Schizophrenia is a severely debilitating mental illness that affects around one in 100 individuals in both the United Kingdom and the United States. “Schizophrenia” is actually an umbrella term for a complex range of different neurological disorders, each with a host of symptoms that can sometimes be difficult to detect during the earlier stages of the affliction. Fortunately, a new study, published in the American Journal of Psychiatry, has revealed that a type of immune cell is more active in the brains of people at risk of schizophrenia. This should aid medical doctors in the early detection of the disorder.
This new study, led by the Medical Research Council (MRC) Clinical Sciences Centre at Imperial College London, used brain scans to track a type of immune cell called microglia, which respond to damage and infection by facilitating inflammation. These cells also initiate and control a neurological process named “synaptic pruning,” wherein the connections between brain cells are rearranged to improve the overall electrochemical connections within the brain. Think of it like trimming a house plant: some connections are removed in order to allow others to strengthen.
Microglia have been previously linked to Alzheimer’s, depression and schizophrenia, with one theory suggesting that errors in how synaptic pruning is carried out leads to disordered, weak connections and, consequently, these types of neurological disorders.
Diagnosis of schizophrenia is difficult, so much so that there are two categories of symptoms. Some are “positive” – the symptoms like hallucinations and delusions that are only found with those suffering from the disorder. Others are “negative” – symptoms that represent more subtle changes in a person’s behavior, such as a lack of emotional responsiveness. The negative symptoms often appear many years before the onset of any positive symptoms, but in many cases the negative symptoms are indicative of another mental disorder.
The researchers took a sample of 56 people to examine with a positron emission tomography (PET) scan. Of these, 14 were considered to have a high-risk of anxiety, exhibiting a range of negative symptoms and some positive symptoms, such as delusional thoughts. Another 14 had been diagnosed with schizophrenia, all of whom were showing strong positive symptoms. The rest were neurologically healthy individuals, and acted as the study’s control.
The researchers found that the more active the microglia were, the more severe symptoms of schizophrenia they had. This is the first time the inflammation in the brain can be directly tracked to the development of the disorder; the fact that these cells showed activity during the earlier stages of schizophrenia was particularly revelatory.
Dr Oliver Howes, head of the psychiatric imaging group at the MRC Clinical Sciences Centre, said in a statement: “This is a promising study as it suggests that inflammation may lead to schizophrenia and other psychotic disorders. We now aim to test whether anti-inflammatory treatments can target these.”
Depression made the headlines earlier this year when it was likened to an allergic reaction of sorts. Indeed, a growing number of studies are suggesting that depression might be a side effect of the body’s immune system responding to a microbial aggressor. Proteins called cytokines, upon sensing danger, initiate inflammation in the body, switching the brain into “sickness defense” mode. Inflammation is known to dramatically occur during depressive episodes, which suggests two things: that depression could be caused by an immune system response, and that it could also be treated with anti-inflammatory medicine, potentially like schizophrenia.