Lecture 4: Genetics of Mental Disorders Flashcards
What is the peak age of onset for schizophrenia?
20.5 years.
What is the peak age of onset for depression?
19.5 years.
What are the peak ages of onset for anxiety?
15.5 years and 30.5 years (two life peaks).
What variations exist in the distribution of anxiety disorders?
Distribution differs across countries and environments, indicating influences beyond genetics.
How can genetic predisposition for mental health disorders be activated?
- Significant brain events, such as:
1) Drugs (e.g., cannabis): can disrupt the dopaminergic system and trigger symptoms.
2) Life factors: Stress & difficult family dynamics.
What are key facts about anorexia nervosa?
- More common in women than men and affects all demographics (not linked to social class).
- Peak age: 15-20 years.
- Causes: strong genetic basis with environmental triggers/modulators.
What distinguishes early-onset Alzheimer’s disease (AD)?
- specific disease-causing genes.
- phenotypic variants are rare but exists.
What are the characteristics of late-onset Alzheimer’s disease (AD)?
- age 75+
- cause - associated with high-risk genes rather than disease-causing genes.
What global variations exist in mental health disorders?
Prevalence and patterns vary globally, influenced by both genetics and environmental factors.
What are the key risk factors for anorexia nervosa?
- Female gender.
- Being from the developed world (thin ideal).
- Migrants from developing to developed countries.
- Living in urban areas.
- Life pursuits emphasizing body image (e.g., gymnastics, fashion modeling).
- Increased genetic heritability and family history (including history of leanness).
- Early menarche (controlling for bodyweight).
- Epigenetic changes to DNA (e.g., Dutch WWII starvation, food repletion, severe stress).
- Low self-esteem.
- High clinical perfectionism.
- Emotional and sexual child abuse.
What are the DSM-5 criteria for anorexia nervosa (AN)?
(1) Restrictive energy intake resulting in significantly low body weight.
(2) Intense fear of weight gain or behaviors preventing weight gain.
(3) Body image disturbance or lack of recognition of the seriousness of low body weight.
What are the two subtypes of anorexia nervosa?
(1) Restriction type: Weight loss through dieting, fasting, or exercise, with no binge eating or purging in the past 3 months.
(2) Binge-eating/purging type: Weight loss through self-induced vomiting, laxatives, or diuretics.
What challenges exist in genetic research for anorexia nervosa?
- Lack of biological markers (e.g., limited measurable parameters like stress hormones).
- Complex interplay of genetic and environmental factors in disease onset.
How are twin studies used to assess genetic vs environmental contributions to AN?
- Identical twins (same genome) are compared to non-identical twins.
- Identical twins: 80% concordance (high genetic contribution).
- Non-identical twins: 46% concordance (higher environmental influence).
What are single nucleotide polymorphisms (SNPs), and how are they used in genetic analysis?
- SNPs are genome-wide tools that map 10 million variants.
- They compare disease cases to controls to identify significant genetic differences.
How is SNP analysis conducted?
- Use identical twins as a reference (same genetic lettering, C/T from parents).
- Compare SNP frequencies between cases and controls.
- Example: A SNP with more “C” than “T” in cases suggests a genetic association with the disease.
- Next, identify significant variants and explore their molecular mechanisms.
Why is responsible communication of genetic findings essential?
- Genes interact with environmental factors; predisposition doesn’t guarantee onset.
- Miscommunication could lead to societal stigma or misuse.
- Emphasizing benefits while addressing complexity is crucial.
What are the genetic findings in anorexia nervosa regarding family risk?
- Female relatives of individuals with AN are 11x more likely to develop AN.
- However, having two parents with AN does not guarantee that the child will develop the disorder.
Why are large sample sizes important in genetic studies like GWAS?
- Smaller GWAS (<10,000 cases) often fail to replicate findings.
- Larger GWAS identified robust signals (e.g., 108 genetic loci in schizophrenia).
- Large sample sizes allow better exploration of genetic variants’ roles in relevant cell types.
What are the psychosocial benefits of genetic findings in eating disorders?
1) Genetic research interests patients and families by validating their experiences.
2) Genetic explanations can relieve blame historically placed on individuals or families.
3) Findings help legitimize the condition as more than just psychological or imagined.
What are the potential challenges of genetic findings in eating disorders?
- Can lead to guilt (e.g., “passing on bad genes”) or fear/fatalism (“I am doomed to develop it”).
- Oversimplifying eating disorders as purely genetic ignores the genetic-environmental interplay.
What are the risk factors for bipolar disorder?
Increased genetic heritability and family history (no real sex difference).
Stressful events (death, accident, robbery).
Negative social support from family or friends.
Social phobia.
PTSD and ADHD.
Drug or alcohol abuse.
Impulsivity.
Suicidal ideation.
What is the heritability of bipolar disorder based on twin studies?
- Heritability ranges from 73-93%, with a mean of 85%.
- Identical twins: 93%.
- Non-identical twins: 73%.
What are the common co-morbidities associated with bipolar disorder?
1) Cardiovascular risks: diabetes, hypertension, kidney disease, smoking, obesity.
2) Psychiatric conditions: ADHD, impulse control issues, anxiety, substance abuse.
