study of schizophrenia, linking the condition with immune system processes and presenting very promising future avenues of study.

[h/t: New Scientist]