Lecture 22 - Schizophrenia Flashcards
What is the role of gene-environment interactions in common diseases and disorders?
Gene-environment interactions refer to how our genes and our environment work together to influence our health.
While our genetics play a big role in the development of diseases, the rates of these diseases can be very different depending on the culture or time period. This is because environmental factors, like lifestyle, diet, pollution, or modern stressors, which weren’t part of our ancestors’ environments, can contribute to the rise of diseases today. These factors interact with our genes to affect how we get sick or stay healthy.
Give examples of diseases where gene-environment interactions are evident.
Examples include obesity, diabetes, asthma, drug addiction, heart disease, strokes, cancer, late-onset neurodegenerative disorders, depression, and anxiety. These diseases have environmental risk factors that were not present in ancestral environments.
Why are gene variants that protect against diseases increasing in prevalence?
If the environment, lifestyle, and culture remain constant, gene variants that protect against diseases will become more common over generations, eventually reaching a prevalence where everyone has them.
How do “severe” mental disorders like schizophrenia and autism differ from other diseases in terms of gene-environment interactions?
These disorders are highly heritable, but their prevalence does not vary significantly across cultures or history, unlike diseases that show clear gene-environment interactions.
What is the relationship between “severe” mental disorders and reproductive success?
Severe mental disorders, such as schizophrenia and autism, tend to reduce reproductive success, with affected individuals having fewer children (about half as many) compared to others.
Why do harmful, heritable mental disorders like schizophrenia persist despite their negative effects on reproductive success?
Although these disorders are genetic and common, the persistence of harmful alleles in the population is not fully understood, and researchers have not identified clear benefits that offset their harmful effects.
What is known about schizophrenia susceptibility genes?
Hundreds of gene variants associated with a small increase in schizophrenia risk have been identified. The concordance rate for schizophrenia in identical twins is 50%, indicating a genetic predisposition.
How do environmental risk factors influence the development of schizophrenia?
Environmental risk factors have a small overall influence on schizophrenia. The disease is primarily genetically predisposed, with environmental factors playing a minor role.
Why are schizophrenia susceptibility genes so common in the gene pool?
One theory is that some of these genes, in certain combinations, might have offered an evolutionary advantage, such as boosting creativity or problem-solving skills, which could improve reproductive success. However, this theory has not yet been proven, as studies have not consistently found these benefits in the close relatives of people with schizophrenia.
What is the relationship between schizophrenia susceptibility genes and other mental disorders?
The same gene variants that increase the risk of schizophrenia are also linked to bipolar disorder, depression, autism, OCD, and ADHD. These gene variants reflect a general vulnerability to mental illness, not a specific disorder.
What do studies of gene variants across psychiatric conditions show?
Gene variants associated with schizophrenia are also linked to bipolar disorder, depression, OCD, autism, anorexia, and ADHD, suggesting a shared genetic vulnerability across different mental disorders.
Are mental disorders considered discrete, unitary diseases?
No, they are not. Mental disorders have too much heterogeneity within categories, comorbidity across categories, and continuity with normality to qualify as discrete diseases.
What are diagnostic categories based on?
Diagnostic categories are based on clusters of symptoms that tend to appear together, reflecting historical conventions more than biological differences.
How do mental disorder susceptibility genes contribute to mental illness?
These genes do not directly cause mental illness but affect brain development and neural plasticity, slightly altering brain interactions, reducing overall brain function and development.
Do people with similar mental illnesses share the same gene variants?
No, people with similar mental illnesses often do not share the same gene variants, and there is no consistent set of brain peculiarities across them.
How does human brain development work?
Brain development is robust despite unavoidable randomness, as the genome contains redundancies and error-checking mechanisms to ensure healthy brain development and function.
How do gene mutations affect brain development?
Gene mutations can stress brain development, but the robustness of genetic instructions allows variations to accumulate in the population if the mutations are not too severe.
What does body symmetry indicate about genetic instructions?
Body symmetry reflects clear genetic instructions, while random asymmetries suggest developmental instability, which can indicate less robust genetic instructions.
How are intelligence, physical attractiveness, and health related to body symmetry?
These traits have a genetic basis and are correlated with body symmetry, which may indicate neurodevelopmental robustness that can withstand environmental and molecular variations.
What is mutation-selection balance?
Mental illness may result from a combination of gene mutations that slightly disrupt brain networks. Over time, harmful mutations are eliminated by natural selection, but new mutations continually arise.
Should we focus on specific genes for mental illness risk?
No, because half of our genome impacts brain function and development. Mutations anywhere in the genome can increase the risk of developing mental illness.
What is the current usefulness of gene testing for mental illness?
Gene testing is not particularly helpful for preventing or treating psychiatric disorders since most prevention is about avoiding trauma and taking care of oneself.
What lifestyle habits help maintain brain and body health?
Staying active, eating well, reducing stress, maintaining good sleep habits, and limiting alcohol, tobacco, and hard drugs.
What are the future directions for mental illness research?
Researchers aim to develop gene editing techniques, new pharmacological treatments targeting intracellular signaling, and improved brain stimulation strategies, including closed-loop stimulation to correct neural circuit irregularities.
