Schizophrenia is known as one of the most common serious mental illnesses. Characterized by a decreased ability to understand reality and hearing voices that do not exist among other things, it occurs in 15-20 people per 100,000 per year (Salleh: 2004). Although techniques to treat it are improving, many of those with the condition suffer from frequent relapse and admission. This in mind, schizophrenia has been thought to largely come from genetic factors. But is this really the case?
By the end of the 20th century, genetic explanations for the origins of schizophrenia were very popular. With some claiming its heritability to be between 80%-85%, others even went as far as to say that it may be 100% genetic, with environmental factors having little or no impact on its incidence (Torrey: 2019).
Although there have been many predictions on the heritability of the condition, as well as the identification of many gene “tags”, a challenge still remains in being able to link these tags to the illness’s symptoms. After all, genes encode proteins, not necessarily the hallucinations, delusions and states of mind that people with schizophrenia face. Thus, to understand how different tagged regions on the genome lead to changes in how brain cells are produced, a series of complex studies have been and are being undertaken.
Despite the progress being made, understanding this process is not so simple. A good example of this is the first gene to have been associated with schizophrenia, known as ZNF804A. Although the protein it produces binds to a genetic tag associated with schizophrenia, it cannot bind to DNA. This means that, although this same schizophrenia genetic tag influences how much ZNF804A may be produced, its function is otherwise mysterious (Tunbridge: 2016).
Meanwhile, the amount to which schizophrenia is associated to genetics seems to be diminishing in academic circles- with academics now estimating its heritability to be closer to 30%, as other possibilities for its causes are becoming apparent (Grohol: 2019).
For example, research centred on our microbiome, or gut bacteria, has become a recent focal point for academia when looking at the causes of the condition. For example, a team of researchers recently found 56 operational taxonomic units (OTUs) exclusively present in the microbiomes of people with schizophrenia. When introduced to healthy mice, they noticed the mice display changes in their behavior. An interesting finding, the research suggests that schizophrenia-related symptoms may be caused by interactions with microbiota gut-brain amino acids and possibly lipid metabolic pathways, rather than genetics alone (Yirka: 2019).
To conclude, although genetic causes for schizophrenia may not be as conclusive as previously thought, research is currently underway to further understand the true extent to which they can be attributed. Meanwhile, other possible causes for the condition, such as gut bacteria, have shifted the focus of the condition’s heritability in favour of being more influenced by our environment.
Salleh, Mohd Razali: Malays Med Sci
Torrey, E.F. et al. Psychiatry Research
Tunbridge, Elizabeth: The Conversation
Yirka, Bob: Medical Xpress
Grohol, John M.: Psych Central