More than two million Americans are currently diagnosed with schizophrenia, a serious mental illness that interferes with a person’s ability to think clearly, manage emotions, make decisions, and relate to others.
Mike Hedric, author of the book Connections (The Journey of a Schizophrenic), poignantly describes in the New York Times his own experience with a mental illness that does not allow to distinguish what is real from what is imagined: “Schizophrenia is the devil on your shoulder that keeps whispering in your ear and, no matter what you try, the little demon won’t stop. He hasn’t stopped in the almost nine years I’ve lived with the illness, and he’s not about to stop now. He’s just quieted down a bit. I’d call him my companion but that would imply a degree of friendship, and there’s no way in hell I’m the little devil’s friend.”
Schizophrenia is a chronic brain disorder that affects about one percent of the population. Most commonly, schizophrenia occurs in late adolescence and early adulthood. When schizophrenia is active, symptoms can include delusional thinking, hallucinations, trouble with thinking and concentration, and lack of motivation. Hearing voices (“the devil on your shoulder that keeps whispering in your ear“), or auditory hallucinations as psychiatrists call them, is a common experience for people living with schizophrenia. In fact, it is so common that it is considered to be one of the principal indicators when considering a diagnosis.
When symptoms are treated, most people with schizophrenia greatly improve over time. However, the currently available drugs only control some of its symptoms—they do not act on the underlying causes of the disorder. But what causes schizophrenia? While the causes are unknown, it is known that there is no single cause. Rather, a combination of brain chemistry and genetic and environmental factors are likely to be responsible for the development of this mental illness. Results from a recent study pinpoint some of these possible factors. One of these studies, published in the journal Nature a little more than a month ago, has been touted as a significant advance in understanding the cause of schizophrenia. indeed, the study (Schizophrenia risk from complex variation of complement component 4) provides considerable insight into biological factors related to the immune system that could be involved in the development of psychiatric disorders. Specifically, the study results indicate that the development of schizophrenia is linked to excessive activity of the complement system.
The complement system plays a major role in immunity, leading to killing of infectious microbes and to regulation of inflammation. Thus, it participates in the development of integrated and effective immune responses. The complement system is made up of different proteins, and the scientists found that the gene that codes for one of these proteins, C4, is linked to schizophrenia. This gene, which is composed of two components, C4A and C4B, was considered a prime suspect in the search for causes of psychiatric disorders because it is present in distinct variants within the human population. Therefore, different individuals may have not only variable numbers of copies of the gene, but also unique DNA sequences, causing the gene to work differently.
According to the study results, people with schizophrenia have a C4A gene variant that facilitates synaptic pruning. This is a process in which the brain eliminates weak or redundant connections between neurons as it develops to full maturity in late adolescence and early adulthood. Noticeably, as previously mentioned, the onsets of schizophrenia symptoms occurs in late adolescence and early adulthood. In addition, individuals with schizophrenia have a reduced numbers of synapses in their brain. Thus, the findings related to C4A provide a plausible biological explanation for the onset of schizophrenia.
Bruce Cuthbert, acting director of the National Institute of Mental Health, said in a press release: “This study marks a crucial turning point in the fight against mental illness. It changes the game. Thanks to this genetic breakthrough, we can finally see the potential for clinical tests, early detection, new treatments and even prevention.”